Misconceptions about Vitamin A Consumption during Pregnancy

Vitamin A deficiency is one of the most common deficiency diseases in the world today, affecting millions of people. Despite this, it is widely believed that it should be avoided during pregnancy because of its harmful effects on the fetus. In this article, we will analyze in detail what led to this finding and what you can do to ensure that your unborn child is not deficient in vitamin A, without having to worry about excess.

The role of vitamin A in fetal development

Many people focus exclusively on the dangers of vitamin A in pregnancy, forgetting to mention that it is one of the most important vitamins for proper growth and healthy development, which is essential for embryo as well as mother. (1)

It is important for the development and health of the eye, while a lack of it can cause vision problems initially and even leads to blindness over time. (2)

Vitamin A is also crucial for healthy bones and teeth (3) and protects skin and mucus membranes from damage and pathogens. (4)

When deficient, white blood cells are unable to perform their functions, (5) which can have serious consequences at this critical time of life. 

A number of other negative effects of vitamin A deficiency in pregnancy have now been demonstrated:

• In animal models, vitamin A deficiency significantly increased the risk of later insulin resistance and glucose intolerance in adulthood, (6) and in women, of gestational diabetes. (7) In a Danish study, the risk of diabetes in the children of women who consumed more vitamin A during pregnancy was reduced. (8)
• Vitamin A supplementation during pregnancy also increased hemoglobin concentrations, reducing the incidence of gestational anemia.(9)
• Vitamin A deficiency in pregnancy leads to abnormal ear development, which can later lead to hearing loss, probably by increasing the risk of middle ear infections.(10)
• In the second trimester of pregnancy, vitamin A deficiency tripled the risk of schizophrenia and other mental illnesses. (11) 
• Severe vitamin A deficiency can cause children's kidneys to fail to develop properly, leaving them much smaller and unable to function properly. (12)
• Vitamin A supplementation before and during pregnancy has been shown to significantly improve lung function in children.(13) 
• In a similar study, vitamin A supplementation also had a positive effect on children's later school performance. (14)

Evidently, vitamin A deficiency in pregnancy can lead to a host of serious problems that most people don't even know about. This is because, according to health organizations, vitamin A deficiency only affects developing countries, while everyone in developed countries consumes plenty of it. In fact, this is coming into question as well. But before we get to the reasons, let's see why vitamin A is considered dangerous during pregnancy.

Misunderstood vitamin A

Interestingly, while the devastation of vitamin A deficiency is clearly visible in developing countries, in developed regions only the negative effects of vitamin A have been emphasized in recent decades. Over time, it has generally turned out that these were mostly based on unfounded fears and misconceptions, and in other cases were due to inappropriate supplementation of the vitamin.

To this day, we often hear that vitamin A is easily overdosed, but this is only true of the artificially produced and water-solubilized emulsified or solid forms, whereas we would need ten times the amount of the natural, fat-soluble form of vitamin A. (15) Overdosing with natural foods is almost unheard of, (16) and with supplements only when used inappropriately.

It was also popularly believed that a lack of vitamin A causes osteoporosis, (17) while it is essential for healthy bones and becomes highly protective when vitamin D levels are adequate. (3) 

It has also been suggested that it inhibits the utilization and function of vitamin D, but a later study has shown that when supplemented together, both are better utilized, (18) and that certain genes are affected in combination with vitamin D. (19)

Finally, in the 1990s, the idea that vitamin A is harmful to the fetus became widespread and has been in the public domain ever since: several health organizations still stress this and warn against its consumption, although, as we shall see, this idea stands on shaky ground.
How can an essential vitamin be a source of danger and harm to the fetus?

Synthetic retinoids

Certain synthetic vitamin A derivatives (isotretinoin, etretinate, acitretin) used as medicines to treat skin problems have been shown to have serious adverse effects on the fetus. (20,21,22)

These skin conditions often affect young women and, although the need to allow enough time between taking the drugs and having a baby is stressed, unplanned pregnancies have unfortunately caused problems in many cases.

It is important to note, however, that these medicines work in a completely different way to natural vitamin A, so they should not be lumped together.

Natural vitamin A (retinol)

In animal models, it has been observed for several decades that vitamin A metabolites are produced during metabolism that, above certain concentrations, can be potentially harmful to the fetus in early pregnancy. (23)

Studies that have demonstrated the adverse effects of vitamin A supplementation usually used extremely high doses: for example, one study used 35,000 IU per day in rats, which in humans would be equivalent to several million IU, more than 1,000 times the recommended daily intake. (24) 

As different animals have different metabolisms, it is not possible to draw precise conclusions for humans, but it has been shown in theory that there are levels of vitamin A high enough to cause a problem.

Natural protection of the fetus

The body uses several "defense" mechanisms to ensure that the fetus gets enough retinol, but only a small amount of potentially fetal-damaging metabolites. 
This is supported by several studies showing that fetal retinol levels did not increase significantly following maternal vitamin A supplementation, and even women supplementing with 30 000 IU of vitamin A per day had similar levels of the problematic metabolites as women delivering healthy babies. (25) 

Animal studies also show that even 30,000 IU per day in humans is a very low risk of birth defects, so the average intake in humans is much lower than is likely to cause any such problems. (26)

Why exactly do we need vitamin A during pregnancy? In small amounts, it is essential for embryonic development, but it also has another important function: during the last stages of pregnancy, significant amounts of vitamin A are directed to the breasts to provide the unborn baby with large amounts of vitamin A through breast milk after delivery. This is important because, like vitamin K, they are born with low levels of vitamin A. (27) 

Although in theory vitamin A can indeed be harmful to the fetus, it is important in any communication about it to clarify exactly what amount of vitamin A may be a problem, as well as the dangers of not consuming enough.  

To answer the first question, let's look at what we can learn from human studies.

Contradictory results on the harmful effects of vitamin A on fetus

The first research that essentially substantiated concerns about the adverse effects of vitamin A on the fetus was an observational study published in 1995, which examined the effects of vitamin A consumption and supplementation on birth defects in 22748 pregnant women. (28) It was found that intakes of more than 10,000 IU of vitamin A per day from supplements, or more than 15,000 IU of vitamin A from the diet, were already significantly harmful to the fetus.

Compared with vitamin A intakes of less than 5000 IU, intakes of 15000 IU or more were associated with a 3.5-fold increased risk, while supplement intakes of 10000 IU or more were associated with a 4.8-fold increased risk compared with intakes of less than 5000 IU. If this is indeed the case, then caution about vitamin A would indeed be warranted, but many questions have been raised about the study.

There has been a great deal of criticism of this research, some of which was addressed to the editor of the journal by other researchers. (29,30,31) In many cases, birth defects were informed by mothers who were not skilled in diagnosing them accurately, and they also included defects that were not known to be caused by vitamin A derivatives. There was also a problem that where accurate data were not available, estimates were simply used.

Overall, higher intakes of vitamin A caused very few birth defects, and even these were thought to have been misclassified. But even more importantly, no similar results have ever been found in older or more recent studies, casting the study in dubitable light.
In most cases, no significant association has been found between vitamin A supplementation, higher vitamin A intake and the incidence of birth defects, and there are plenty of studies that report a slight protective effect:

• In an older Spanish study, for example, only amounts higher than 40,000 IU per day increased risk, while lower amounts were found to be strongly protective. (32)
• In an intervention study, pregnant mothers who had previously given birth to a child with a birth defect associated with vitamin A overdose were given various vitamins, including 12500 IU vitamin A per day. Of the 48 mothers who did not receive extra vitamins, 5 had a newborn with a defect, while none of the mothers who supplementing 12500 IU of vitamin A and other vitamins per day had a newborn with a defect. (33)
• A study published in 1999 analyzed data from 424 pregnant women who supplemented with an average of 50,000 IU of vitamin A per day during early pregnancy (a critical time when excess vitamin A could be harmful to the fetus). Compared with a control group not consuming any fetal toxicants, vitamin A supplementation had no negative effect even at such high doses. (34)
• A year earlier, in a Hungarian study analyzing data from tens of thousands of women, vitamin A supplementation of between 5,000 and 10,000 IU per day was protective against birth defects that are partly attributed to over-supplementation. (35)

More recent studies on this issue were summarized in a meta-analysis published in 2022, which presents the pooled results of 6 studies. (36) These show that vitamin A supplementation provides a slight protection against birth defects. 

Exactly what doses were used is not clear from this study, but it is clear that in most cases higher vitamin A intakes were preferable. Of the 6 studies, only 1 was an older study in which higher vitamin A intake had a negative effect, (37) but at that time multivitamins contained much higher amounts of vitamin A. It is possible that this may have caused participants to consume tens of thousands of IU, especially if they also supplemented aside from the study or ate liver regularly. Apart from this, however, all other studies, most of them in Europe, have shown a protective effect.

So this confirms that vitamin A is something we do need during pregnancy, and that it is useful to supplement it if we don't consume too much. Multivitamins and prenatal vitamins used to contain as much as 10-25,000 IU per day, but nowadays they are generally much lower and are beneficial for everyone.

Confusion about official recommendations

Different health organizations and countries have quite different recommendations on vitamin A consumption and supplementation in pregnancy. 
While in developing countries 10,000 IU per day or 25,000 IU per week is recommended, in the more economically developed regions it is not recommended at all, although up to 5,000 IU per day is considered safe. 
In Finland, even the liver is said to be able to achieve an excess intake, but the problem is that without it, deficiency becomes more common. Indeed, liver is the best source of vitamin A, and if it were eliminated from our diets we would have to eat as much of other animal foods as very few people do.

Although beta-carotene found in plant foods also contributes to meeting our needs, its conversion efficiency varies widely between individuals and cannot be accurately determined without genetic testing. (38) Yet many nutritional information sites still label vegetables as the best sources of vitamin A, as beta-carotene and the true vitamin A (retinol) are mistakenly treated as one and the same. This is a big mistake, because beta-carotene is only about one-twelfth as useful as retinol, and other carotenoids even less so. (39)

This is illustrated by the fact that in the study mentioned at the beginning of this article, in which vitamin A supplementation improved lung function in children, but beta-carotene supplementation did not have a similar effect. (13) It is therefore advisable to consume preformulated vitamin A and not rely solely on beta-carotene.

Although health organizations say that vitamin A deficiency is not a problem in developed countries, this is far from certain. Most people do not eat liver, and many do not consume animal foods that contain vitamin A. Research in the 2022 meta-analysis shows that European pregnant women's vitamin A intake is inadequate, because if they were consuming enough, they would not benefit from higher intakes.

Summary and practical advice

Like other micronutrients, vitamin A is needed from the moment of conception, so ideally parents should make sure they get enough of it from much earlier on. We can store a lot of vitamin A in our livers, so if we have a good supply it will be available all the time, even if we hardly consume it for a few weeks or even a few months.

During pregnancy, especially in the first trimester, it is not recommended to consume more than 10,000 IU per day. Not because more than that would certainly be harmful, but because there is no additional benefit. However, it is safe to take this much, as a similar amount has never caused any problems. If you don't consume liver regularly, you should supplement with about 5000 IU per day, as this will prevent its deficiency and has no known disadvantage.

Another thing to bear in mind about liver consumption in the first trimester is that the vitamin A content of different livers can vary considerably. In one study, healthy women who consumed 120,000 IU of vitamin A from liver dishes had significantly increased concentrations of metabolites associated with birth defects. (40) Most livers contain much less vitamin A than this, but it may be prudent to eat only 25-50 grams of them occasionally and not to consume them every day. Also, it is worth choosing those with lower vitamin A content, such as chicken livers.

Towards the end of pregnancy, and especially during breastfeeding, it is safe to take more vitamin A, which is very important for children's vitamin A needs.

By following these simple rules, we don't have to worry about the harmful effects of vitamin A, while we can be sure that we won't have any problems with a deficiency.