The effect of vitamin D supplementation on oxidative stress and inflammatory biomarkers in pregnant women: a systematic review and meta-analysis of clinical trials

Background

Vitamin D deficiency, a common problem among pregnant women, is linked with maternal inflammation, oxidative stress and consequent adverse pregnancy outcomes. The aim of this systematic review was to evaluate the effect of vitamin D supplementation on oxidative stress and inflammatory biomarkers in pregnant women according to the PRISMA guidance.

Methods

Four databases including PubMed/MEDLINE, Scopus, Web of Science and Cochrane were used for searching papers published until 25^th July 2022. Clinical trials that assessed 25-Hydroxyvitamin D (25(OH)D), inflammatory markers (including high sensitivity C-reactive protein (hs-CRP) and certain cytokines) and oxidative stress markers (including malondialdehyde (MDA), total antioxidant capacity (TAC) and glutathione (GSH)) in pregnant women, were included in this review. The primary search of three databases displayed 21571 records. After removing duplicates and irrelevant articles, 17 eligible RCTs included for more evaluation. Random effect model and Der Simonian-Laird method were used to pool the data of studies. Risk of bias assessed according to version 2 of the Cochrane risk-of-bias tool for randomized trials.

Results

According to the meta-analysis result, vitamin D supplementation caused a significant increase in the maternal circulating concentrations of 25(OH)D (SMD 2.07; 95%, CI 1.51, 2.63; p < 0.001), TAC (SMD 2.13, 95% CI 1.04 to 3.23, p < 0.001) and GSH (SMD 4.37, 95% CI 2.9 to 5.74, p < 0.001) as well as a significant decrease in the levels of MDA (SMD -0.46, 95% CI -0.87 to -0.05, p = 0.02). However, it had no significant impact on hs-CRP concentrations (SMD 0.24; 95% CI, -0.55, 1.03; p = 0.50).

Conclusion

In the present study, vitamin D supplementation led to increased levels of 25(OH)D, TAC and GSH and also decreased concentration of MDA. Nevertheless, because of low certainty of evidence, these findings have to be declared conservatively.

Trial registration

Registration code in PROSPERO website: CRD42020202600

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-05132-w.

Effect of latitude on seasonal variations of vitamin D and some cardiometabolic risk factors: national food and nutrition surveillance

Background

Despite a remarkable reduction in the occurrence of many micronutrient deficiencies in most countries, vitamin D deficiency has remained a global problem. Age-adjusted disability-adjusted life years lost due to cardiovascular disease in the Eastern Mediterranean Region, including in the Islamic Republic of Iran, are higher than the global average.

Aims

To assess the effects of latitude and season on vitamin D status in the Iranian population and the association between vitamin D status and certain cardiometabolic risk factors.

Methods

A sample of 1111 participants aged 19-65 years was randomly selected from 6 regions with latitudes ranging from 29º.0 N to 37.5º N. All anthropometric and biochemical assessments were performed twice a year, summer and winter during 2013 to 2014.

Results

Overall mean 25(OH)D concentration was 26.9 [standard deviation (SD) 17.8] nmol/L in winter and 43.4 (SD 32.9 nmol/L in summer (P < 0.001). Poor vitamin D status was noticeable in both seasons (90.1% and 69.2%, respectively). Being male (B, 7.6; 95% CI: 4.3 to 10.8; P < 0.001) and living at a latitude higher than 33 ° were positive predictors, and serum 25(OH)D concentration in winter (B, -0.2; 95% CI: -2.9 to -0.11; P < 0.001) was a negative predictor of changes of 25(OH)D concentrations.

Conclusion

We found a high prevalence of suboptimal vitamin D status in Iranian adults throughout the year, irrespective of latitude and season. Improvement of mean circulating 25(OH)D concentrations in the community to 50+ nmol/L through a fortification programme is likely to engender healthy cardiometabolic changes.

Elevated Bioactivity of the Tolerogenic Cytokines, Interleukin-10 and Transforming Growth Factor-β, in the Blood of Acutely Malnourished Weanling Mice

The main objective of this investigation was to determine the influence of acute deficits of protein and energy on the blood levels of interleukin-10 (IL-10) and transforming growth factor-β (TGF-β), physiologically the main anti-inflammatory and tolerogenic cytokines. In four 14-day experiments, male and female C57BL/6J mice, initially 19 days old, consumed a complete purified diet either ad libitum or in restricted daily quantities, or had free access to an isocaloric purified low-protein diet. A zero-time control group (19 days old) was included. In the first two experiments, serum IL-10 levels were assessed by sandwich enzyme-linked immunosorbent assay (ELISA) and bioassay. The mean serum IL-10 bioactivities were higher (P ≤ 0.05) in both malnourished groups (low-protein and restricted intake: 15.8 and 12.2 ng/ml, respectively) than in the zero-time and age-matched control groups (6.3 and 7.3 ng/ml, respectively), whereas serum IL-10 immunoactivity was high only in the restricted intake group (e.g., second experiment: 17.0 pg/ml vs. 5.4, 3.7, and 3.1 pg/ml in the zero-time control, age-matched control and low-protein group, respectively). The third and fourth experiments centered on plasma TGF-β immunoactivity (sandwich ELISA) and bioactivity, respectively. The ELISA revealed a high mean plasma TGF-β1 level (P < 0.05) in the low-protein group only, but TGF-β bioactivity (β1 isoform, although 15% β2 in the restricted intake group) was high in both malnourished groups (8.7 and 9.3 ng/ml in the low-protein and restricted groups, respectively) relative to the age-matched control group (0.5 ng/ml). Thus, metabolically distinct weanling systems mimicking marasmus and incipient kwashiorkor both exhibit a blood cytokine profile that points to a tolerogenic microenvironment within immune response compartments. A model emerges in which malnutrition-associated immune competence, at least in advanced weight loss, centers on cytokine-mediated peripheral tolerance that reduces the risk of catabolically induced autoimmune disease, but this is at the cost of attenuated responsiveness to infectious agents.

Iron and vitamin C co-supplementation increased serum vitamin C without adverse effect on zinc level in iron deficient female youth

BACKGROUND

Iron supplementation can decrease the absorption of zinc and influence other antioxidants levels such as vitamin C. This study aimed to investigate the effect of iron supplements alone and in combination with vitamin C on zinc and vitamin C status in iron deficient female students.

METHODS

In a double-blind randomized clinical trail, 60 iron deficient students were selected from 289 volunteers residing in dormitory. After matching, subjects were randomly assigned into two groups: Group I (50 mg elemental iron supplements) and Group II (50 mg elemental iron + 500 mg ascorbic acid). Serum ferritin, iron, serum zinc, and plasma vitamin C concentrations were measured by using enzyme-linked immunosorbent assay, spectrophotometer, atomic absorption spectrometer, and colorimeter, respectively after 6 and 12 weeks supplementation. Student's t-test and repeated measures analysis of variance were applied to analyze the data using SPSS software.

RESULTS

Serum zinc levels had no significant differences between 2 groups at the baseline; however, its concentration decreased from 80.9 ± 4.2-68.9 ± 2.7 μg/dl to 81.2 ± 4.5-66.1 ± 2.9 μg/dl (P < 0.001) in Groups I and II, respectively after 6 weeks of supplementation. Continuous supplementation increased serum zinc concentration to baseline levels (79.0 ± 2.9 μg/dl; P < 0.01) in Group I and 70.5 ± 3.1 μg/dl in Group II following 12 weeks of supplementation. Plasma vitamin C increased from 3 ± 0/1-3.3 ± 0.2 mg/dl to 2.7 ± 0. 1-4.2 ± 0.2 mg/dl (P < 0.01) in Groups I and II, respectively. At the end of study, plasma vitamin C significantly increased from 3.3 ± 0.3-4.7 ± 0.3 (P < 0.01) to 4.2 ± 0.2-7.1 ± 0.2 (P < 0.001) in Groups I and II, respectively.

CONCLUSIONS

Iron supplementation with and without vitamin C led to reduction in serum Zn in iron-deficient female students after 6 weeks. However, the decreasing trend stops after repletion of iron stores and Zn levels returned to the approximately baseline values after 12 weeks.

The effects of green tea consumption on metabolic and anthropometric indices in patients with Type 2 diabetes

BACKGROUND

This study aims at investigating the possible effects of different daily doses of green tea (GT) intake for eight weeks on certain anthropometric, metabolic, and oxidative stress biomarkers of diabetic patients.

MATERIALS AND METHODS

This randomized clinical trial included 63 patients with type 2 diabetes (30 males and 33 females). After a two-week run-in period without green tea, they were randomly assigned into one of the three groups, with a different daily intake of green tea; four cups of green tea per day (n = 24), two cups of green tea per day (n = 25), and the control group (n = 14) with no green tea intake for two months. At baseline and after the intervention, blood tests, dietary, and anthropometric variables were assessed. The patients were instructed to maintain their usual dietary intake and normal physical activity.

RESULTS

Consumption of four cups of GT per day caused a significant decrease in body weight (73.2 to 71.9) (P < 0.001), body mass index (27.4 to 26.9) (P < 0.001), waist circumference (95.8 to 91.5) (P < 0.001), and systolic blood pressure (126.2 to 118.6) (P < 0.05) in this group. No significant change was seen in the other groups and between group comparisons. The metabolic and oxidative stress parameters did not show any significant differences within and between groups.

CONCLUSION

Drinking four cups of green tea led to a significant reduction in weight and systolic blood pressure.

The effect of iron-vitamin C co-supplementation on biomarkers of oxidative stress in iron-deficient female youth

There is no study that assessed the effect of co-supplementation of iron and vitamin C on biomarkers of oxidative stress in non-anemic iron-deficient females. We investigated the effects of iron vs. iron + vitamin C co-supplementation on biomarkers of oxidative stress in iron-deficient girls. In a double-blind randomized controlled clinical trial, performed among 60 non-anemic iron-deficient girls, participants were randomly assigned to receive either 50 mg/day elemental iron supplements or 50 mg/day elemental iron + 500 mg/day ascorbic acid for 12 weeks. Fasting blood samples were taken at baseline, weeks 6 and 12 for assessment of biomarkers of oxidative stress. Compared with the baseline levels, both iron and iron + vitamin C supplementation resulted in a significant reduction in serum malondialdehyde (MDA) levels (P time < 0.001) and remarkable elevation in serum total antioxidant capacity (TAC; P time < 0.001) and vitamin C levels (P time = 0.001); however, comparing the two groups we failed to find an additional effect of iron + vitamin C supplementation to that of iron alone on serum TAC and MDA levels (P group was not statistically significant). Iron + vitamin C supplementation influenced serum vitamin C levels much more than that by iron alone (P group < 0.01). We also found a significant interaction term between time and group about serum vitamin C levels while this interaction was not significant about serum TAC and MDA levels. In conclusion, we found that iron supplementation with/without vitamin C improve biomarkers of oxidative stress among non-anemic iron-deficient females and may strengthen the antioxidant defense system by decreasing reactive oxygen species. Co-supplementation of iron + vitamin C has no further effect on oxidative stress compared with iron alone.

Validity and reproducibility of a food frequency questionnaire for assessment of fruit and vegetable intake in Iranian adults(*)

BACKGROUND

This study's aim was to design and validate a semi-quantitative food frequency questionnaire (FFQ) for assessment of fruits and vegetables (FV) consumption in adults of Isfahan by comparing the FFQ with dietary reference method and blood plasma levels of beta-carotene, vitamin C, and retinol.

METHODS

This validation study was performed on 123 healthy adults of Isfahan. FV intake was assessed using a 110-item FFQ. Data collection was performed during two different time periods to control for seasonal effects, fall/winter (cold season) and spring/summer (warm season). In each phase a FFQ and 1 day recall, and 2 days of food records as the dietary reference method were completed and plasma vitamin C, beta-carotene and retinol were measured. Data was analyzed by Pearson or Spearman and intraclass correlations.

RESULTS

Serum Lipids, sex, age, body mass index (BMI) and educational level adjusted Pearson correlation coefficient of FV with plasma vitamin C, beta-carotene and retinol were 0.55, 0.47 and 0.28 in the cold season (p < 0.05) and 0.52, 0.45 and 0.35 in the warm season (p < 0.001), respectively. Energy and fat intake, sex, age, BMI and educational level adjusted Pearson correlation coefficient for FV with dietary reference method in the cold and warm seasons were 0.62 and 0.60, respectively (p < 0.001). Intraclass correlation for reproducibility of FFQ in FV was 0.65 (p<0.001).

CONCLUSIONS

The designed FFQ had a good criterion validity and reproducibility for assessment of FV intake. Thus, it can serve as a valid tool in epidemiological studies to assess fruit and vegetable intake.

Validity of predictive equations for resting energy expenditure among Iranian women

OBJECTIVES

To determine the resting metabolic rate (RMR) in a sample of Iranian women, and to evaluate the validity of predictive equations for estimating RMR in normal and obese subjects.

METHODS

This cross-sectional study was conducted on a total of 187 healthy women aged 18-45 years. Anthropometric data were collected and subjects' RMR was measured by indirect calorimetry for 15 minutes following an overnight fast. RMR was also predicted using various types of formulas based on subjects' height, age, weight or fat-free mass. Body composition was estimated by bioelectric impedance analysis (BIA).

RESULTS

Measured RMR (mean ± SD) was found to be 1473 ± 296 kcal/day. The abbreviation formula overestimated RMR, while other formulas underestimated it. Harris-Benedict formula was valid among all BMI categories (normal weight, overweight, obese and morbidly obese). Two Schofield formulas were valid in normal weight, overweight and morbidly obese subjects; and Cunningham formula was valid only among overweight and obese women. Overweight and obese Iranian women had higher RMR in comparison with normal weight subjects (p<0.01); although after age and weight adjustment, the differences were not significant in any of the BMI categories.

CONCLUSIONS

The Harris-Benedict for mula provides a valid estimation of RMR at the group level in a range of normal-weight to morbidly obese Iranians. However, at the individual level, errors might be so high that using a measured value has to be preferred over an estimated value.

Relationship between obesity and periodontal status in a sample of young Iranian adults

AIM

To examine the possible relationship between body weight and periodontal disease in a sample of the young Iranian population.

DESIGN

An analytical (Case-Control) study.

PARTICIPANTS

Eighty individuals aged 18 to 34 years (40 normal and 40 overweight and obese subjects) were evaluated in this study.

METHODS

The periodontal examination consisted of: Plaque Index (PLI), Probing Pocket Depth (PPD) and Clinical Attachment Level (CAL). Body Mass Index (BMI) and Waist circumference (WC) were used as measures of overall and abdominal fat content. Socio-demographic variables and periodontal disease risk factors (age, gender, education, time elapsed since last dental visit, smoking and diabetes) were evaluated as covariates. The statistical tests used were: Kolmogorov-Smirnov, Independent Samples T-test, ANOVA, Exact fisher, Chi-Square test and Spearman's rank correlation (Rsp).

RESULTS

PPD and CAL were significantly higher in the case group compared to control (2.82 +/- 0.4 versus 2.56 +/- 0.36, P < 0.002 and 1.98 +/- 0.5 versus 1.63 +/- 0.335, P < 0.000 respectively). Subjects with a high waist circumference had significant differences of PPD and CAL when compared to normal waist circumference subjects (P < 0.000). There were also positive correlations between measures of overall fat content BMI and PPD (Rsp = 0.33), CAL (Rsp = 0.39) and age (Rsp = 0.42) on one side and the measure of WC and PPD (Rsp = 0.32), CAL (Rsp = 0.44), age (Rsp = 0.48) and PLI (Rsp = 0.3) on the other.

CONCLUSION

The results indicate that overall and abdominal obesity were associated with the extent of periodontal disease in a sample of Iranian young individuals and therefore prevention and management of obesity may be an additional factor for improving periodontal health.