Diet and fertility: a review

Dietary intake of polyunsaturated fatty acids, their food sources and fertility in females and males: a preconception prospective population-based cohort study

BACKGROUND

Seafood, nuts, and seeds are key dietary sources of polyunsaturated fatty acids (PUFAs), which may benefit reproductive health.

OBJECTIVES

This study aims to investigate associations of periconception dietary intake of PUFA-rich foods and omega-3 and omega-6 PUFAs with fecundability and subfertility in females and males.

METHODS

Among 830 females and 651 males, participating in a population-based prospective cohort study from preconception onwards, we assessed periconception dietary intake at median 12.4-wk gestation (95% range: 10.9, 18.4) and time to pregnancy via questionnaires. Fecundability was defined as the probability of conceiving within 1 mo and subfertility as time to pregnancy ≥12 mo or use of assisted reproductive technology. Cox proportional hazards and logistic regression were used to assess associations between PUFA(-rich foods) with fecundability and subfertility.

RESULTS

In females, PUFA-rich food intake was not significantly associated with fertility. Higher omega-3 PUFA intake, especially docosahexaenoic acid and alpha-linolenic acid, but not omega-6 PUFA, was per standard deviation score (SDS) increase associated with increased fecundability and reduced subfertility. Strongest effects were observed for females in the highest quartile. A lower omega-6 to omega-3 PUFA ratio was associated with increased fecundability and lower subfertility risk [fecundability ratio (FR): 0.92, 95% confidence interval (CI): 0.87, 0.96; odds ratio (OR): 1.14, 95% CI: 1.02, 1.26, per unit increase in omega-6:omega-3 PUFA ratio]. In males, higher intake of nuts/seeds, but not seafood, was associated with increased fecundability and lower subfertility (FR: 1.10, 95% CI: 1.01, 1.20; OR: 0.78, 95% CI: 0.63, 0.97 per SDS increase in nuts/seeds). Strongest effects were present for those who consumed the highest amount. No associations were observed for omega-3 or omega-6 PUFA intake in males.

CONCLUSIONS

In females, higher dietary omega-3 PUFAs intake may benefit fertility. Increased nuts and seeds consumption may improve fertility in males, independent of PUFA intake. These findings suggest potential for gender-specific dietary interventions to support reproductive health.

Knowledge, attitudes, and practices regarding the impact of diet on pregnancy among infertile individuals: a cross-sectional study

BACKGROUND

There is a conspicuous lack of knowledge, attitudes, and practices (KAP) studies directed towards understanding the impact of diet on pregnancy among infertile individuals. Dietary habits can have a certain impact on infertility. To investigates the KAP of infertile individuals regarding the influence of diet on pregnancy.

METHODS

A cross-sectional study was conducted from July 2023 to January 2024 in Beijing, China. A structured questionnaire based on comprehensive literature review and validated by expert consultation was administered to gather demographic information, as well as to assess KAP among individuals experiencing infertility. The Cronbach's α coefficient was 0.897, indicating high internal consistency. Statistical analyses included descriptive statistics, correlation analysis, logistic regression, and structural equation modeling.

RESULTS

A total of 580 participants were included in this study. Of these, 494 individuals (85.17%) were identified as female, while 325 participants (56.03%) reported experiencing infertility for a duration spanning 0 to 3 years. The mean knowledge, attitude, and practice scores were 27.04 ± 9.80 (possible range: 0-46), 21.84 ± 3.24 (possible range: 5-25), and 25.69 ± 4.07 (possible range: 9-45), respectively. Multivariate logistic regression showed that attitude score and aged more than 40 years were independently associated with proactive practice. The structural equation modeling (SEM) analysis revealed a significant direct influence of knowledge on both attitude and practice.

DISCUSSION

Given the identified gaps in knowledge and practice, healthcare providers should prioritize educational interventions targeting infertile individuals, particularly focusing on enhancing awareness and promoting proactive dietary practices to improve pregnancy outcomes.

CONCLUSION

Infertile individuals demonstrated insufficient knowledge, positive attitudes, and passive practices regarding the impact of diet on pregnancy.

CLINICAL TRIAL NUMBER

2022PHB405-001.

Association between the dietary index for gut microbiota and female infertility: The mediation effects of lymphocyte count and red blood cell folate

Previous studies have revealed a the relationship between changes in the gut microbiota composition and female infertility. While the association between the dietary index for gut microbiota (DI-GM) and female infertility remains unstudied. The correlation was investigated with NHANES data from 2013 to 2018, with dietary recall data being used to calculate the DI-GM. Mediation analysis was performed to explore the role of lymphocyte count (LC) and red blood cell (RBC) folate in the DI-GM-induced risk of female infertility risk. Among the 1555 individuals included in our study, 311 were diagnosed with female infertility. According to the weighted binary logistic regression analyses, when all the covariates were adjusted, a negative association was observed between the DI-GM score and the risk of female infertility (OR: 0.80, 95 %CI: 0.74-0.88). After grouping participants by DI-GM score, compared with scores in the lowest quartile (Q1), the scores in Q3 and Q4 of DI-GM score were negatively associated with female infertility in crude and adjusted models, with ORs (95 %CI; P for trend) of 0.44 (0.27-0.70; <0.001); 0.43 (0.28-0.64; <0.001) and 0.43(0.26-0.71; <0.001); 0.41(0.27-0.60; <0.001). Additionally, restricted cubic splines logistic analysis uncovered a nonlinear association between the DI-GM score and the prevalence of female infertility. Mediation analysis indicated that LC and RBC folate mediated 4.64 % and 7.08 %, respectively of the association of the DI-GM scores with risk of female infertility. The nomogram exhibited good performance in this study (AUC 0.70, 95 % CI = 0.67-0.73). Our research revealed that the DI-GM score was negatively related to risk of female infertility. Mediation analyses demonstrated that LC and RBC folate levels significantly mediate the association between the DI-GM and the prevalence of female infertility.

Nutrition and reproductive potential of women in low- and middle-income countries: a systematic review and meta-analysis

INTRODUCTION

Nutrition plays a critical role in key physiological processes related to reproduction. However, there is limited understanding of the impact of nutritional factors and interventions on the reproductive outcomes of women in low- and middle-income countries (LMICs).

METHODS

This systematic review and meta-analysis aimed to synthesise evidence regarding the impact of nutritional factors and interventions on the reproductive outcomes of women in LMICs. Outcomes of interest included fertility and fecundity, menarche and menstrual disorders, miscarriage, stillbirth and live birth. Randomised controlled trials (RCTs) and non-randomised intervention studies with nutritional interventions, and observational cohort studies with nutritional factors, were included. Study selection, data extraction and risk of bias assessment were independently completed by two reviewers. A narrative synthesis of included studies was conducted, and meta-analyses were conducted when feasible.

RESULTS

Systematic search identified 180 studies, including 47 intervention studies and 133 observational cohort studies. From RCTs, there was no clear evidence for an effect of prenatal multiple micronutrient supplementation on the risk of miscarriage (8 RCTs; risk ratio (RR): 0.87; 95% CI 0.75, 1.02; moderate certainty of evidence) or stillbirth (15 RCTs; RR: 0.86; 95% CI 0.73, 1.02; low certainty of evidence). From observational cohort studies, preconceptional obesity was associated with a greater risk of miscarriage (12 studies; RR: 1.27; 95% CI 1.10, 1.47; very low certainty of evidence) and stillbirth (4 studies; RR: 1.66; 95% CI 1.28, 2.14; very low certainty of evidence). Any anaemia during pregnancy was associated with a greater risk of stillbirth (10 studies; RR: 1.26; 95% CI 1.01, 1.58; very low certainty of evidence).

CONCLUSION

This review highlights the importance of ensuring preconceptional nutrition and preventing anaemia during pregnancy for favourable reproductive outcomes. This review calls for randomised controlled trials to evaluate the effectiveness of preconceptional and prenatal interventions on these outcomes.

PROSPERO REGISTRATION NUMBER

CRD42023395937.

High-altitude hypoxia exposure alters follicular metabolome and oocyte developmental potential in women

PURPOSE

To explore the effects of high-altitude hypoxia on the microenvironment of oocyte development and fertilization potential, we compared the metabolomic patterns of follicular fluid from women living in different altitude areas and traced their oocyte maturation and subsequent development.

METHODS

A total of 315 clinical cases were collected and divided into three groups according to their residence altitudes: 138 cases in low-altitude (< 2300 m) group, 100 cases in middle-altitude (2300-2800 m) group and 77 cases in high-altitude (> 2800 m) group. The clinical outcomes were statistically estimated, including hormonal level, oocyte maturation, in vitro fertilization, and embryo development. Meanwhile, a metabolomic analysis was performed on the follicular fluid of women from different groups using ultra-high-performance liquid chromatography and high-resolution mass spectrometry and differential metabolites were analyzed through the KEGG pathway.

RESULTS

The clinical data indicated that the physical condition and reproductive hormone secretion were similar among different groups. Although personalized gonadotropin-releasing hormone strategies were applied, the numbers of antral follicles and obtained oocytes were not impacted by the residence altitude change. In in vitro culture, the maturing rate, fertility rate and cleavage rate of high-altitude group were compared with the other groups. However, the rates of high-quality embryo, formative blastocyst, and available blastocyst were gradually decreased with the rise of residence altitude. Metabolome analysis identified 1193 metabolites in female follicular fluid. Differential analysis indicated that metabolic components in follicular fluid were remarkably changed with the elevation of residence altitude. These differential metabolites were closely related with amino acid metabolism, protein digestion and absorption, oocyte meiosis and steroid biosynthesis.

CONCLUSION

The residence altitude alters the microenvironment of follicular fluid, which could damage the oocyte developmental potential. This study provides diagnostic basis and therapeutic targets for research on female oocyte and embryo development.

Healthy Moms, Healthy Babies: Culinary and Lifestyle Medicine for PCOS and Preconception Health

Purpose of the Research: Women's reproductive health issues represent a major source of burden to quality of life, productivity, and health care cost, with uneven access to care. Foundational interventions based on lifestyle and food as medicine hold promise as one equitable way to improve individual and family health. In this paper, we summarize the lifestyle and culinary medicine approaches to two of the most common reproductive health diagnoses, polycystic ovary syndrome (PCOS) and infertility. Major findings: For women with PCOS and/or infertility, an overall healthy eating pattern, including a whole-food plant-based or Mediterranean diet, carries clear health benefits. Exercise is of benefit in the PCOS population, and likely so for infertility patients as well. Both diagnoses are risk factors for anxiety and/or depression, and so more attention to mental health and behavioral strategies is needed. Given these findings, the notion of lifestyle interventions holds promise, but studies are overall mixed. Conclusions: PCOS and infertility can respond well to lifestyle and culinary interventions. These approaches, currently underutilized, can be implemented widely with minimal cost, and can also improve obstetric, neonatal, and child health outcomes via epigenetic phenomena. More research is needed to elucidate the best target populations and delivery methods for such interventions.

The Association Between Periconceptual Maternal Dietary Patterns and Miscarriage Risk in Women With Recurrent Miscarriages: A Multicentre Cohort Study

OBJECTIVE

To examine the association between periconceptual maternal diet and miscarriage risk among women with recurrent miscarriages.

DESIGN

Prospective multicentre cohort study (Tommy's Net).

SETTING

Three university hospital research centres in the United Kingdom.

POPULATION

1035 women with a baseline history of two or more miscarriages.

METHODS

We analysed baseline dietary data from a 10-item Food Frequency Questionnaire (FFQ). For individual food category analyses, we used multivariable Poisson regression following adjustment for maternal confounders and paternal dietary patterns. For whole diet analyses, ordinal principal component analysis (PCA) was used to identify common dietary patterns. Results were presented as relative risks (RR) with 95% confidence intervals (CI) and accompanying p-values.

MAIN OUTCOME MEASURES

Miscarriage rate, defined as the rate of spontaneous pregnancy loss (< 24 weeks of gestation) relative to the total number of pregnancies (miscarriages and live births).

RESULTS

High consumption of fruit and nuts (almonds and walnuts) was associated with lower miscarriage risk (fruit 226/662 (34.1%) vs. 38/77 (49.4%), RR 0.66, 95% CI 0.51 to 0.85, p = 0.001; nuts 47/152 (30.9%) vs. 220/613 (35.9%), RR 0.73, 95% CI 0.54 to 0.98, p = 0.039). High red meat intake was associated with a possible increase in miscarriage risk (6/12 (50.0%) vs. 165/469 (35.2%), RR 1.86, 95% CI 1.10 to 3.16, p = 0.022). The association with miscarriage risk was unclear for other food groups, including fresh vegetables, white meat, fish, dairy, eggs, soya and chocolate, due to imprecise point estimates. Through PCA, we identified three data-derived dietary patterns. Yet, no distinct relationship emerged between these dietary patterns and miscarriage risk.

CONCLUSIONS

A maternal diet rich in fresh fruits and nuts is associated with a lower miscarriage risk among women with a history of recurrent miscarriage.

TRAIL REGISTRATION

Tommy's Net (ISRCTN17732518) https://www.isrctn.com/ISRCTN17732518. Analysis plan (OSF zp7cs) https://osf.io/zp7cs.

Association between the composite dietary antioxidant index and risk of infertility: Evidence from NHANES 2013-2020 and a Mendelian randomization study

OBJECTIVE

The Composite Dietary Antioxidant Index (CDAI) measures the antioxidant capacity of the diet, which is believed to provide protection against various diseases, including depression, osteoporosis, and papillomavirus infection, by neutralizing harmful oxidative stress. However, the relationship between CDAI and infertility is not well understood. This research aims to explore the potential correlations between CDAI and the risk of infertility.

METHODS

This research harnessed data from the National Health and Nutrition Examination Survey (NHANES) to execute a cross-sectional analysis involving 8263 US women aged 20-45. Each participant was subjected to two distinct 24-h dietary recall interviews. We calculated the CDAI using average daily antioxidant intake. Infertility was assessed using a standardized questionnaire. The association between CDAI and infertility was examined using weighted multiple logistic regression models, while nonlinear correlations were explored through restricted cubic splines. To affirm the robustness of our findings, sensitivity and subgroup analyses were performed using unweighted logistic regression. Additionally, to ascertain the causal influence of circulating antioxidant levels on infertility, a two-sample univariable Mendelian randomization (MR) analysis was conducted, using the inverse variance weighted (IVW) method as the primary analytic approach.

RESULTS

Participants who were infertile exhibited lower CDAI levels compared to their fertile counterparts. When confounding variables were accounted for in the multivariate weighted logistic regression model, an inverse relationship was observed between CDAI and infertility, with the odds ratio for the highest versus lowest quartile being 0.55 (0.33-0.90, P = 0.02). However, the IVW method indicated that genetically predicted elevated levels of CDAI did not significantly correlate with infertility.

CONCLUSION

Cross-sectional observational studies indicate that antioxidants from diets might diminish infertility risks. However, findings from MR studies do not confirm a causal connection. Additional prospective research is required to elucidate this association further.

Randomized controlled trial of 4.0 mg versus 0.4 mg folic acid supplementation: Follow-up of children at 1 year of age

Objective and study design

This 1-year follow-up study reports the results on the health status, visits to the paediatrician and hospitalizations of children born from the women recruited in the main randomized controlled trial (RCT) that investigated the effect of periconception folic acid (FA) supplementation of 4.0 mg/day on reducing adverse reproductive outcomes.

Methods

The health status of livebirths was evaluated by a trained health care provider (HCP) through a phone interview with the paediatrician (at 1-3-12 months of age) and with the parents (at 12 months of age), using a structured data collection form.

Results

Information at 1 year of life could be obtained for 347/376 (92.3 %) newborns included in the original RCT. No statistically significant differences were observed between the two groups regarding weight, health problems, hospitalizations from birth to 1 year of life and developmental milestones, as well as accesses to the emergency ward and parents'worries. Breastfeeding differed significantly at 1, 3 and 12 months of life, with higher proportion of exclusive breastfeeding in the 4.0 mg FA Group.

Conclusion

The findings suggest that the periconception FA supplementation of 4.0 mg/day versus 0.4 mg/day, does not affect the health status and hospitalizations from birth to 1 year of life, as well as normal child's developmental milestones at 1 year of life. The increase in exclusive breastfeeding in the 4.0 mg FA group needs further investigation.

Higher Life's Crucial 9 protects against infertility among U.S. women aged 18-45 years

Objective

Infertility is not only a reproductive issue but is also closely linked to cardiovascular health and other factors. Life's Crucial 9 (LC9) is a set of lifestyle guidelines aimed at improving cardiovascular health, yet its potential association with infertility remains underexplored. This study aims to investigate the relationship between LC9 and infertility, providing new insights and strategies for the prevention and management of infertility.

Methods

This study utilized data from the National Health and Nutrition Examination Survey (NHANES) from 2013 to 2018. Multivariate logistic regression and weighted quantile sum (WQS) regressions were employed to investigate the association between LC9 and infertility. Restricted cubic spline (RCS) analysis explored the linear or non-linear relationship between LC9 and infertility. Interaction analyses were conducted on subgroups to validate the findings.

Results

There was a significant negative association between LC9 and infertility. After adjusting for covariates, for every 10-point increase in LC9, there was a 35% decrease in the prevalence of infertility (P < 0.001). This negative correlation persisted when LC9 was divided into quartiles. Moreover, as LC9 increased, there was a trend towards lower infertility prevalence (P for trend < 0.001). WQS analyses showed consistent associations (OR=0.27, 95%CI: 0.14, 0.53), with sleep health score, psychological health score, and Body mass index score as significant factors. The dose-response curve indicated a linear association between LC9 and infertility, with higher LC9 associated with lower infertility risk.

Conclusion

The results of this study show a strong negative correlation between LC9 and the prevalence of infertility. Clinically, these findings offer hope for infertility patients, suggesting that adherence to a higher LC9 score significantly reduces the risk of infertility. This will provide a new avenue for infertility prevention and management, offering hope and potential relief to infertile patients.

Preconception diet quality and modified natural cycle in vitro fertilisation outcomes

Lifestyle has been associated with in vitro fertilisation (IVF) success rates, but studies on diet and IVF outcomes are inconclusive. We studied associations between adherence to the Dutch guidelines for a Healthy diet 2015 and pregnancy chances among women receiving modified natural cycle in vitro fertilisation (MNC-IVF). This prospective cohort study utilised data from 109 women undergoing MNC-IVF between 2014 and 2018 at University Medical Centre Groningen enrolled in a study examining associations between metabolic profile of follicular fluid and oocyte quality. Adherence to dietary guidelines was assessed by daily food records quantified based on the Dutch Healthy Diet (DHD) 2015 Index. IVF outcomes (i.e. positive pregnancy test, ongoing pregnancy, and live birth) were obtained from patient records. Statistical analyses involved Cox proportional hazard regression analyses while adjusting for maternal covariates age, smoking, and Body Mass Index (BMI), and stratified for treatment, age, BMI, and energy intake. Women were 31.5 ± 3.3 years old, and had a BMI of 23.5 ± 3.5 kg/m2. Higher DHD2015 adherence was linked to a reduced probability of achieving an ongoing pregnancy (HR = 0.77, 95%CI: 0.62-0.96), live birth (HR = 0.78, 95%CI: 0.62-0.98), and showed a non-significant trend towards a lower probability of a positive pregnancy test (HR = 0.85, 95%CI: 0.71-1.01). Associations were particularly present among women undergoing MNC-ICSI (n = 87, p-for-interaction = 0.06), with shorter duration of infertility (n = 44, p-for-interaction=0.06), being overweight (n = 31, p-for interaction = 0.11), and having higher energy intakes (n = 55, p-for-interaction = 0.14). This explorative study suggests inverse trends between DHD2015 adherence and MNC-IVF outcomes, encouraging well-powered stratified analyses in larger studies to further explore these unexpected findings.

Assisted Reproduction Technologies (ART): Impact of Mitochondrial (Dys)function and Antioxidant Therapy

In the last decades, major changes in ecosystems related to industrial development and environmental modifications have had a direct impact on mammalian fertility, as well as on biodiversity. It is widely demonstrated that all these changes impair reproductive function. Several studies have connected the increase of reactive oxygen species (ROS) generated in mitochondria to the recently identified decline of fertility due to various factors, including heat stress. The study of antioxidants, and especially of mitochondria targeted antioxidants, has been focused on identifying more efficient and less toxic therapies that could circumvent fertility problems. These antioxidants can be derived from natural compounds in the diet and delivered to the mitochondria in more effective forms, providing a much more natural therapy. The use of mitochondriotropic diet-based antioxidants in assisted reproductive technologies (ART) may be an important way to overcome low fertility, allowing the conservation of animal biodiversity and productivity. This paper provides a concise review of the current state of the art on this topic, with a particular focus on the antioxidants mitoquinone, AntiOxBEN2, AntiOxCIN4, urolithin A and piperine, and their effects on bovine and other animal species.

Association of Glycemic Index, Glycemic Load, and Carbohydrate Intake with Antral Follicle Counts Among Subfertile Females

BACKGROUND/OBJECTIVES

Few studies have investigated the association of dietary glycemic index (GI), glycemic load (GL), and carbohydrate intake with antral follicle count (AFC). This study aimed to investigate the association of total carbohydrate intake and carbohydrate quality, measured by dietary GI and GL, with ovarian reserve assessed by AFC.

METHODS

This study included 653 females from the Environment And Reproductive Health Study who completed AFC and food frequency questionnaire. Of these, 579 female individuals had a quantifiable AFC in both ovaries and were included in the primary analysis. We estimated average GI and GL for each participant from self-reported intakes of carbohydrate-containing foods and divided participants into tertiles. Poisson regression models were used to quantify the relations of GI, GL, carbohydrates, and AFC while adjusting for potential confounders.

RESULTS

Participants had a median age of 35 y. Compared to participants in the lowest tertile of dietary GI, those in the highest tertile had a 6.3% (0.6%, 12.3%) higher AFC (p, trend 0.03) after adjustment for potential confounders. Stratified analyses revealed that the association between GI and AFC was present only among participants who had not undergone infertility evaluations.

CONCLUSIONS

A higher dietary GI was associated with a higher AFC. Subgroup analyses among individuals who had not had a diagnostic evaluation of infertility before joining the study suggest that high-glycemic carbohydrates may be related to PCOM.

Multivitamin Supplementation and Fertility Outcome: A Retrospective Single-Center Cohort Study and the Clinical and Medicolegal Value of Nutritional Counseling

Resveratrol can beneficially affect growth and follicle development and lead to improved sperm function parameters in pre-clinical studies, while information from clinical studies is still inconclusive. This study aims to evaluate the biological and clinical impact of a resveratrol-based multivitamin supplement on level II assisted reproduction cycles (IVF and intracytoplasmic sperm injection [ICSI]). A retrospective, case-control study, involving 70 infertile couples undergoing IVF/ICSI cycles, was conducted at the Assisted Reproductive Center, Obstetrics and Gynecology Unit-Villa Sofia-Cervello Hospital in Palermo. The study group underwent pre-treatment with a daily nutraceutical based on resveratrol, whereas the control group received 400 mcg/day of folic acid. Primary endpoints to be evaluated were the number of mature follicles developed (>16 mm), total oocytes and Metaphase II (MII) oocytes retrieved, fertilization rate, number of embryos/blastocysts obtained, and semen quality. Secondary objectives in our evaluation were the duration and dosage of gonadotropins, the starting dose, the number of blastocysts to be transferred and frozen, implantation rate, and, ultimately, biochemical and clinical pregnancy rates. In the study group, a significantly higher number of mature follicles, oocytes, and MII oocytes were collected compared to the control group. In the study group, a higher fertilization rate as well as higher numbers of cleavage embryos per patient, blastocysts per patient, and frozen blastocysts were obtained. In the study group, a shorter administration time and lower dosages of gonadotropins required to reach follicle maturity were also observed compared to controls, with fewer dose adjustments during stimulation compared to the starting dose. No significant differences were found in biochemical or clinical pregnancy rates. A 12-month period of dietary supplementation with a resveratrol-based multivitamin nutraceutical leads to better biological effects on ICSI cycles.

Data Mining of Infertility and Factors Influencing Its Development: A Finding From a Prospective Cohort Study of RaNCD in Iran

Background and Aims

Infertility, as defined by the World Health Organization, is the inability to conceive after 12 months of regular, unprotected intercourse. This study aimed to identify factors influencing infertility by applying data mining techniques, specifically rule-mining methods, to analyze diverse patient data and uncover relevant insights. This approach involves a thorough analysis of patients' clinical characteristics, dietary habits, and overall conditions to identify complex patterns and relationships that may contribute to infertility.

Methods

In this study, we examined the impact of lifestyle factors on infertility using machine learning and data mining techniques, specifically Association Rules. The study included a total of 4437 women who participated in the Ravansar Non-Communicable Disease Cohort study. Among the remaining participants, 434 were infertile. We utilized 38 variables to generate the relevant association rules.

Results

As a result, the analysis reveals that 97% of infertile women are likely to cook for more than 2 h and engage in standing activities. Additionally, 94% of infertile women are likely to have central obesity. Infertile women also have a 73% chance of reusing cooking oil and a 74% chance of consuming fried food at least once a week. The likelihood of infertility increases to 98% among women who use more than 24 eggs per month and to 97% among those who consume moldy jam or syrup. The evaluation of these associations was further supported by measures of support, confidence, and lift.

Conclusion

This study showed that key lifestyle factors linked to infertility, underscoring the role of lifestyle in reproductive health. These findings suggest that targeted interventions and lifestyle changes may help reduce infertility rates. Further research is needed to confirm these associations and investigate the underlying mechanisms.

Vitamin B12 is correlated with insulin resistance and metabolism disorder markers in women with recurrent pregnancy loss

OBJECTIVES

Recurrent pregnancy loss (RPL) seriously affects women's reproductive and mental health, and the incidence has increased in recent years. Insulin resistance (IR) acts as a significant contributing factor to RPL. Studies suggest that vitamin B12, folate intake, and homocysteine are correlated with IR, but the exact nature remains controversial and requires further investigation. In this study, we aimed to assess the levels and correlations between vitamin B12-folate-homocysteine and insulin resistance in RPL patients.

STUDY DESIGN

73 control subjects and 256 RPL patients (144 RPL patients without IR and 112 RPL patients with IR) were included in this observational retrospective cross-sectional study. The differences in vitamin B12, folate, and homocysteine levels between RPL patients with and without IR were analyzed using a Student's t-test. Pearson correlations were utilized to examine the correlation between vitamin B12-folate-homocysteine and glucose and lipid metabolism parameters. Multivariable linear regressions were used to assess the independent correlation of each factor with HOMA-IR.

RESULTS

Compared to the control subjects, RPL patients exhibited lower vitamin B12 (p < 0.001) and folate (p < 0.001), and higher homocysteine (p = 0.001). RPL patients with IR described decreases in vitamin B12 (p = 0.003) and folate (p = 0.028), and increases in homocysteine (p = 0.033) as RPL patients without IR. Vitamin B12 in RPL patients was significantly negatively correlated with homocysteine (r = -0.348, p < 0.001), HOMA-IR (r = -0.214, p < 0.001), BMI (r = -0.160, p = 0.017), TG (r = -0.148, p = 0.039) and CHO (r = -0.149, p = 0.038) and positively correlated with folate (r = 0.217, p < 0.001). In multivariable linear regressions, after adjusting for age, strong correlations were observed between vitamin B12 (β = -0.197, p = 0.010), BMI (β = 0.466, p < 0.001), and HOMA-IR in RPL patients.

CONCLUSION

Vitamin B12 is significantly correlated with IR in RPL patients. Circulating vitamin B12-folate-homocysteine metabolism could be a window of the pathological process of IR, obesity, and lipid metabolism disorders in RPL patients.

The role of diet and food supplements in infertility management in the Eastern Mediterranean Region: A narrative review

According to the World Health Organization, 17.5% of the population suffers from infertility. This demonstrates the critical need to expand access to high-quality reproductive care and increase our understanding of the factors that contribute to this issue. This review aims to summarize findings and gaps in the literature regarding diet-related factors and infertility among the Eastern Mediterranean couples poorly studied compared to other populations. The literature search was conducted using PubMed and Scopus databases from January 2012-July 2023. In total, 112 papers described the influence of diet and supplementation on natural and artificial reproductive outcomes in the Eastern Mediterranean Region and were found eligible for the review synthesis. For men, a diet rich in red meat, fatty foods, whole grains, and low in fish, poultry, low-fat dairy products, and vegetables have a positive effect on sperm count. For women, maintaining a healthy weight is crucial for their fertility. Overall, various vitamins and supplements significantly enhance gametes quality, hormonal balance, and antioxidant capacity, despite the results not being consistent across all studies. The findings highlight distinct dietary patterns that mitigate or exacerbate infertility risks, considering macro and micronutrients. Studies unevenly describe potential risk factors, underscoring the need for further exploration across diverse populations.

The Contribution of Precision Nutrition Intervention in Subfertile Couples

BACKGROUND/AIM

Subfertility is characterized by a decrease in reproductive efficiency, which can result in delayed pregnancy, and affects one in six individuals during their lifetime. The present narrative review aims to evaluate the contribution of precision nutrition to changes in fertility in subfertile couples.

METHODS

The literature review was carried out through bibliographic research in the PubMed, Scopus, SciELO and Google Scholar databases. The following search criteria were applied: (1) original articles and narrative, systematic or meta-analytic reviews, and (2) the individual or combined use of the following keywords: "genetic variation", "nutrigenetics", "precision nutrition", "couple's subfertility", and "couple's infertility". A preliminary reading of all the articles was carried out, and only those that best fit the themes and subthemes of the narrative review were selected.

RESULTS

Scientific evidence suggests that adherence to a healthy diet that follows the Mediterranean pattern is associated with increased fertility in women and improved semen quality in men, better metabolic health and reduced levels of inflammation and oxidative stress, as well as maintaining a healthy body weight. The integration of different tools, such as nutrigenetics, predictive biochemical analyses, intestinal microbiota tests and clinical nutrition software, used in precision nutrition interventions can contribute to providing information on how diet and genetics interact and how they can influence fertility.

CONCLUSIONS

The adoption of a multidisciplinary and precision approach allows the design of dietary and lifestyle recommendations adapted to the specific characteristics and needs of couples with subfertility, thus optimizing reproductive health outcomes and achieving successful conception.

Structural equation modeling of dietary patterns and association with vitamin D levels in children aged 9-16 years in Guangzhou, China

Background

Vitamin D deficiency and insufficiency represent critical public health concerns on a global scale. Due to the increase in indoor activities, the role of dietary intake of vitamin D has become increasingly prominent. However, previous studies have focused solely on a single food item.

Objectives

This study aimed to identify dietary patterns among school-aged children in rural areas of Guangzhou, China, and to explore their association with vitamin D levels.

Methods

A total of 2,346 children aged 6-17 years were included in this cross-sectional study. Demographic, lifestyle, and dietary data were collected through structured questionnaires. Dietary patterns were identified using factor analysis, while linear regression and structural equation modeling were employed to analyze the relationship between these patterns and vitamin D levels.

Results

Three distinct dietary patterns emerged: a fruits and vegetables pattern, high-protein pattern, and snack pattern. Analysis revealed that a higher adherence to the fruits and vegetables dietary pattern was associated with lower vitamin D levels. Conversely, among girls, a stronger preference for the high-protein dietary pattern was positively correlated with higher vitamin D levels.

Conclusion

The fruits and vegetables pattern emerged as a risk factor for inadequate internal vitamin D levels. In girls, the high-protein pattern functioned as a protective factor. These findings offer valuable insights and policy recommendations for enhancing the health status of children in rural communities.

The association between dietary diversity and patterns in Chinese university students with abnormal uterine bleeding: a cross-sectional study

BACKGROUND

Abnormal uterine bleeding (AUB) is a common gynecological issue during reproductive years. Researches on how dietary diversity and patterns influence AUB in Chinese university students are limited, with some studies not clearly defining irregular menstruation. This research investigated the incidence of AUB according to the International Federation of Gynecology and Obstetrics criteria and sought to identify preventative factors via online questionnaires.

METHODS

Food intake was assessed via factor analysis. This study analyzed the relationships among the dietary diversity score (DDS), dietary patterns, and AUB via univariate and multivariate binary logistic regression models and generalized additive models.

RESULTS

The sample consisted of 698 students, with 434 (62.2%) having experienced AUB. Among them, 87 (20.05%) reported abnormal frequency, 250 (57.60%) reported irregular menstrual cycle, 41 (9.45%) reported prolonged duration, and 268 (61.75%) reported abnormal flow volume. A 1-unit increase in the DDS was linked to a 22% lower risk of AUB (odds ratio 0.78, 95% CI: 0.67, 0.90). A high DDS (≥ 6) was consistently associated with a lower risk of AUB across all the models. Using a two-piecewise linear regression model and recursive algorithm, a nonlinear, reverse L-shaped relationship was identified between the "low fat plant-based" dietary pattern factor score (FAC4) and AUB, with an inflection point of 1.45. Before this point, FAC4 had a protective effect on AUB (odds ratio 0.42, 95% CI: 0.21, 0.84).

CONCLUSIONS

Our study underscores the importance of a varied diet as a preventive measure for AUB, utilizing a DDS to quantify the relationship between dietary diversity and AUB. According to our findings, higher dietary diversity and moderate adherence to a "low fat plant-based" dietary pattern may be significant protective factors against AUB in university students.

The Impact of Minerals on Female Fertility: A Systematic Review

Female fertility and reproductive system disorders are influenced by a complex interplay of biological, physiological, and environmental factors. Minerals have emerged as crucial yet often overlooked elements that impact fertility and the prevalence of reproductive system disorders.

BACKGROUND/OBJECTIVES

This review aims to provide a comprehensive overview of the multifaceted role of minerals in female fertility, focusing on key areas such as oocyte quality, ovulation, embryo development, oxidative stress, miscarriage, hormonal regulation, environmental exposure, and in-vitro fertilization (IVF) outcomes.

METHODS

A systematic review was conducted, focusing on randomized controlled trials (RCTs), prospective cohort studies, case-control studies, nested case-control, and observational studies examining mineral supplementation and nutrition in women planning pregnancy or utilizing assisted reproduction technologies (ARTs). Relevant literature was sourced from multiple electronic databases, including PubMed, Scopus, Google Scholar, Web of Science, and the Cochrane Library, using keywords related to minerals and female fertility. The quality of studies was assessed using the Newcastle-Ottawa Scale (NCO) for non-randomized studies and the Risk of Bias (RoB) tool for RCTs. This systematic review has been registered on PROSPERO (registration number is CDR 42024547656).

RESULTS

From an initial pool of 20,830 records, 39 articles met the inclusion criteria and were analyzed. The studies addressed various reproductive outcomes influenced by minerals: embryo development, oocyte quality, oxidative stress, miscarriage, hormonal regulation, IVF outcomes, environmental exposure, and minerals as biomarkers. The analysis revealed that minerals like selenium, zinc, and copper are essential for maintaining reproductive health, while exposure to toxic metals such as cadmium and lead is detrimental.

CONCLUSIONS

This review highlights the crucial role of both mineral supplementation and serum mineral status in female fertility. The findings provide key insights for clinicians to improve reproductive health through targeted mineral intake and monitoring. Further research is needed to refine guidelines for supplementation and serum levels in women with fertility issues.

Dietary phytosterols induce infertility in female mice via epigenomic modulations

Dietary modifications to overcome infertility have attracted attention; however, scientifically substantiated information on specific dietary components affecting fertility and their mechanisms is limited. Herein, we investigated diet-induced, reversible infertility in female mice lacking the heterodimer of ATP-binding cassette transporters G5 and G8 (ABCG5/G8), which functions as a lipid exporter in the intestine. We found that dietary phytosterols, especially β-sitosterol and brassicasterol, which are substrates of ABCG5/G8, have potent but reversible reproductive toxicities in mice. Mechanistically, these phytosterols inhibited ovarian folliculogenesis and reduced egg quality by enhancing polycomb repressive complex 2-mediated histone H3 trimethylation at lysine 27 in the ovary. Clinical analyses showed that serum phytosterol levels were significantly and negatively correlated with the blastocyst development rate of fertilized eggs in women undergoing in vitro fertilization, suggesting that phytosterols affect egg quality in both humans and mice. Thus, avoiding excessive intake of certain phytosterols would be beneficial for female reproductive health.

Association between serum unsaturated fatty acids levels and infertility among American women from the National Health and Nutrition Examination Survey 2013-2014

BACKGROUND

Some research indicates that unsaturated fatty acids (UFAs) in the diet could enhance reproductive outcomes in infertile women. However, other research holds different views, possibly due to differences in the conversion rates of UFAs from various foods and bioavailability in the body. Therefore, this research examined the link between serum UFAs and infertility issues.

METHODS

This research included reproductive-age women participating in the 2013-2014 American National Health and Nutrition Examination Survey (NHANES). Serum levels of four UFAs, including palmitoleic acid (16:1n-7), vaccenic acid (18:1n-7), oleic acid (18:1n-9), and linoleic acid (18:2n-6) were measured through gas chromatography-mass spectrometry. Infertility data was collected by affirmative responses to targeted questionnaire items. Associations between serum UFA levels and infertility were evaluated utilizing Poisson regression models and smooth curve fitting methods. Sensitivity analysis was also conducted.

RESULTS

This study included 535 women, aged between 18 and 45. Poisson regression analysis, both adjusted and unadjusted for confounders, revealed no associations between palmitoleic acid, vaccenic acid, oleic acid, or linoleic acid and female infertility (all P > 0.05). However, four UFAs all showed non-linear relationships with infertility in smooth curve fitting analysis. Sensitivity analysis confirmed the stability of the findings.

CONCLUSION

This research established non-linear associations between serum UFAs and infertility in American women. Specifically, maintaining appropriate serum levels of these UFAs may lower infertility risk. These findings offer new insights and practical dietary recommendations for improving female fertility.

Supplementation practices among pregnant women and those trying to conceive: a population-representative survey in Vancouver, Canada

Dietary supplements including vitamins, minerals, and natural health products are commonly consumed by those aiming to optimize fertility and pregnancy outcomes. The aim of this survey was to describe supplementation practices among individuals who were pregnant or trying to conceive in Vancouver, Canada. An online survey was conducted among 500 individuals who were pregnant (n = 250) or trying to conceive (n = 250). Participants met a substantial proportion of vitamin and mineral recommendations through supplements alone. Exceptions included calcium, magnesium, and choline, with median (interquartile range (IQR)) supplementation doses reported by those who were pregnant and trying to conceive, respectively, of: 250 (200 and 250 mg) and 250 (200 and 250 mg), 50 (50 and 75 mg) and 50 (50 and 90 mg), and 53 (10 and 150 mg) and 55 (10 and 100 mg), as compared to perinatal recommendations of 1000 mg/day (calcium), 350 mg/day (magnesium), and 450 mg/day (choline). Conversely, median (IQR) doses of folate reported by those who were pregnant and trying to conceive, respectively, were: 1000 (780 and 1000 µg) and 1000 (800 and 1000 µg), with ∼70% overall (337/471) reporting doses ≥1000 µg (the tolerable upper intake level). Most participants (451/500; 90%) reported supplementation with a prenatal multivitamin; of these, 83% reported that supplementation occurred daily. Overall, as diet was not considered, we cannot ascertain whether recommendations for calcium, magnesium, and choline were met through the combination of supplements and foods; however, we believe that additional supplementation with choline may be required to meet recommendations in pregnancy. Excessive folate supplementation has been previously identified as a concern throughout North America; here, we provide further evidence for excessively high doses consumed via supplements.

Associations of periconception dietary glycemic index and load with fertility in women and men: a study among couples in the general population

BACKGROUND

The dietary glycemic index (GI) and load (GL) reflect carbohydrate quality and quantity, potentially impacting fertility through modulation of insulin sensitivity and generation of oxidative stress. While fertility is influenced by both women and men, reproductive research often emphasizes maternal factors. We first examined periconception dietary intake in both women and male partners, and subsequent associations of dietary GI and GL with fecundability and subfertility.

METHODS

Among 830 women and 651 male partners, participating in a population-based prospective cohort study from preconception onwards, we assessed periconception dietary intake and calculated GI and GL, using a food frequency questionnaire (FFQ) at median 12.4 weeks gestation (95% range 10.9, 18.4). Information on time to pregnancy was obtained through questionnaires, with subfertility defined as a time to pregnancy ≥ 12 months or use of assisted reproductive technology.

RESULTS

In the periconception period, mean energy intake in women was 1870 kcal (SD: 500; 46% carbohydrates, 16% protein, 33% fat; dietary GI 56.2 (SD: 3.5) and GL 141.4 (SD: 67.4)). Mean energy intake in men was 2350 kcal (SD: 591; 43% carbohydrates, 16% protein, 33% fat; dietary GI 56.8 (SD: 3.2) and GL 156.7 (SD: 75.4)). Median time to pregnancy was 4.8 months (IQR: 1.2, 16.4), with 30.6% of 830 women experiencing subfertility. Dietary GI and GL were not associated with fertility outcomes in women. In men, higher dietary GI and GL across the full range were associated with decreased fecundability, after adjusting for socio-demographic and lifestyle factors, as well as dietary GI or GL of female partners [FR: 0.91, 95% CI 0.83, 0.99; FR: 0.90, 95% CI 0.81, 0.99, per SDS increase in dietary GI and GL, respectively]. When assessing the combined influence of dietary GI clinical categories in women and men, both partners adhering to a low GI diet tended to be associated with increased fecundability, but not with subfertility risk.

CONCLUSIONS

Suboptimal periconception carbohydrate intake may be negatively associated with male fertility, but not with fertility outcomes in women. Further studies are needed to assess whether a lower GI and GL diet is a feasible lifestyle intervention to improve couples fertility.

Association between methylenetetrahydrofolate reductase C677T polymorphisms and male oligozoospermia, asthenozoospermia or oligoasthenozoospermia: a case-control study

Mutation of methylenetetrahydrofolate reductase (MTHFR) C677T leads to the decrease of folate utilization and the impairment of spermatogenesis. This study attempts to investigate the association between MTHFR C677T polymorphisms and nonobstructive oligozoospermia, asthenozoospermia or oligoasthenozoospermia in the Chinese population. The study cohort comprised 189 patients diagnosed with oligozoospermia, asthenozoospermia or oligoasthenozoospermia, and 626 controls based on clinical examinations. The MTHFR c.677 genotype of all subjects was determined by fluorescence staining in situ hybridization and the significance of different genotype frequencies was further analyzed by Chi-square test. The results showed that the frequency of MTHFR 677 CT genotype in the oligozoospermia, asthenozoospermia and oligoasthenozoospermia group was 33.3%, 38.3% and 44.0% respectively, whereas it was 47.3% in the control group. The P value of Chi-square test was 0.070, 0.103 and 0.654, respectively. The frequency of MTHFR 677 TT genotype in the oligozoospermia, asthenozoospermia and oligoasthenozoospermia group was 31.1%, 11.7% and 18.0% respectively, while that in the control group was 19.5%. The P value of Chi-square test was 0.061, 0.070 and 0.066, respectively. Collectively, there is a weak association between MTHFR C677T polymorphisms and oligozoospermia, asthenozoospermia or oligoasthenozoospermia within the current Chinese population cohort.

Expression Profiles of Fatty Acid Transporters and the Role of n-3 and n-6 Polyunsaturated Fatty Acids in the Porcine Endometrium

Fatty acids (FAs) are important for cell membrane composition, eicosanoid synthesis, and metabolic processes. Membrane proteins that facilitate FA transport into cells include FA translocase (also known as CD36) and FA transporter proteins (encoded by SLC27A genes). The present study aimed to examine expression profiles of FA transporters in the endometrium of cyclic and early pregnant gilts on days 3 to 20 after estrus and the possible regulation by conceptus signals and polyunsaturated FAs (PUFAs). The effect of PUFAs on prostaglandin (PG) synthesis and transcript abundance of genes related to FA action and metabolism, angiogenesis, and immune response was also determined. Day after estrus and reproductive status of animals affected FA transporter expression, with greater levels of CD36, SLC27A1, and SLC27A4 observed in pregnant than in cyclic gilts. Conceptus-conditioned medium and/or estradiol-17β stimulated SLC27A1 and CD36 expression. Among PUFAs, linoleic acid decreased SLC27A1 and SLC27A6 mRNA expression, while arachidonic, docosahexaenoic, and eicosapentaenoic acids increased SLC27A4 transcript abundance. Moreover, arachidonic acid stimulated ACOX1, CPT1A, and IL1B expression and increased PGE2 and PGI2 secretion. In turn, α-linolenic acid up-regulated VEGFA, FGF2, FABP4, and PPARG mRNA expression. These results indicate the presence of an active transport of FAs in the porcine endometrium and the role of PUFAs as modulators of the uterine activity during conceptus implantation.

Influence of Mediterranean Diet on Sexual Function in People with Metabolic Syndrome: A Narrative Review

Metabolic syndrome (MS), a cluster of cardiometabolic disorders, and sexual dysfunction are two conditions that impact a large proportion of the general population. Although they can occur independently, they are frequently linked and significantly affect people's quality of life. In recent years, research has increasingly focused on the importance of diet, particularly the Mediterranean diet (MD), in modulating sexual function due to its anti-inflammatory, antioxidant, and vasodilatory properties. In this narrative review, we examined the relationship between MS and sexual function in both men and women, with a special emphasis on the MD's therapeutic efficacy in improving sexual dysfunction. In men, MD has been shown to ameliorate erectile dysfunction, as well as several sperm parameters, perhaps leading to improved fertility. On the other hand, adherence to MD has been demonstrated to partially recover several sexual dysfunctions in women, such as those related to their menstrual cycle, menopause, endometriosis, and polycystic ovary syndrome. These favorable effects of MD have been demonstrated in both sexes also among people affected by MS. However, more targeted studies are needed to validate these data for different dietary approaches as well.

Dietary Glycemic Index and Load and Semen Quality: A Cross-Sectional and Prospective Analysis within the FERTINUTS Trial

PURPOSE

Infertility is a global health issue and nutrition plays a significant role in fertility outcomes. We aimed to investigate the cross-sectional and prospective associations of glycemic index (GI) and glycemic load (GL) with semen quality parameters in a cohort of healthy young men.

MATERIALS AND METHODS

The study included 106 men aged 18-35 years from the FERTINUTS trial. Dietary intake was estimated through 3-day dietary records and several semen parameters were assessed. Multivariable linear regression analysis with the Least Absolute Shrinkage and Selection Operator (LASSO) approach was employed.

RESULTS

The cross-sectional analysis revealed positive associations between GI and GL and total sperm count, sperm concentration, and total motility. In the prospective analysis, baseline GI was associated with increases in pH, vitality, immotile sperm or abnormal midpiece and decreases in total sperm count and motility. Conversely, GL was positively associated with changes in vitality and total sperm count.

CONCLUSIONS

While these findings suggest that GI may have adverse effects on several sperm quality parameters, the results were not consistently observed in the cross-sectional analysis. However, GL was consistently associated with better sperm quality in both analyses. The impact of carbohydrate quality and quantity on fertility remains uncertain and larger prospective studies are needed.

Mass spectrometry of water-soluble vitamins to establish a risk model for predicting recurrent spontaneous abortion

The adverse pregnancy outcomes, including recurrent spontaneous abortion (RSA), are strongly correlated with water-soluble vitamins, but how to predict RSA occurrence using them remains unsatisfactory. This study aims to investigate the possibility of predicting RSA based on the baseline levels of water-soluble vitamins tested by ultra-liquid chromatography-tandem mass spectrometry. A total of 918 pregnant women was consecutively enrolled in this cross-sectional study. According to the miscarriage numbers, they were divided into normal first pregnancy (NFP, n = 608), once spontaneous abortion (OSA, n = 167), and continuous spontaneous abortion (CSA, n = 143) groups. The Cox proportional-hazards regression model was employed to establish a risk model for predicting RSA. The RSA occurrence was 6.54% in overall pregnant women, with a prevalence of 12.57% in the OSA group and 27.27% in the CSA group. Significant differences were observed in baseline deficiencies of vitamin B3, B5, B6, and B9 among NFP, OSA, and CSA groups (χ2 = 12.191 ~ 37.561, all P < 0.001). Among these vitamins, B9 (HR = 0.89 and 0.88, all P < 0.001) and B6 (HR = 0.83 and 0.78, all P < 0.05) were identified as independent factors in both the OSA and CSA groups; whereas B5 was identified as an additional independent factor only in the CSA group (HR = 0.93, P = 0.005). The Cox proportional-hazards model established using these three vitamins exhibited poor or satisfactory predictive performance in the OSA (Sen = 95.2%, Spe = 39.0%) and CSA (Sen = 92.3%, Spe = 60.6%) groups, respectively. However, B5, B6, and B9 compensatory levels were not associated with RSA occurrence (all P > 0.05). Our study presents a highly sensitive model based on mass spectrometry assay of baseline levels in B vitamins to predict the RSA occurrence as possible.

Mercury, natural fertility and outcomes of assisted reproduction: A systematic review

The primary route of mercury exposure for the general population is through consumption of contaminated seafood. There is a biological basis for an adverse effect of mercury exposure on human fertility. The goal of this review was to evaluate the existing literature on the association between mercury and pregnancy, among men and women attempting to conceive with and without assisted reproductive technology (ART). Systematic searches were performed in PubMed, EMBASE, Scopus and Web of Science for papers published up to March 2023 with no early date restriction, only including studies with a biomarker measurement of mercury exposure. We identified 11 studies examining mercury and natural fertility and 12 studies examining mercury and outcomes of assisted reproduction (implantation or clinical pregnancy). The accumulated evidence provides some support for a null association between bodily mercury concentrations and natural fertility among women, however, a large proportion of studies did not report adjusted estimates or were extremely imprecise. The majority of studies of natural fertility were also cross-sectional in nature. There was no evidence for an inverse or null association between mercury and natural fertility among men, or mercury and ART outcomes among men or women. In spite of biological plausibility, the existing evidence includes studies that are imprecise and often conflicting and does not allow us to make definitive conclusions on the associations of mercury exposure with successful pregnancy. Additional, larger studies are warranted, especially among individuals with high concentrations of mercury exposure as these individuals may be underrepresented in the current literature.

Advances in DNA methylation of imprinted genes and folic acid regulation of growth and development

DNA methylation is closely related to folate levels and acts as a mechanism linking developmental disorders to chronic diseases. Folic acid supplementation can impact DNA methylation levels of imprinted genes crucial for neonatal development. Imprinted genes are vital for regulating embryonic and postnatal fetal growth. This review summarizes imprinted genes, DNA methylation, folic acid's influence on growth and development and their correlation. It aims to provide a comprehensive overview of research advancements on imprinted genes, DNA methylation and folic acid regulation concerning growth and development.

The Effect of Nutrient Supplementation on Female Fertility: A Systematic Review

Assisted reproductive technologies (ART) have improved infertility treatment but reproductive outcomes remain challenging. Nutrient supplementation is being explored to enhance pregnancy rates, increase live birth rates, and reduce miscarriage rates in females undergoing ART. Nutrients like folic acid, omega-3 fatty acids, and antioxidants have shown potential benefits, yet conflicting results exist. Live birth rates may also be influenced by nutrient supplementation, with coenzyme Q10 and vitamin D showing promise. Miscarriage rates may be reduced with nutrients such as vitamin D, omega-3 fatty acids, and antioxidants, although more research is needed for definitive conclusions. Scientific and medical literature databases such as Cochrane Library, PubMed, and Web of Science were queried to identify relevant English publications adhering to predetermined inclusion and exclusion criteria. Various reproductive metrics, encompassing biochemical pregnancy rate, clinical pregnancy rate, ongoing pregnancy rate, implantation rate, live birth rates, and miscarriage rates, were assessed as clinical endpoints. The study population included 996 female subjects receiving ART. Two studies performed investigations on subjects diagnosed with unexplained infertility, two studies specifically included polycystic ovary syndrome patients, and five studies did not provide any specific information on the type of infertility or subfertility. All studies reported on the clinical/ongoing pregnancy rate, among which four included studies observed a significantly higher rate. Out of the four studies that reported on implantation rates, three found significantly higher rates in treatment groups. Out of the three studies that reported on biochemical pregnancy rates, two studies found significantly higher rates in treatment groups. With respect to the clinical outcomes that were studied in this analysis, variable effects of nutritional supplementation on reproductive parameters were observed. Some studies reported significantly higher rates of clinical/ongoing pregnancy, implantation, biochemical pregnancy, and live birth, while no significant difference was found in miscarriage rates.

Nutritional aphrodisiacs: Biochemistry and Pharmacology

In 2022, the global prevalence of erectile dysfunction (ED) was estimated to be at least 150 million cases. This number is greatly suspected to be underestimate as most men withhold information about ED. Also, about 15% of world population have infertility troubles, and male factors are responsible for almost half of these cases. Studies have shown that the quality of semen has decreased in the past several decades owing to various health factors and environmental toxicants. The current medical interventions involve the inhibition of phosphodiesterase 5 which suffer from serious side effects and costly. One of the popular and most sought interventions are the natural and nutritional remedies as they are foods in essence and potentially with no harm to the body. Therefore, the goal of this paper is to provide a review of the most common nutritional aphrodisiacs with increasing libido and fertility highlighting the potential active constituents as well as the underlying mechanisms.

Promoting empowerment or intensifying reproductive burden? Accounts of preconception health adjustments among women trying to conceive

OBJECTIVE

Women's preconception health is increasingly viewed as playing a critical role in pregnancy and birth outcomes and is becoming an increasing focus of public health messages within the UK and internationally. However, little is known about how women respond to and are impacted by preconception health messages as they try to conceive a baby.

METHODS

Reflexive Thematic Analysis was used to analyse 193 responses from women in the UK to a qualitative survey on experiences of trying to conceive. As part of the survey women were asked to reflect on their engagement with preconception health practices.

RESULTS

Three themes were generated: 1) Being fit for conception; 2) Preconception health and emotional labour, and 3) Interrogating preconception health expectations.

CONCLUSION

The findings demonstrate that whilst engagement with preconception health changes was empowering for some, more troubling implications included: heightened self-surveillance, stress, risks to wellbeing, and feelings of responsibility for poor outcomes. This demonstrates the importance of considering the unintended consequences of preconception health messaging in the shape of increased 'reproductive burden'. Furthermore, future development of preconception health policy and practice must also consider women's access to psychological support when trying to conceive.

Real-world survey of eating attitudes and spending behaviors related to healthy foods/supplements in women seeking to become pregnant

BACKGROUND & AIMS

Since 2022, fertility treatments have been partially covered by insurance in Japan. Women who wish to become pregnant may explore various means of conception as fertility treatments have shown low success rates. Therefore, we aimed to clarify the state of knowledge, behavior, and attitudes toward health foods among women who are actively trying to become pregnant.

METHODS

A web-based research company surveyed the eating attitudes and behaviors towards healthy foods of 900 women seeking to become pregnant. Regression analysis for the total amount spent on pregnancy was conducted, with "amount spent on actions undertaken to conceive" as the dependent variable. Multiple regression analysis on actions undertaken to conceive was performed using age, family income, body mass index, duration of hospital visits, duration of actions undertaken to conceive, cumulative amount incurred to conceive, awareness of dietary guidelines, adherence to dietary practices, number of types of health foods and supplements, whether participants considered consumption of nutritious foods and supplements to be important, and cumulative amount spent on healthy foods and supplements. The effect size for the Chi-square test was determined with Cramer's coefficient of association.

RESULTS

Increasing age was associated with a longer time to conceive, longer hospital visits, higher conception costs (including fertility treatment), and a higher intake of healthy food products. The number of healthy food types had the greatest impact on the cost incurred to conceive. Folic acid was the most commonly consumed healthy food, followed by iron and calcium.

CONCLUSIONS

This study clarified the real-world situation regarding healthy foods for women seeking pregnancy in Japan. The information necessary for pregnant women to select safe healthy foods was clarified, which may lead to the establishment of risk-communication measures to ensure safety.

Obesity, Dietary Patterns, and Hormonal Balance Modulation: Gender-Specific Impacts

Understanding the intricate relationship between nutrition, hormonal balance, and gender-specific factors is crucial for developing targeted interventions to mitigate obesity-related endocrine disruptions and improve metabolic health. This narrative review examines the impact of various dietary patterns on hormonal regulation in both men and women, focusing on their effects on hormonal balance and metabolic health in the context of obesity. Calorie restriction, the Western diet, high-fat diets, low-CHO diets, plant-based diets, and the Mediterranean diet are analyzed in relation to their influence on obesity-related endocrine disruptions and metabolic health. Future research directions include investigating the specific mechanisms underlying dietary influences on hormonal regulation, addressing the gender-specific metabolic differences and body fat distribution, and exploring the dietary needs of individuals undergoing gender transition. Personalized dietary interventions tailored to individual metabolic and hormonal profiles are essential for optimizing health outcomes across the gender spectrum. By integrating gender-specific considerations into dietary recommendations, healthcare professionals can better support individuals in achieving optimal metabolic health and hormonal balance.

Micronutrient Antioxidants for Men (Menevit®) Improve Sperm Function by Reducing Oxidative Stress, Resulting in Improved Assisted Reproductive Technology Outcomes

Oxidative stress (OS) affects men's health and impairs spermatogenesis. Micronutrient antioxidants are available for male infertility as complemental support; however, their efficacy remains debatable. This study aimed to investigate whether antioxidants can help to reduce sperm OS and improve semen analysis and quality. We included 171 male partners of couples planning to undergo assisted reproductive technology (ART). Male partners, aged 29-41 years, of couples intending to conceive were self-selected to take daily antioxidants (n = 84) containing folic acid and zinc, or not to take antioxidants (n = 52) for 6 months. We analyzed the alterations in serum oxidant levels, sperm parameters, OS, and deoxyribonucleic acid fragmentation after 3 and 6 months. Additionally, implantation, clinical pregnancy, and miscarriage rates after vitrified-warmed embryo transfer were compared between those taking antioxidants and those not taking them after 6 months. In men with high static oxidation-reduction potential (sORP), we observed a significant improvement in sperm concentration and sORP. The high-quality blastocyst rate tended to increase, and implantation and clinical pregnancy rates also significantly increased after 6 months of intervention. The micronutrient antioxidants could improve sperm function by reducing OS and improving ART outcomes. Therefore, micronutrient antioxidants may be a viable treatment option for male infertility.

The Uncontrollable Mortality Risk Hypothesis: Theoretical foundations and implications for public health

The 'Uncontrollable Mortality Risk Hypothesis' employs a behavioural ecological model of human health behaviours to explain the presence of social gradients in health. It states that those who are more likely to die due to factors beyond their control should be less motivated to invest in preventative health behaviours. We outline the theoretical assumptions of the hypothesis and stress the importance of incorporating evolutionary perspectives into public health. We explain how measuring perceived uncontrollable mortality risk can contribute towards understanding socioeconomic disparities in preventative health behaviours. We emphasize the importance of addressing structural inequalities in risk exposure, and argue that public health interventions should consider the relationship between overall levels of mortality risk and health behaviours across domains. We suggest that measuring perceptions of uncontrollable mortality risk can capture the unanticipated health benefits of structural risk interventions, as well as help to assess the appropriateness of different intervention approaches.

Association between dietary inflammation index and female infertility from National Health and Nutrition Examination Survey: 2013-2018

Objective

To investigate the relationship between dietary inflammatory index (DII) scores and infertility in US adults aged 18 to 45.

Methods

Data were gathered from the 2013-2018 National Health and Nutrition Examination Survey (NHANES). In total, 3496 women were included in the study. To examine the relationship between DII, EDII and infertility, a weighted multivariable logistic regression analysis using continuous factors or categorical variables grouped by quartiles was conducted. Using subgroup analysis stratified based on DII and infertility features, the association between DII and infertility has been further studied. In order to determine whether there was a nonlinear relationship between DII and infertility, restricted cubic spline (RCS) analysis was carried out.

Results

For statistical analysis, a total of 3496 individuals - 367 patients with infertility and 3129 persons without infertility - were included. A multivariable logistic regression study revealed a positive relationship between DII and infertility. A significant difference in subgroup analysis was shown in age group and race, although RCS analysis demonstrated nonlinear relationship between the DII and infertility.

Conclusion

For participants aged 18-45 years, higher DII scores were positively correlated with infertility. In addition, anti-inflammatory diets might improve infertility outcomes.

High Dietary Inflammatory Index increases the risk of female infertility: An analysis of NHANES 2013-2018

Diet-related inflammation, which can be evaluated using the dietary inflammatory index (DII), is increasingly related to female infertility. However, studies on the association between DII and infertility are limited. In this study, we aim to explore the association between DII and infertility and its dose-effect relationship among women aged 20 to 45 years through a cross-sectional analysis of the National Health and Nutrition Examination Survey 2013-2018. A total of 2613 women aged 20 to 45 years were included and analyzed. The DII was calculated using the first 24-hour dietary recall interview data and divided into quartiles. Weighted multivariable logistic regression and restricted cubic spline analysis were used to explore the relationship between DII and infertility. The odds ratio (OR) (95% confidence interval [CI]) for the association between DII and infertility was 1.06 (0.96-1.19) after multivariable adjustment. Compared with the first quartile (anti-inflammatory diet), the fourth quartile of DII (pro-inflammatory diet) was more strongly associated with an increased risk of infertility, with an OR of 1.61 (95% CI, 1.05-2.47). Restricted cubic splines showed a J-shaped nonlinear association between DII and infertility (P for nonlinear = .003), with a cutoff point of 2.45. When DII was higher than 2.45, the OR for infertility was 1.95 (95% CI, 1.49-2.54). Similar results were observed among the subgroup analyses. In conclusion, this study found high DII (pro-inflammatory diet) increases the risk of female infertility. DII had a J-shaped nonlinear relationship with female infertility, whose cut point is 2.45. Controlling the intake of pro-inflammatory food may be beneficial for female infertility.

What is driving the global decline of human fertility? Need for a multidisciplinary approach to the underlying mechanisms

An intense period of human population expansion over the past 250 years is about to cease. Total fertility rates are falling dramatically all over the world such that highly industrialized nations, including China and the tiger economies of SE Asia, will see their populations decline significantly in the coming decades. The socioeconomic, geopolitical and environmental ramifications of this change are considerable and invite a multidisciplinary consideration of the underlying mechanisms. In the short-term, socioeconomic factors, particularly urbanization and delayed childbearing are powerful drivers of reduced fertility. In parallel, lifestyle factors such as obesity and the presence of numerous reproductive toxicants in the environment, including air-borne pollutants, nanoplastics and electromagnetic radiation, are seriously compromising reproductive health. In the longer term, it is hypothesized that the reduction in family size that accompanies the demographic transition will decrease selection pressure on high fertility genes leading to a progressive loss of human fecundity. Paradoxically, the uptake of assisted reproductive technologies at scale, may also contribute to such fecundity loss by encouraging the retention of poor fertility genotypes within the population. Since the decline in fertility rate that accompanies the demographic transition appears to be ubiquitous, the public health implications for our species are potentially devastating.

Examining the Role of Nutrition in Cancer Survivorship and Female Fertility: A Narrative Review

Female cancer survivors have a higher chance of experiencing infertility than females without a history of cancer diagnosis. This risk remains high despite advances in fertility treatments. There is a need to augment fertility treatments with cost-effective methods such as nutritional guidance to improve fertility chances. The aim of this review article is to connect the current literature on cancer survivorship nutrition and fertility nutrition, focusing on the importance of integrating nutritional guidance into fertility counseling, assessment, and treatment for female cancer survivors. Consuming a healthful diet comprising whole grains, soy, fruits, vegetables, seafood, and unsaturated fats has improved both female fertility and cancer survivorship. Similarly, maintaining a healthy body weight also improves female fertility and cancer survivorship. Therefore, dietary interventions to support female cancer survivors with fertility challenges are of immense importance. The period of follow-up fertility counseling and assessment after cancer treatment may provide a unique opportunity for implementing nutritional guidance for female cancer survivors. Dietary interventions are a promising strategy to improve pregnancy chances and overall quality of life among female cancer survivors; thus, researchers should investigate perceptions regarding fertility, barriers, and challenges to changing nutrition-related behaviors, and preferences for nutritional guidance to support fertility treatments in this population.

Minerals and the Menstrual Cycle: Impacts on Ovulation and Endometrial Health

The role of minerals in female fertility, particularly in relation to the menstrual cycle, presents a complex area of study that underscores the interplay between nutrition and reproductive health. This narrative review aims to elucidate the impacts of minerals on key aspects of the reproductive system: hormonal regulation, ovarian function and ovulation, endometrial health, and oxidative stress. Despite the attention given to specific micronutrients in relation to reproductive disorders, there is a noticeable absence of a comprehensive review focusing on the impact of minerals throughout the menstrual cycle on female fertility. This narrative review aims to address this gap by examining the influence of minerals on reproductive health. Each mineral's contribution is explored in detail to provide a clearer picture of its importance in supporting female fertility. This comprehensive analysis not only enhances our knowledge of reproductive health but also offers clinicians valuable insights into potential therapeutic strategies and the recommended intake of minerals to promote female reproductive well-being, considering the menstrual cycle. This review stands as the first to offer such a detailed examination of minerals in the context of the menstrual cycle, aiming to elevate the understanding of their critical role in female fertility and reproductive health.

Influence of nutritional supplements on antibody levels in pregnant women vaccinated with inactivated SARS-CoV-2 vaccines

BACKGROUND

Because of the significantly higher demand for nutrients during pregnancy, pregnant women are more likely to have nutrient deficiencies, which may adversely affect maternal and fetal health. The influence of nutritional supplements on the immune effects of inactivated SARS-CoV-2 vaccines during pregnancy is not clear.

METHODS

In a multicenter cross-sectional study, we enrolled 873 pregnant women aged 18-45 y in Guangdong, China. The general demographic characteristics of pregnant women and their use of nutritional supplements were investigated, and the serum antibody levels induced by inactivated SARS-CoV-2 vaccines were measured. A logistic regression model was used to analyze the association between nutritional supplements and SARS-CoV-2 antibody levels.

RESULTS

Of the 873 pregnant women enrolled, 825 (94.5%) took folic acid during pregnancy, 165 (18.9%) took iron supplements, and 197 (22.6%) took DHA. All pregnant women received at least one dose of inactivated SARS-CoV-2 vaccine, and the positive rates of serum SARS-CoV-2 neutralizing antibodies (NAbs) and immunoglobulin G (IgG) antibodies were 44.7% and 46.4%, respectively. After adjustment for confounding factors, whether pregnant women took folic acid, iron supplements, or DHA did not influence NAb positivity or IgG positivity (P > 0.05). Compared with pregnant women who did not take folic acid, the odds ratios (ORs) for the presence of SARS-CoV-2 NAb and IgG antibody in pregnant women who took folic acid were 0.67 (P = 0.255; 95% CI, 0.34-1.32) and 1.24 (P = 0.547; 95% CI, 0.60-2.55), respectively. Compared with pregnant women who did not take iron supplements, the ORs for the presence of NAb and IgG antibody in pregnant women who took iron supplements were 1.16(P = 0.465; 95% CI, 0.77-1.76) and 0.98 (P = 0.931; 95% CI, 0.64-1.49), respectively. Similarly, the ORs for NAb and IgG antibody were 0.71 (P = 0.085; 95% CI, 0.49-1.04) and 0.95 (P = 0.801; 95% CI, 0.65-1.38) in pregnant women who took DHA compared with those who did not.

CONCLUSIONS

Nutritional supplementation with folic acid, iron, or DHA during pregnancy was not associated with antibody levels in pregnant women who received inactivated SARS-CoV-2 vaccines.

Relationship between dietary glycemic index and glycemic load and sperm-quality parameters in Iranian men: a cross-sectional study

BACKGROUND

Infertility is a major clinical problem with psychological, financial and medical costs. Male infertility has recently been linked to 50% of childless couples. It is worth mentioning that diet and its components can be manipulated and applied in counseling meetings of infertile men as a modifiable factor. The goal of this study was to determine the correlation of dietary glycemic index (GI) and glycemic load (GL) with sperm-quality parameters in Iranian men.

MATERIALS AND METHODS

In this cross-sectional study which was carried from Aug to Nov 2023, after excluding smokers, 322 men who were attending the IVF clinic of Ayatollah Mousavi Hospital for seminal analysis were enrolled. Dietary intake was completed by an expert dietitian through face-to-face interviews with a validated 168-item food frequency questionnaire (FFQ). In the present study, sperm-quality parameters, including motility, concentration, normal morphology, vitality, DNA fragmentation index (DFI), and chromatin maturation of sperm, were analyzed. The relationship between dietary GI and CL and these parameters was assessed.

RESULTS

Adjusting for the baseline variables, dietary GI and GL showed positive and negative associations with sperm progressive motility, respectively (p = 0.01 and p < 0.001). Higher dietary GI was associated with lower (p = 0.03); however, a higher dietary GL was associated with higher immotile sperm (p < 0.001). A higher dietary GI was associated with a 77% higher sperm count (p = 0.003). In contrast, higher dietary GL was associated with a lower count (p < 0.001). Higher dietary GI and GL were associated with higher and lower percentages of sperm with normal morphology by 70% and 40%, respectively (p < 0.001 in both). A higher dietary GL was associated with an increase in sperm vitality and DFI of 33% and 53%, respectively (p < 0.001). Higher dietary GI showed a significant negative effect on sperm DFI (p = 0.009). Dietary GI and GL showed significant positive and negative effects on SCMA, respectively (p = 0.002 and p < 0.001).

CONCLUSION

A diet with a higher GI showed beneficial effects on more parameters of sperm; however, higher dietary GL showed deleterious effects, except sperm vitality and SCMA. More studies are needed to obtain a concise result.

Food, nutrition, and fertility: from soil to fork

Food and nutrition-related factors, including foods and nutrients consumed, dietary patterns, use of dietary supplements, adiposity, and exposure to food-related environmental contaminants, have the potential to impact semen quality and male and female fertility; obstetric, fetal, and birth outcomes; and the health of future generations, but gaps in evidence remain. On 9 November 2022, Tufts University's Friedman School of Nutrition Science and Policy and the school's Food and Nutrition Innovation Institute hosted a 1-d meeting to explore the evidence and evidence gaps regarding the relationships between food, nutrition, and fertility. Topics addressed included male fertility, female fertility and gestation, and intergenerational effects. This meeting report summarizes the presentations and deliberations from the meeting. Regarding male fertility, a positive association exists with a healthy dietary pattern, with high-quality evidence for semen quality and lower quality evidence for clinical outcomes. Folic acid and zinc supplementation have been found to not impact male fertility. In females, body weight status and other nutrition-related factors are linked to nearly half of all ovulation disorders, a leading cause of female infertility. Females with obesity have worse fertility treatment, pregnancy-related, and birth outcomes. Environmental contaminants found in food, water, or its packaging, including lead, perfluorinated alkyl substances, phthalates, and phenols, adversely impact female reproductive outcomes. Epigenetic research has found that maternal and paternal dietary-related factors can impact outcomes for future generations. Priority evidence gaps identified by meeting participants relate to the effects of nutrition and dietary patterns on fertility, gaps in communication regarding fertility optimization through changes in nutritional and environmental exposures, and interventions impacting germ cell mechanisms through dietary effects. Participants developed research proposals to address the priority evidence gaps. The workshop findings serve as a foundation for future prioritization of scientific research to address evidence gaps related to food, nutrition, and fertility.

Association between dietary inflammatory index and self-reported female infertility from the National Health and Nutrition Examination Survey 2013-2020

BACKGROUND

To explore the association between the diet inflammatory index (DII) and infertility.

METHODS

Multivariable logistic regression was performed to investigate the relationship between infertility and DII, and restricted cubic spline (RCS) was utilised to test for nonlinear relationships in this cross-sectional study. Data of this study were collected from the 2013 to 2020 National Health and Nutrition Examination Survey (NHANES) database. Considering women's child-bearing age, we enrolled a total of 2066 women aged 20-45 years in this study.

RESULTS

After all covariates were adjusted, a positive association was found between DII score and odds of infertility by multivariable logistic regression (odds ratio [OR] = 1.19, 95% confidence interval [CI] 1.03, 1.38; p = 0.027). Compared with participants with DII scores in the lowest quartile, those with DII scores in the highest quartile had significantly higher odds of infertility (OR = 2.42, 95% CI 1.09, 5.34; p = 0.034). The RCSs model suggested a linear relationship between DII and infertility (p for nonlinear = 0.1827).

CONCLUSIONS

A positive association between a pro-inflammatory diet and self-reported infertility was detected. Our study extends the application of the DII scoring system to infertility prevention.

Metabolic hormones are integral regulators of female reproductive health and function

The female reproductive system is strongly influenced by nutrition and energy balance. It is well known that food restriction or energy depletion can induce suppression of reproductive processes, while overnutrition is associated with reproductive dysfunction. However, the intricate mechanisms through which nutritional inputs and metabolic health are integrated into the coordination of reproduction are still being defined. In this review, we describe evidence for essential contributions by hormones that are responsive to food intake or fuel stores. Key metabolic hormones-including insulin, the incretins (glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1), growth hormone, ghrelin, leptin, and adiponectin-signal throughout the hypothalamic-pituitary-gonadal axis to support or suppress reproduction. We synthesize current knowledge on how these multifaceted hormones interact with the brain, pituitary, and ovaries to regulate functioning of the female reproductive system, incorporating in vitro and in vivo data from animal models and humans. Metabolic hormones are involved in orchestrating reproductive processes in healthy states, but some also play a significant role in the pathophysiology or treatment strategies of female reproductive disorders. Further understanding of the complex interrelationships between metabolic health and female reproductive function has important implications for improving women's health overall.

Associations of Nutrients and Dietary Preferences with Recurrent Pregnancy Loss and Infertility

This review examines associations of nutrients and dietary preferences with recurrent pregnancy loss (RPL), miscarriage, and infertility. Research articles, reviews, and meta-analyses of RPL and infertility that focused on nutrition, meals, and lifestyle were reviewed, and associations of nutrients and dietary preferences with pregnancy are discussed in relation to recent research findings. Studies related to RPL were given the highest priority, followed by those dealing with miscarriage and infertility. Multivitamin supplements-even when lacking folic acid or vitamin A-reduced total fetal loss. High-dose folic acid supplementation before conception reduced the risk of miscarriage and stillbirth. A meta-analysis revealed a strong association of vitamin D deficiency/insufficiency with miscarriage. Another meta-analysis revealed that seafood and dairy products reduced the risk of miscarriage, whereas a caffeine intake of 300 mg/day or more was associated with miscarriage. A balanced diet that included nutrients with antioxidant properties helped prevent miscarriage, whereas a diet that included processed foods and nutrients with proinflammatory effects increased the risk of miscarriage. Associations of nutrients with RPL warrant further research.