[Effect of folic acid and folinic acid on zinc absorption]

Is the Tradeoff between Folic Acid or/and Multivitamin Supplementation against Birth Defects in Early Pregnancy Reconsidered? Evidence Based on a Chinese Birth Cohort Study

BACKGROUND

Several studies have reported conflicting results on the association between maternal exposure to folic acid (FA) and/or multivitamin (MV) supplements and the risk of birth defects (BDs), especially for different subtypes of BDs. The present study aimed to identify the association between maternal exposure to FA or/and MV and BDs in offspring.

METHODS

In the Chinese Birth Cohort Study initiated from 20 November 2017, 120,652 pregnant women completed follow-up until 20 August 2021. The participants were classified into four groups: without exposure to FA and MV, exposure to only FA, exposure to only MV, and exposure to FA and MV. Birth defects were coded by the International Classification of Diseases (ICD)-10. In order to explore the structural relationship between maternal FA or MV supplements and BDs, directed acyclic graphs were drawn. Then, an inverse probability treatment weighting was utilized to reduce the systematic differences in the baseline characteristics among the different groups. Lastly, a two-level mixed-effect log binomial regression analysis was used to estimate the relative risk (RR) value of the different subtypes of BDs under different exposures to FA and/or MV.

RESULTS

Compared with the maternal group without exposure to FA and MV, the RR values of nervous system defects, face, ear, and neck defects, limb defects, and CHDs in the maternal group with only FA supplementation were less than 1.0, but they were not statistically significant. The RR values of genitourinary defects, abnormal chromosomes, and oral clefts were more than 1.0, and they were also not statistically significant. However, the risk of genitourinary defects (RR: 3.22, 95% CI: 1.42-7.29) and chromosomal abnormalities (RR: 2.57, 95% CI: 1.16-5.73) in the maternal group with only MV supplementation increased more than those in the maternal group without exposure to FA and MV. In addition, the RR values of all subtypes of BDs in the maternal group with exposure to FA and MV were closer to 1.0 than those in maternal group with exposure to only MV, but they were not statistically significant.

CONCLUSIONS

It was indicated that the simultaneous supplementation of FA and MV in early pregnancy may have an interaction for the prevention of BDs and may have inconsistent effects for different subtypes of BDs. At the same time, excessive FA supplementation in pregnant women may increase the risk of BDs in their offspring. Although the mechanism is not clear, this evidence reminded us that more trade-offs are necessary for formulating strategies for the prevention of BDs with FA and/or MV supplementation in early pregnancy.

Zinc supplementation does not alter plasma homocysteine, vitamin B12 and red blood cell folate concentrations in French elderly subjects

BACKGROUND/AIMS

In ageing, low folates and vitamin B12 status are frequent and can explain the increase of plasma homocysteine level. Zinc is involved in the folates and vitamin B12 metabolism with opposite actions. The aim of this study was to investigate the effects of zinc supplementation on homocysteine and vitamin B12 plasma levels as well as red blood cell folate level in French ageing subjects participating in the ZENITH study.

METHODS

Apparently healthy middle-aged (55-70 years) and free-living older (70-85 years) subjects were enrolled. They were randomly allocated to three groups: 0, 15 or 30 mg Zn per day for 6 months as zinc gluconate in addition to their usual dietary intake.

RESULTS

At baseline, plasma homocysteine levels (15.2+/-3.5 micromol/L) in older people were higher than in the middle-aged subjects (12.7+/-2.7 micromol/L) and was negatively correlated with vitamin B12 values (p=0.0036, r=-0.215) and with RBC folate levels (p<0.0001, r=-0.30). These results are in agreement with previous data. However, we found no correlation between the biomarkers of zinc status and homocysteine, vitamin B12 or folate levels at baseline. Moreover, 6-month zinc supplementation did not modify homocysteine, vitamin B12 and RBC folate values in either of the groups.

CONCLUSIONS

Zinc supplementation at moderate doses do not lead to deleterious effect on folate or vitamin B12 status in ageing healthy free-living people, but does not have any beneficial effects on homocysteine metabolism either.

Folic acid enrichment of bread does not appear to affect zinc absorption in young women

BACKGROUND

In several countries cereals are now enriched with folic acid to reduce the risk of neural tube defects. Human studies suggest that folic acid interferes with zinc absorption. This raises concerns about the zinc status of high-risk groups such as infants, pregnant women, and older persons.

OBJECTIVE

We sought to determine the effect of added folic acid on zinc absorption from white bread with high and low zinc contents.

DESIGN

Zinc absorption was measured in 15 healthy women (22-33 y), each of whom consumed 4 single meals spaced 2 wk apart in a randomized crossover design. The servings of bread (100 g) differed in zinc and folic acid contents as follows: A, 1.2 mg Zn and 17 microg folic acid; B, 1.2 mg Zn and 144 microg folic acid; C, 3.0 mg Zn and 17 microg folic acid; and D, 2.9 mg Zn and 144 microg folic acid. Meals were extrinsically labeled with 65Zn and absorption was estimated from whole-body retention measurements. Folate status was assessed by measuring plasma and erythrocyte folate and plasma homocysteine concentrations.

RESULTS

Mean (+/-SD) zinc absorption did not differ significantly in relation to the folate content of the breads at either the low zinc content (38.8 +/- 13.5% and 40.6 +/- 16.5% for A and B, respectively; P = 0.74) or the high zinc content (26.7 +/- 9.3% and 22.7 +/- 6.6% for C and D, respectively; P = 0.16). There was no significant correlation between folate status and zinc absorption (r < 0.3, P > 0.1).

CONCLUSION

Fortification of white bread with a commonly used amount of folic acid did not appear to influence zinc absorption at either a high or a low zinc content.

Interactions related to trace elements in parenteral nutrition

Trace elements (TE) are now commonly added into the nutritive admixtures used in total parenteral nutrition (TPN) to prevent deficiencies which can be observed in patients undergoing long-term intravenous feeding. Although the needs in TE are not exactly known during a TPN, some of them must be considered as essential according to the results of studies dealing with general nutritional deficiencies. Among essential TE copper, iron and zinc are found at relatively high levels in organism. Chromium, manganese and selenium are also very important even though they are present at lower levels. In the case of a parenteral nutrition, the composition of the mixture is precisely defined and both digestion and absorption steps are shunted. Nevertheless, beneficial and/or negative physicochemical and metabolic interactions can occur between TE and the other nutrients. These interactions must be studied and taken into account because they can modify the bioavailability of the trace elements. In this article, our aim is to review the main recent bodies of knowledge which could be helpful to understand and prevent nutritional problems linked to these interactions during parenteral nutrition.