Dietary supplements and vitamins during pregnancy.

According to the U.S. Congress in the Dietary Supplement Health and Education Act (DSHEA), passed into law in 19941, a dietary supplement is a product besides tobacco used to supplement the diet, and that has one or more dietary ingredients such as vitamins, minerals, and herbs, or their constituents. It also has to be taken by mouth as a pill, capsule, diet, tablet, or liquid, and labeled a dietary supplement on its front panel1. There are important issues concerning these products, in particular, those of safety and efficacy, particularly during pregnancy.

This is because of the lack of compulsory regulatory mechanisms for monitoring these attributes of dietary supplements even in countries such as the U.S., where for example, the Food and Drug Administration (FDA) has to prove that it must prohibit unsafe dietary supplements, and not the manufacturer that its product is safe1. Thus, it is difficult to determine the safety, and value of some dietary supplements, which may pose serious health risks to the pregnant woman and the fetus alike. Furthermore, some herbs may be toxic to both, hence the need for pregnant and lactating women to avoid taking herbs except recommended by their doctors and to ensure that such products indicate they were made with strict observance of Good Manufacturing Practices (GMP).

No doubt, there is need to exercise caution in the use of vitamins during pregnancy and lactation as well. The benefits of some vitamins in pregnancy are well established. Scholl and her colleagues2, for example recently reported their study on the effect of vitamin E on fetal growth. They measured maternal plasma concentrations of α- and γ-tocopherols in relation to fetal growth, and this link, associated maternal factors, of diet and supplement use to tocopherol concentrations at week 28 of gestation, controlled. The researchers found a positive correlation between plasma concentrations of α-tocopherol at entry and at week 28 and increased fetal growth (birth weight for gestation), a decreased risk of small-for-gestational-age births, and an increased risk of large-for-gestational-age births.

Their findings also showed, among others, a positive link between concentration of α-tocopherol at week 28 and the use of prenatal multivitamins and dietary intake of vitamin E. The researchers concluded that early and late circulating concentrations of α-tocopherol are positively linked to fetal growth. The findings of another recent study, an international retrospective cohort study of births monitored by birth defect registries that evaluated the effectiveness of policies and recommendations on folic acid aimed at reducing the occurrence of neural tube defects are actually instructive regarding the extent to which our knowledge of the benefits of vitamins for example, during pregnancy is actually making a difference3.

The researchers looked at thirteen birth defects registries monitoring rates of neural tube defects from 1988 to 1998 in Norway, Finland, Northern Netherlands, England and Wales, Ireland, France (Paris, Strasbourg, and Central East), Hungary, Italy (Emilia Romagna and Campania), Portugal, and Israel to ascertain cases of neural tube defects among liveborn infants, stillbirths, and pregnancy terminations (where legal), and via interviews and the literature, ascertained policies and recommendations in these countries.

On evaluating the incidences and trends in rates of neural tube defects before and after 1992 (the year of the first recommendations) and before and after the year of local recommendations (when applicable), the authors observed that recommendations on folic acid use did not result in any evident improvement in theses rates, and that in fact new cases of neural tube defects persisted, noting that recommendations alone did not appear to the rates up to six years after clinical trials confirmed the effectiveness of folic acid, a vitamin B, taken before conception in reducing the incidence of spina bifida and neural tube defects in newborns by as much as 80%, even more4, 5, 6.

The authors stressed the need to promptly incorporate food fortification with more robust implementation of the recommendations on vitamin supplements. With birth defects accounting for one in every four infant deaths and for many fetal deaths and pregnancy terminations7, 8, developing countries due to their large birth rates and limited healthcare resources shouldering most of the global burden of birth defects3, and folic acid being inexpensive and safe, research showing it could indeed, reduce the rates of other major birth defects9, the use of folic acid by women planning a pregnancy or throughout childbearing age is doubtless, desirable.

As the research mentioned earlier shows, so also is the current practice in countries such as the U.S., Canada, Chile, and South Africa, the integration of folic acid use with a policy of pervasive fortification of flour to facilitate the consumption by all, of at least a small extra quantity of folic acid access or otherwise to supplements, notwithstanding. Yet, vitamins are not always beneficial during pregnancy, vitamin A, for example, is important for our well being, but its analogue, isotretinoin, or Accutane, used to treat acne, has been shown to cause birth defects in humans and animals10, 11.

Furthermore, vitamin A intake in large doses during pregnancy could also cause birth defects as could its analogues also used in large doses11, more than 8,000 IU for a pregnant woman uncalled for and not recommended. Incidentally, foods that are rich in beta-carotene can provide the needed amount of vitamin A and they are not linked to toxicity11.

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