Vitamin A

Good day, Mr. Jelinek,

I would like to inquire about vitamin A during pregnancy. I have read a book by Sally Fallon - The Nourishing Traditions, Book of Baby and Child Care, which indeed refutes studies about the harmfulness of vitamin A. On the contrary, it warns against the deficiency of this vitamin, which can lead to developmental defects of the fetus and miscarriage. The author recommends the consumption of liver and fish oil for optimal fetal development. I am interested in where the truth lies, and on which studies your recommendation to avoid vitamin A is based. For completeness, I am providing information from the book.

Thank you very much.

Here is a citation from the book:
VITAMIN A AND FETAL DEVELOPMENT

The U.S. Food and Drug Administration (FDA) and other government agencies warn pregnant women to avoid foods like liver and cod liver oil, claiming that too much vitamin A from these foods can cause birth defects.

The claim that intakes of vitamin A over 10,000 IU per day can increase the risk of birth defects can be traced back to a 1995 paper published by a group of researchers at Boston University. The researchers followed almost twenty-three thousand women over the course of their pregnancies and found that women who consumed more than 10,000 IU vitamin A during the first trimester gave birth to offspring with a greater risk of certain types of birth defects.

However, the study had some serious flaws. Most of the vitamin A came from multivitamins. The authors did not distinguish between various food sources—and most “food” vitamin A comes from fortified breakfast cereals—so the cause of the birth defects may well have been something else in the multivitamins or in the cereals. Three groups of experts wrote to the journal questioning the authors’ classification of the types of defects.

Most importantly, the authors may have underestimated the rate of certain types of birth defects in the group with low vitamin A intake. The rate of total birth defects among the twenty thousand women consuming less than 10,000 IU was only 1.5 percent; by contrast, the generally accepted background rate is 3-4 percent. The rate of defects among the three thousand women consuming more than 10,000 IU of vitamin A was 3 percent—on the lower end of normal.

The most serious objection to this study is the fact that it conflicts with all the other evidence. For example, a 1990 study conducted in Spain found that among twenty-five thousand births, doses of vitamin A over 40,000 IU per day carried a 2.7-fold higher risk of birth defects, but doses of vitamin A up to 20,000 IU or between 20,000 and 40,000 IU both carried a 50 percent lower risk of birth defects compared to no supplementation.

A 1996 study of over five hundred thousand births found that the children of women supplementing with at least 10,000 IU of vitamin A in addition to a multivitamin had a lower risk of birth defects than those of women who did not supplement, although the association could not be distinguished from the effects of chance.

A 1997 study of fifteen hundred births found no relationship between birth defects and use of vitamin A supplements, fortified breakfast cereals, organ meats or liver.

A 1999 prospective study of three hundred eleven mothers who consumed between 10,000 and 300,000 IU of vitamin A in the first trimester and a similarly sized group that did not supplement with vitamin A found no evidence of an increased risk of major malformations with increasing dose. The median dose was 50,000 IU.

The supplemented group as a whole had a 50 percent lower risk of major malformations than those who did not supplement, and there were no major malformations in offspring born to mothers consuming more than 50,000 IU.

The preponderance of the evidence clearly favors the view that 20,000 IU of supplemental vitamin A per day during pregnancy is safe and may even reduce the risk of birth defects.

The issue of recommended daily allowances (RDAs, or reference intake values) is somewhat unfortunate because it is related to an averaged population, thereby sidelining the requirements of individuals as metabolic individualities. The result in practice is situations where each study demonstrates slightly different results, and these discrepancies are further magnified in significance by differing interpretations. In such studies, it is also necessary to distinguish situations where the precisely defined intake of a given substance is assessed (which can only be achieved through the use of dietary supplements) or monitor the proportion of nutrients in the diet, where it is impossible to define specific values, as we never know how much of a monitored substance is found in foods (we can always only assess an average, which is moreover highly approximate).

With vitamin A, I personally do not see an issue with its overdose in terms of negative health impacts (such situations are relatively rare and almost always relate to inappropriate handling of dietary supplements). However, higher doses during pregnancy seem to contribute to fetal growth (larger babies are born, which is understandably a source of birth complications). This information can still be disputed, as it appears that higher doses of other micronutrients may also be responsible for this effect, which is generally an issue with the use of primarily multivitamins. The fact is, in the last two decades, supplement manufacturers have been following legislative regulations, which hold that higher doses of vitamin A during pregnancy are risky and have enshrined this within the health claims that may/must be presented with supplements.

In terms of development principles, it is clear that opinions based on new studies will continue to emerge; however, it generally holds true that at the legislative level, it always takes a longer time for any (significant) change to occur—especially when it involves situations related to public health.