Alcohol and dietary folate intake and the risk of breast cancer: a case-control study in Japan

Systematic Review and Meta-Analysis of Lifestyle and Reproductive Factors Associated with Risk of Breast Cancer in Asian Women

BACKGROUND

Assessing breast cancer risks from lifestyle and reproductive factors is critical for developing population-specific risk prediction tools. However, limited studies have evaluated these risks in recent Asian birth cohorts.

METHODS

We systematically reviewed articles published from January 2010 to December 2023, examining breast cancer risk factors in Asian women. Data were described narratively, estimates pooled, and prevalence and attributable proportions compared across Asian populations.

RESULTS

Of the 128 studies reviewed, 103 reported adjusted effect sizes for meta-analysis. Lifestyle and reproductive factors were predictive of breast cancer risk in Asian women, with varying impacts on premenopausal and postmenopausal women. Relative risks were similar within Asian populations and in comparison to European populations, except for menarche, menopause, and hormone receptor therapy. However, risk factor distributions differed across populations. While alcohol intake (21%) and oral contraceptive use (20%) emerged as the most attributable modifiable risk factors in Europeans, passive smoking (24%) and higher BMI (17%, ≥24 kg/m2 among postmenopausal women) were predominant in Asians.

CONCLUSIONS

Our study shows that while the effects of lifestyle and reproductive breast cancer risk factors are largely similar across different populations, their distributions vary.

IMPACT

Our analysis underscores the importance of considering population-specific risk factor distributions when developing risk prediction tools for Asian populations.

Red blood cell folate level is associated with periodontitis in American adults: results from the NHANES 2009-2014

BACKGROUND

Red blood cell (RBC) folate is an indicator of long-term folate nutrition. Whether there is an association between RBC folate and periodontitis is unclear. This study aimed to use the NHANES database to determine whether RBC folate is associated with moderate/severe periodontitis.

METHODS

A cross-sectional analysis of 10,151 participants in the NHANES database from 2009 to 2014 was performed. Multivariate logistic regression was used to analyze the independent relationship between RBC folate and moderate/severe periodontitis. The generalized additive model (GAM), restricted cubic splines (RCS), smooth curve fitting, and threshold effect analysis were used to explore the dose-response relationship and the potential nonlinear relationship between RBC folate and periodontitis. Finally, subgroup analysis and interaction tests were performed to determine the effect of covariates on the relationship between RBC folate and moderate/severe periodontitis.

RESULTS

After adjusting for all confounders, there was a negative association between RBC folate concentration and moderate/severe periodontitis. The lowest fraction Q1 (< 360 ng/mL) of RBC folate concentration was used as the reference group, multivariable-adjusted ORs and 95% CIs of the second (360-463 ng/mL), third (464-569 ng/mL), fourth (570-732 ng/mL), and the highest quintile (> 733 ng/mL) categories were 0.88 (0.77, 1.01), 0.83 (0.72, 0.96), 0.77 (0.67, 0.90), 0.65 (0.56, 0.77) respectively. Additionally, a threshold nonlinear association was found between RBC folate (ng/mL) log2 transformation and moderate/severe periodontitis.

CONCLUSION

This cross-sectional study revealed a negative relationship between RBC folate and moderate/severe periodontitis within a certain threshold range. Dentists and policymakers should pay closer attention to oral hygiene and health care for people with low or high RBC folate levels. Further causal and longitudinal research mechanisms are needed to validate our findings.

Temporal patterns of breast cancer incidence, mortality, disability-adjusted life years and risk factors in 12 South American Countries, 1990-2019: an examination using estimates from the global burden of disease 2019 study

BACKGROUND AND AIM

Breast cancer (BC) is one of the leading causes of cancer deaths in females in South America. This study aims to examine the BC burden in 12 South American countries between 1990 and 2019.

DATA AND METHODS

The estimates of BC burden and risk factors were procured from the Global Burden of Disease 2019 study for the period 1990-2019. Development levels of countries were gauged using socio-demographic index (SDI). Decomposition analysis was employed to categorize the change in incidence between 1990 and 2019 into three factors: population growth, population aging and age-specific incidence rate. Estimated annual percent changes were calculated for each country and bivariate association between country-level age-standardized rates and SDI was examined using pooled regression.

RESULTS

The age-standardized rates of breast cancer were the highest in Uruguay [incidence: 72.65 per 100,000 (55.79-92.57); mortality: 29.97 per 100,000 (27.54-32.27); disability-adjusted life years (DALYs: 810.49 per 100,000 (746.22-884.55)] and lowest in Peru [incidence: 27.63 per 100,000 (20.44-36.85); mortality: 10.79 per 100,000 (8.14-14.11); DALYs: 318.27 per 100,000 (234.47-421.16)]. Mortality-to-incidence ratio (MIR) across countries varied from 0.30 in Colombia to 0.55 in Bolivia in 2019. SDI had a positive and strong association with age-standardized incidence rate [Formula: see text] and weaker positive association with age-standardized mortality rate [Formula: see text] and age-standardized DALYs rate [Formula: see text]. Most countries experienced more than 70% increase in incident cases owing to population aging and age-specific incidence rates. Alcohol Use, diet high in red meat and smoking contributed the maximum DALYs in most countries in 2019 whereas DALYs due to high body-mass index and high fasting plasma glucose increased most substantially between 1990 and 2019.

CONCLUSION

With increasing incidence, high MIR and rising BC burden due to modifiable risk factors, several public health interventions are required in South America focusing on prevention, BC awareness among general public, cost-effective early detection and treatments that suit the socio-economic setup of South American countries.

Alcohol consumption and breast cancer risk in Japan: A pooled analysis of eight population-based cohort studies

Although alcohol consumption is reported to increase the incidence of breast cancer in European studies, evidence for an association between alcohol and breast cancer in Asian populations is insufficient. We conducted a pooled analysis of eight large-scale population-based prospective cohort studies in Japan to evaluate the association between alcohol (both frequency and amount) and breast cancer risk with categorization by menopausal status at baseline and at diagnosis. Estimated hazard ratios (HR) and 95% confidence intervals were calculated in the individual cohorts and combined using random-effects models. Among 158 164 subjects with 2 369 252 person-years of follow-up, 2208 breast cancer cases were newly diagnosed. Alcohol consumption had a significant association with a higher risk of breast cancer in both women who were premenopausal at baseline (regular drinker compared to nondrinker: HR 1.37, 1.04-1.81, ≥23 g/d compared to 0 g/d: HR 1.74, 1.25-2.43, P for trend per frequency category: P = .017) and those who were premenopausal at diagnosis (≥23 g/d compared to 0 g/d: HR 1.89, 1.04-3.43, P for trend per frequency category: P = .032). In contrast, no significant association was seen in women who were postmenopausal at baseline or at diagnosis, despite a substantial number of subjects and long follow-up period. Our results revealed that frequent and high alcohol consumption are both risk factors for Asian premenopausal breast cancer, similarly to previous studies in Western countries. The lack of a clear association in postmenopausal women in our study warrants larger investigation in Asia.

Association of folate intake and plasma folate level with the risk of breast cancer: a dose-response meta-analysis of observational studies

Epidemiological studies showing the correlation between folate and the breast cancer risk have revealed inconsistent results. Hence, we conducted a dose-response meta-analysis of observational studies to obtain more reliable conclusions. We searched PubMed and Embase for studies published before April 2019 and identified 39 studies on folate intake and 12 studies on plasma folate level. The combined odds ratios (ORs) and 95% confidence intervals (CIs) were extracted to estimate the breast cancer risk. Folate intake was inversely correlated with the breast cancer risk when the highest and lowest categories (OR = 0.85, 95% CI = 0.79-0.92) were compared, and the dose-response result showed that folate intake had a linear correlation with the breast cancer risk. Moreover, a higher folate intake correlated with a lower breast cancer risk in premenopausal women (OR = 0.80, 95% CI = 0.66-0.97), but not in postmenopausal women (OR = 0.94, 95% CI = 0.83-1.06). However, plasma folate levels were not correlated with the breast cancer risk (OR = 0.98, 95% CI = 0.82-1.17). Folate intake was negatively correlated with the breast cancer risk; however, its practical clinical significance requires further study. Furthermore, additional folate supplements should be considered carefully.

The association of CASC16 variants with breast Cancer risk in a northwest Chinese female population

Purpose

Genetic variants play a critical role in the development of breast cancer. This investigation aimed to explore the association between CASC16 polymorphisms and breast cancer susceptibility.

Methods

We conducted a case-control study of 681 patients and 680 healthy individuals to investigate the correlation of five SNPs with breast cancer in a Northwest Chinese female population. Odds ratios (OR) and 95% confidence intervals (CIs) were used to assess the association.

Results

Our study found that rs4784227 and rs12922061 were significantly related to an increased susceptibility to breast cancer (OR 1.22, p = 0.022; OR 1.21, p = 0.026). While rs3803662 was a protective role in breast cancer risk (OR 0.69, p = 0.042). Stratified analyses indicated that rs4784227 and rs12922061 would increase breast cancer susceptibility at age >  50 years. Rs3803662 was a reduced factor of breast cancer risk by age ≤ 50 years. Rs4784227 was significantly increased risk of breast cancer in stage III/IV. The rs45544231 and rs3112612 had a protective effect on breast cancer with tumor size > 2 cm. Rs4784227 and rs12922061 could enhance breast cancer risk in lymph node metastasis positive individuals. CASC16 rs12922061 and rs4784227 polymorphisms correlated with an increased risk of breast cancer in BMI >  24 kg/m². Haplotype analyses revealed that G_rs45544231 T_rs12922061 A_rs3112612 and G_rs45544231 C_rs12922061 A_rs3112612 haplotypes decreased breast cancer risk.

Conclusion

Our study revealed that CASC16 genetic variants were significantly related to breast cancer susceptibility, which might give scientific evidence for exploring the molecular mechanism of breast cancer.

Nutritional assessment of female patients newly diagnosed with breast cancer in a northern region of Spain

Introduction

Background: evidence from research suggests that the development of cancer disease is associated with environmental factors. There are few studies evaluating nutritional status in women suffering from cancer in Spain. Objectives: this study aimed to assess the nutritional status in breast cancer female patients at diagnosis in a northern region of Spain (Asturias), where breast cancer rates are particularly high when compared to the rest of Spain. Material and methods: a cross-sectional study was conducted in a sample of 76 newly diagnosed female cancer patients. Lifestyle factors, anthropometry, biochemical, and dietary intake data were collected immediately after diagnosis and prior to the initiation of the prescribed treatment. Results: a high percentage of these women diagnosed with cancer were sedentary (59.2%). Their average body mass index (BMI) was 27.3 ± 5.5 kg/m2. They also showed a high percentage of body fat, 38.3%, as well as a large waist circumference of 92.2 cm. Patients reported a low intake of fruits, vegetables, legumes, and nuts, and a high intake of red meat, meat products, and sweet foodstuffs as compared to the Spanish dietary guidelines (p < 0.01). Conclusion: the results showed a low intake of folate, calcium, and vitamin D, which is particularly relevant in women. In conclusion, these breast cancer patients showed overweight and high sedentarism levels, and reported unbalanced dietary patterns at the time of diagnosis.

Wine consumption and colorectal cancer risk: a meta-analysis of observational studies

There were inconsistent results with respect to the correlation between consumption of wine and the development of colorectal cancer (CRC). We carried out a meta-analysis to investigate this issue. We included observational studies on the aforementioned relationship according to a literature search of Embase and Pubmed from inception till 28 February 2017. The summary relative risk (SRR) and 95% confidence intervals (CI) were calculated using a random-effects model. A total of eight case-control and nine cohort studies were identified, involving 12 110 CRC cases. The study showed that wine drinking was not associated with any greater risk for CRC (SRR=0.99, 95% CI: 0.89-1.10; Pheterogeneity<0.001) compared with nondrinkers. The subgroup analyses indicated that null associations were observed in men and women for colon and rectal cancer. Neither light to moderate (<2 drinks/day; SRR=0.93, 95% CI: 0.80-1.08, I= 69.2%) nor heavy (≥2 drinks/day; SRR=1.00, 95% CI: 0.86-1.16, I= 39.9%) consumption of wine was associated statistically with CRC risk. This meta-analysis suggests that any wine consumption was not associated with the risk of CRC. Null associations were shown in men and women for colon and rectal cancer.

Epidemiology of Moderate Alcohol Consumption and Breast Cancer: Association or Causation?

Epidemiological studies have been used to show associations between modifiable lifestyle habits and the incidence of breast cancer. Among such factors, a history of alcohol use has been reported in multiple studies and meta-analyses over the past decades. However, associative epidemiological studies that were interpreted as evidence that even moderate alcohol consumption increases breast cancer incidence have been controversial. In this review, we consider the literature on the relationship between moderate or heavy alcohol use, both in possible biological mechanisms and in variations in susceptibility due to genetic or epigenetic factors. We argue that there is a need to incorporate additional approaches to move beyond the associations that are reported in traditional epidemiological analyses and incorporate information on molecular pathologic signatures as a requirement to posit causal inferences. In particular, we point to the efforts of the transdisciplinary field of molecular pathological epidemiology (MPE) to evaluate possible causal relationships, if any, of alcohol consumption and breast cancer. A wider application of the principles of MPE to this field would constitute a giant step that could enhance our understanding of breast cancer and multiple modifiable risk factors, a step that would be particularly suited to the era of "personalized medicine".

ALDH1L1 and ALDH1L2 Folate Regulatory Enzymes in Cancer

Epidemiological studies implicate excess ethanol ingestion as a risk factor for several cancers and support the concept of a synergistic effect of chronic alcohol consumption and folate deficiency on carcinogenesis. Alcohol consumption affects folate-related genes and enzymes including two major folate-metabolizing enzymes, ALDH1L1 and ALDH1L2. ALDH1L1 (cytosolic 10-formyltetrahydrofolate dehydrogenase) is a regulatory enzyme in folate metabolism that controls the overall flux of one-carbon groups in folate-dependent biosynthetic pathways. It is strongly and ubiquitously down-regulated in malignant tumors via promoter methylation, and recent studies underscored this enzyme as a candidate tumor suppressor and potential marker of aggressive cancers. A related enzyme, ALDH1L2, is the mitochondrial homolog of ALDH1L1 encoded by a separate gene. In contrast to its cytosolic counterpart, ALDH1L2 is expressed in malignant tumors and cancer cell lines and was implicated in metastasis regulation. This review discusses the link between folate and cancer, modifying effects of alcohol consumption on folate-associated carcinogenesis, and putative roles of ALDH1L1 and ALDH1L2 in this process.

Alcoholic Beverage Consumption and Chronic Diseases

Epidemiological and experimental studies have consistently linked alcoholic beverage consumption with the development of several chronic disorders, such as cancer, cardiovascular diseases, diabetes mellitus and obesity. The impact of drinking is usually dose-dependent, and light to moderate drinking tends to lower risks of certain diseases, while heavy drinking tends to increase the risks. Besides, other factors such as drinking frequency, genetic susceptibility, smoking, diet, and hormone status can modify the association. The amount of ethanol in alcoholic beverages is the determining factor in most cases, and beverage types could also make an influence. This review summarizes recent studies on alcoholic beverage consumption and several chronic diseases, trying to assess the effects of different drinking patterns, beverage types, interaction with other risk factors, and provide mechanistic explanations.

Diet and risk of breast cancer

Diet may play a role in both promoting and inhibiting human breast cancer development. In this review, nutritional risk factors such as consumption of dietary fat, meat, fiber, and alcohol, and intake of phytoestrogen, vitamin D, iron, and folate associated with breast cancer are reviewed. These nutritional factors have a variety of associations with breast cancer risk. Type of fat consumed has different effects on risk of breast cancer: consumption of meat is associated with heterocyclic amine (HCA) exposure; different types of plant fiber have various effects on breast cancer risk; alcohol consumption may increase the risk of breast cancer by producing acetaldehyde and reactive oxygen species (ROS); intake of phytoestrogen may reduce risk of breast cancer through genomic and non-genomic action; vitamin D can reduce the risk of breast cancer by inhibiting the process of cancer invasion and metastasis; intake of dietary iron may lead to oxidative stress, DNA damage, and lipid peroxidation; and lower intake of folate may be linked to a higher risk of breast cancer.

A pilot genome-wide association study of breast cancer susceptibility loci in Indonesia

Genome-wide association studies (GWASs) of the entire genome provide a systematic approach for revealing novel genetic susceptibility loci for breast cancer. However, genetic association studies have hitherto been primarily conducted in women of European ancestry. Therefofre we here performed a pilot GWAS with a single nucleotide polymorphism (SNP) array 5.0 platform from Affymetrix® that contains 443,813 SNPs to search for new genetic risk factors in 89 breast cancer cases and 46 healthy women of Indonesian ancestry. The case-control association of the GWAS finding set was evaluated using PLINK. The strengths of allelic and genotypic associations were assessed using logistic regression analysis and reported as odds ratios (ORs) and P values; P values less than 1.00x10(-8) and 5.00x10(-5) were required for significant association and suggestive association, respectively. After analyzing 292,887 SNPs, we recognized 11 chromosome loci that possessed suggestive associations with breast cancer risk. Of these, however, there were only four chromosome loci with identified genes: chromosome 2p.12 with the CTNNA2 gene [Odds ratio (OR)=1.20, 95% confidence interval (CI)=1.13-1.33, P=1.08x10(-7)]; chromosome 18p11.2 with the SOGA2 gene (OR=1.32, 95%CI=1.17-1.44, P=6.88x10(-6)); chromosome 5q14.1 with the SSBP2 gene (OR=1.22, 95%CI=1.11-1.34, P=4.00x10(-5)); and chromosome 9q31.1 with the TEX10 gene (OR=1.24, 95%CI=1.12-1.35, P=4.68x10(-5)). This study identified 11 chromosome loci which exhibited suggestive associations with the risk of breast cancer among Indonesian women.

The Malaysian Breast Cancer Survivorship Cohort (MyBCC): a study protocol

INTRODUCTION

Over recent decades, the burden of breast cancer has been increasing at an alarming rate in Asia. Prognostic research findings from Western countries may not readily be adapted to Asia, as the outcome of breast cancer depends on a multitude of factors ranging from genetic, clinical and histological predictors, to lifestyle and social predictors. The primary aim of this study is to determine the impact of lifestyle (eg, nutrition, physical activity), mental and sociocultural condition, on the overall survival and quality of life (QoL) among multiethnic Malaysian women following diagnosis of breast cancer. This study aims to advance the evidence on prognostic factors of breast cancer within the Asian setting. The findings may guide management of patients with breast cancer not only during active treatment but also during the survivorship period.

METHODS

This hospital-based prospective cohort study will comprise patients with breast cancer (18 years and above), managed in the University Malaya Medical Centre (UMMC). We aim to recruit 1000 cancer survivors over a 6-year period. Data collection will occur at baseline (within 3 months of diagnosis), 6 months, and 1, 3 and 5 years following diagnosis. The primary outcomes are disease-free survival and overall survival, and secondary outcome is QoL. Factors measured are demographic and socioeconomic factors, lifestyle factors (eg, dietary intake, physical activity), anthropometry measurements (eg, height, weight, waist, hip circumference, body fat analysis), psychosocial aspects, and complementary and alternative medicine (CAM) usage.

ETHICS AND DISSEMINATION

This protocol was approved by the UMMC Ethical Committee in January 2012. All participants are required to provide written informed consent. The findings from our cohort study will be disseminated via scientific publication as well as presentation to stakeholders including the patients, clinicians, the public and policymakers, via appropriate avenues.

Alcohol and breast cancer: reconciling epidemiological and molecular data

Breast cancer is the most diagnosed cancer in women worldwide. Epidemiological studies have suggested a possible causative role of alcohol consumption as a risk factor for breast cancer. However, such conclusions should be interpreted with considerable caution for several reasons. While epidemiological studies can help identify the roots of health problems and disease incidence in a community, they are by necessity associative and cannot determine cause and effect relationships. In addition, all these studies rely on self-reporting to determine the amount and type of alcoholic beverage consumed, which introduces recall bias. This is documented in a recent study which stated that the apparent increased risk of cancer among light-moderate drinkers may be "substantially due to underreporting of intake." Another meta-analysis about alcohol and breast cancer declared "the modest size of the association and variation in results across studies leave the causal role of alcohol in question." Furthermore, breast cancer develops over decades; thus, correlations between alcohol consumption and breast cancer cannot be determined in epidemiological studies with windows of alcohol exposure that captures current or recent alcohol intake, after clinical diagnosis. Numerous risk factors are involved in breast carcinogenesis; some are genetic and beyond the control of a woman; others are influenced by lifestyle factors. Breast cancer is a heterogeneous and polygenic disease which is further influenced by epigenetic mechanisms that affect the transciptomes, proteomes and metabolomes, and ultimately breast cancer evolution. Environmental factors add another layer of complexity by their interactions with the susceptibility genes for breast cancer and metabolic diseases. The current state-of-knowledge about alcohol and breast cancer association is ambiguous and confusing to both a woman and her physician. Confronting the huge global breast cancer issue should be addressed by sound science. It is advised that women with or without a high risk for breast cancer should avoid overconsumption of alcohol and should consult with their physician about risk factors involved in breast cancer. Since studies associating moderate alcohol consumption and breast cancer are contradictory, a woman and her physician should weigh the risks and benefits of moderate alcohol consumption.

Association of dietary intake of folate, vitamin B6 and B12 and MTHFR genotype with breast cancer risk

AIM

We aimed to investigate the associations of dietary intake of folate, vitamin B6 and B12 and MTHFR genotype with breast cancer in a Chinese population.

METHODS

A matched case-control study was conducted, and 435 patients with newly diagnosed and histologically confirmed breast cancer and 435 controls were collected. The folate intake, vitamin B6 and vitamin B12 were calculated, and MTHFR C665T, C677T and A1298C were analyzed by PCR-RFLP.

RESULTS

We found vitamin B12 was likely to reduce the risk of breast cancer, and MTHFR 665TT was associated with increased risk of breast cancer. Folate intake, vitamin B12 intake and variants of MTHFR C677T and MTHFR A1298C demonstrated no association with risk of breast cancer. However, we found patients with low intake of vitamin B6 and MTHFR 665TT genotype had a higher risk of breast cancer (OR=1.87, 95% CI=1.29-2.77), the association being less pronounced among subjects with a moderate intake of vitamin B6 and MTHFR 665TT genotype (OR=1.58, 95% CI=1.03-2.49, P=0.03).

CONCLUSION

Our study indicated that the MTHFR C665T polymorphism and vitamin B6 are associated with risk of breast cancer, which indicated roles for nutrients in developing breast cancer.

Association of methylenetetrahydrofolate reductase and methionine synthase polymorphisms with breast cancer risk and interaction with folate, vitamin B6, and vitamin B 12 intakes

We assessed the association between dietary intake of folate and the MTHFR genotype with breast cancer in a Chinese population, with additional analysis of the interactions of gene polymorphisms and dietary intake of folate, vitamin B6, and vitamin B12. A case-control study was performed, and 535 patients with newly diagnosed breast cancer and 673 controls were enrolled into this study. The MTHFR 667TT genotype (odds ratio (OR) = 1.82, 95 % confidence interval (CI) = 1.24-2.97) and T allele (OR 0= 1.48, 95 % CI = 1.15-1.78) were correlated with a moderately significant increased risk of breast cancer when compared with the CC genotype. Individuals carrying the MTR 2756GG genotype (OR = 1.66, 95 % CI = 1.16-2.56) and G allele (OR = 1.42, 95 % CI = 1.26-1.81) had a higher risk of breast cancer when compared with subjects with the AA genotype. The MTHFR 667 T allele and MTR 2756 G allele were associated with a higher risk of breast cancer in individuals with low folate intake, vitamin B6, and vitamin B12, but the association disappeared among subjects with moderate and high intake of folate, vitamin B6, and vitamin B12. This case-control study found that the MTHFR C677T and MTR A2756G polymorphisms are associated with risk of breast cancer, and folate, vitamin B6, and vitamin B12 intakes influence these associations.

Lifestyle changes for prevention of breast cancer

Breast cancer is the second most common cause of death from cancer among women. Lifestyle changes are shown to be important in the prevention of breast cancer. Diet, physical activity, smoking, alcohol use, and vitamin and mineral use are key factors influencing the risk of breast cancer among women. Because these factors are related to each other, it is difficult to assess their individual roles in breast cancer. Some of these factors are alterable, meaning that women can decrease their risk for breast cancer by changing their behavior. Breast cancer is associated with a high rate of mortality and morbidity among women. Therefore, it is logical to try to find ways to decrease the risk of developing breast cancer. Lifestyle changes seem to be an easy, effective, and economical way to help prevention breast cancer. In women with a confirmed breast cancer diagnosis who are under radiotherapy treatment after undergoing a mastectomy, lifestyle changes are still very important. Some factors, such as smoking cessation and prevention of weight gain, may improve the long-term survival chances of these patients. Therefore, ways to increase women’s knowledge about the role of lifestyle changes in the prevention of breast cancer and in the survival of patients with diagnosed breast cancer should be considered and studied.

Folate intake and the risk of breast cancer: a systematic review and meta-analysis

There is conflicting epidemiological evidence on the role of folate and breast cancer risk. We conducted a systematic review and quantitative meta-analysis of folate intake and folate blood levels and the risk of breast cancer. Four electronic databases (Medline, PubMed, Embase, and Current Contents Connect) were searched to April 11, 2014, with no language restrictions for observational studies that measured folate intake or blood levels and the risk of breast cancer. The meta-analysis of dietary folate intake comprising 36 studies with 34,602 cases, and a total sample size of 608,265 showed a decreased risk of breast cancer, with an odds ratio (OR) of 0.84 [95 % confidence interval (CI) 0.77-0.91]. When stratified by menopausal status and by study design, none of the meta-analyses of prospective studies showed any statistically significant decrease in the risk of breast cancer. The meta-analysis of total folate showed no statistically significant association with breast cancer OR of 0.98 (95 % CI 0.91-1.07). There was no significant association between either dietary or total folate intake and breast cancer when stratified by hormonal receptor status. The meta-analysis of blood folate levels found no significant association with the risk of breast cancer, with an OR of 0.86 (95 % CI 0.60-1.25). Breast cancer does not appear to be associated with folate intake, and this did not vary by menopausal status or hormonal receptor status. Folate blood levels also do not appear to be associated with breast cancer risk.

Higher dietary folate intake reduces the breast cancer risk: a systematic review and meta-analysis

Background:

Many epidemiological studies have investigated the association between folate intake, circulating folate level and risk of breast cancer; however, the findings were inconsistent between the studies.

Methods:

We searched the PubMed and MEDLINE databases updated to January, 2014 and performed the systematic review and meta-analysis of the published epidemiological studies to assess the associations between folate intake level, circulating folate level and the overall risk of breast cancer.

Results:

In all, 16 eligible prospective studies with a total of 744 068 participants and 26 205 breast cancer patients and 26 case–control studies with a total of 16 826 cases and 21 820 controls that have evaluated the association between folate intake and breast cancer risk were identified. Pooled analysis of the prospective studies and case–control studies suggested a potential nonlinearity relationship for dietary folate intake and breast cancer risk. Prospective studies indicated a U-shaped relationship for the dietary folate intake and breast cancer risk. Women with daily dietary folate intake between 153 and 400 μg showed a significant reduced breast cancer risk compared with those <153 μg, but not for those >400 μg. The case–control studies also suggested a significantly negative correlation between the dietary folate intake level and the breast cancer risk. Increased dietary folate intake reduced breast cancer risk for women with higher alcohol intake level, but not for those with lower alcohol intake. No significant association between circulating folate level and breast cancer risk was found when the results of 8 identified studies with 5924 participants were pooled.

Conclusions:

Our studies suggested that folate may have preventive effects against breast cancer risk, especially for those with higher alcohol consumption level; however, the dose and timing are critical and more studies are warranted to further elucidate the questions.

Genome-wide association study of breast cancer in the Japanese population

Breast cancer is the most common malignancy among women in worldwide including Japan. Several studies have identified common genetic variants to be associated with the risk of breast cancer. Due to the complex linkage disequilibrium structure and various environmental exposures in different populations, it is essential to identify variants associated with breast cancer in each population, which subsequently facilitate the better understanding of mammary carcinogenesis. In this study, we conducted a genome-wide association study (GWAS) as well as whole-genome imputation with 2,642 cases and 2,099 unaffected female controls. We further examined 13 suggestive loci (P<1.0×10⁻⁵) using an independent sample set of 2,885 cases and 3,395 controls and successfully validated two previously-reported loci, rs2981578 (combined P-value of 1.31×10⁻¹², OR = 1.23; 95% CI = 1.16–.30) on chromosome 10q26 (FGFR2), rs3803662 (combined P-value of 2.79×10⁻¹¹, OR = 1.21; 95% CI = 1.15–.28) and rs12922061 (combined P-value of 3.97×10⁻¹⁰, OR = 1.23; 95% CI = 1.15–.31) on chromosome 16q12 (TOX3-LOC643714). Weighted genetic risk score on the basis of three significantly associated variants and two previously reported breast cancer associated loci in East Asian population revealed that individuals who carry the most risk alleles in category 5 have 2.2 times higher risk of developing breast cancer in the Japanese population than those who carry the least risk alleles in reference category 1. Although we could not identify additional loci associated with breast cancer, our study utilized one of the largest sample sizes reported to date, and provided genetic status that represent the Japanese population. Further local and international collaborative study is essential to identify additional genetic variants that could lead to a better, accurate prediction for breast cancer.

Associations of dietary folate, Vitamins B6 and B12 and methionine intake with risk of breast cancer among African American and European American women

African American (AA) women are more likely than European American (EA) women to be diagnosed with breast cancer at younger ages and to develop poor prognosis tumors. However, these racial differences are largely unexplained. Folate and other methyl-group nutrients may be related to breast carcinogenesis, but few studies have examined these associations in AA populations. We examined the associations of dietary intake of these nutrients with breast cancer risk overall, by menopausal and estrogen receptor (ER) status among 1,582 AA (749 cases) and 1,434 EA (744 cases) women using data from a case-control study, the Women's Circle of Health Study. Unconditional multivariable logistic regression models were used to compute odds ratios (ORs) and 95% confidence intervals (CIs) for the association of each nutrient and breast cancer risk. In AA women, inverse associations were observed for natural food folate intake among premenopausal women (fourth vs. first quartile: OR = 0.57, 95% CI, 0.33-1.00; p for trend = 0.06) and for ER-positive tumors (fourth vs. first quartile: OR = 0.58, 95% CI, 0.36-0.93; p for trend = 0.03), whereas in EA women, a positive association was observed for intake of synthetic folate (fourth vs. first quartile: OR = 1.53, 95% CI, 1.06-2.21; p for trend = 0.03). Our findings suggest that natural food folate intake is inversely associated with breast cancer risk and that this association may vary by race, menopausal status or ER status. The finding of an increased risk observed among EA women with the highest intake of synthetic folate from fortified foods warrants further investigation.