Should Plant-Based Women Supplement with DHA During Pregnancy?

A systematic review of randomized controlled trials of DHA supplementation of pregnant and breastfeeding women failed to find any clear and consistent short- or long-term benefit for psychomotor, mental, visual, or physical development. Perhaps DHA supplementation during pregnancy has no effect because the body wisely protects the growth of the baby’s brain by drawing off of maternal stores of DHA, upregulating maternal DHA synthesis, and preferentially shuttling it to the fetus. But what if moms don’t start out with large maternal stores? In other words, maybe DHA failed to help women who were already getting enough, but perhaps women with very low intakes would benefit from DHA supplementation. My video Should Vegan Women Supplement with DHA During Pregnancy? explores the evidence available to date.

It’s interesting to note that, by 1978, researchers already were suggesting a plant-based diet as the diet of choice in the treatment of our number-one killer, heart disease, but babies breastfed by vegan moms had significantly less DHA in their bloodstreams, presumably because the moms had significantly less DHA in their breast milk.

The question is whether these differences are of any consequence. The growth and development of vegan and vegetarian born children are normal as long as they’re getting their B12, and “[t]here is no evidence that neural or intellectual functions are impaired.” In fact, the two studies we have on kids in vegetarian communities showed they had higher IQs, though that may be because their parents tended to be better educated. However, even though the kids seemed fine, that doesn’t rule out the possibility that there may be some “subtle differences…in visual or neural functioning.”

It would be interesting to compare the function of babies getting vegan breast milk levels versus general population levels. In one of the studies I profile in my video, it shows that vegans hit a level of 14, vegetarians 30, and omnivores 37. Another study compared 0 to 32, 64, and 96, and, though 32 worked better than 0, more than 32 didn’t add anything. This could explain why the general population at 37 doesn’t benefit from additional DHA supplementation. But what about down at 14? Most studies at that level show no advantage over 0, though one study found a benefit supplementing at as low as 5, but that doesn’t help us.

Just because babies breastfed by vegan moms have significantly lower DHA levels in the blood, that doesn’t necessarily mean they have lower levels in their brain, which is where it counts. What we need is a randomized, controlled trial in non-fish-eaters of DHA supplementation. Until then, it’s going to remain uncertain. So, what should pregnant and breastfeeding women who avoid fish do in the meanwhile? Low intake of DHA doesn’t “necessarily equate with fetal DHA inadequacy,” but new data suggest that some infants may not be getting enough and could benefit from their moms supplementing. Given this, I recommend pregnant and breastfeeding women on plant-based diets to follow the consensus guidelines to get about 200mg of preformed DHA from an uncontaminated source, like algae oil, which is probably the best combination for all women given the state of our world to minimize exposure to toxic pollutants such as dioxins, PCBs, and mercury. 


To gain a better understanding of why algae oil is better than purified fish oil, I encourage you to watch my video Should Pregnant and Breastfeeding Women Take DHA.

I’ve discussed concerns about pollutants in seafood during pregnancy in a number of my videos:

Finally, for more on taking long-chain omega-3s to protect your heart, see: 

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Should Pregnant and Breastfeeding Women Take DHA Supplements?

One of the reasons breastfed infants may have better cognitive and visual development is because human milk contains long-chain, polyunsaturated fatty acids like the omega-3 DHA, while most available infant formulas do not, based on data I discuss in my video Should Pregnant and Breastfeeding Women Take DHA?. Infants given control formula without DHA didn’t do as well as those given DHA-fortified formula, and neither group did as well as the breastfed infants, who serve as the “gold standard.” This was enough to convince formula manufacturers to start adding DHA to their infant formula starting back in 2002.

The question then became how much to add? Easy, right? Just add the amount that is naturally found in breast milk. However, the DHA level in breast milk is extremely variable depending on what the mom is eating. There are a number of healthy populations who don’t eat any seafood, for example, and they have much lower levels in their milk yet seem fine. So this makes it difficult to determine the optimal amount to add to formula or, for that matter, what to recommend for pregnant and breastfeeding women. “Consensus guidelines recommend that women should aim to consume an average of 200 mg” of DHA daily during pregnancy. “Simply encouraging pregnant women to eat more fish is not so simple, because most fish are to some extent contaminated” with toxic pollutants, such as mercury. (See my video Mercury vs. Omega-3s for Brain Development for more on this.) For most fish, such as tuna, the brain damage caused by the mercury would exceed the benefit from the DHA.

Additionally, some pollutants, like PCBs, can get stuck in our bodies for decades, so it’s not enough to just eat clean during pregnancy.

What about purified fish oil? The methods supplement manufacturers use, like distillation, leave considerable amounts of PCBs and other pollutants in the products, so much so that when taken as directed, salmon, herring, and tuna oils would exceed the tolerable daily intake of toxicity.

Thankfully, one can get the benefits without the risks by getting DHA from algae instead, which is where the fish eventually get it from themselves. So, pregnant and breastfeeding moms can cut out the middle-fish and get DHA directly from the source—at the bottom of the food chain where we don’t have to worry about toxic pollutants.

Until recently, we thought everyone should take these long-chain omega-3s for their heart. However, the balance of evidence is now such that doctors “should not recommend fish oil intake or fish consumption solely for the primary or secondary prevention of CHD,” coronary heart disease. But what about for expectant and breastfeeding mothers? What does the latest science show? Putting all the studies together, it turns out adding DHA to formula does not appear to help infant cognition after all, similar to other recent compilations of evidence that show “no significant benefit.” In fact, at least four meta-analyses, or systematic reviews, have reached a similar conclusion. These were based mostly on the standard series of measurements known as the Bayley Scales for Infant Development. If other tests were used, would there be different results? So far, no. Giving women DHA supplements during pregnancy did not appear to help with other outcomes, like attention span or working memory, either.

Although there may be no significant benefit to infant cognition, what about other things like vision? Six trials have been done to date supplementing pregnant women. Four showed no effect, and the two trials that showed benefit had some problems. So, while we really don’t know at this point, if all the studies so far show either nothing or benefit, why not just take them to err on the side of caution?

There may not be any demonstrable “clear and consistent” benefits, but there are new studies on this coming out all the time. If it’s harmless, maybe women should just take it to be on the safe side? The problem is that it may not be harmless in large doses. In a study in which women were given a whopping 800mg of DHA a day during pregnancy, infant “girls exposed to higher-dose DHA in utero [in the womb] had lower language scores and were more likely to have delayed language development than girls from the control group.”

So, the “absence of clear positive effects and the possible presence of negative effects in the children raise the question whether DHA supplementation is justifiable…” But it was a really large dose, suggesting that there may be “an optimum DHA level below and above which DHA might be detrimental to the developing brain.”


So, maybe too much is detrimental, but what about too little? I discuss that in Should Vegan Women Supplement with DHA During Pregnancy.

Other videos on the concerns about the pollutants in the aquatic food chain include:

For more on fish oil, see:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Do Flaxseeds Offer Sufficient Omega-3’s for Our Heart?

According to two of perhaps the most credible nutrition authorities, the World Health Organization and the European Food Safety Authority, we should get at least half of a percent of our calories from the essential omega-3 fat ALA. That’s easy: Just have about one tablespoon a day of chia seeds or ground flaxseeds and you’re all set.

Our body can then take the short-chain ALA from our diet and elongate it into the long-chain omega-3s, EPA and DHA. The question, however, has long been whether our bodies can make enough EPA and DHA for optimal health. How would one determine that? Take fiber, for example. “A convincing body of literature showed an increased [heart disease] risk when diets were low in fiber,” so the Institute of Medicine came up with a recommendation for about 30 grams a day, which is an intake observed to protect against coronary heart disease and to reduce constipation. “Thus, just as [cardiovascular disease] was used to help establish an [adequate intake] for dietary fiber,” it was also used as a way to develop a recommendation for EPA and DHA, as I discuss in my video Should We Take EPA and DHA Omega-3 for Our Heart?.

With reviews published as late as 2009 suggesting fish oil capsules may help with heart disease, nutrition authorities recommended an additional 250 mg per day of preformed EPA and DHA, since, evidently, we were not making enough on our own if taking more helped. So, in addition to the one or two grams of ALA, it was suggested we should take 250 mg of preformed DHA/EPA, which can be gotten from fish or algae.

Fish is a tough one. On one hand, fish has preformed DHA and EPA, but, on the other hand, our oceans have become so polluted that seafood may also contain various pollutants, including dioxins, PCBs, pesticides like DDT, flame-retardant chemicals, and heavy metals, including mercury, lead, and cadmium, all of which can negatively affect human health. Dietary exposure to PCBs, for example, is associated with increased risk of stroke in general and an almost three times higher risk of hemorrhagic stroke. Unless you live next to a toxic waste dump, the major  source of exposure to PCBs is fish consumption. Salmon may be the worst.

This may explain why studies in the United States have shown that just a single serving of fish a week may significantly increase one’s risk of diabetes, emphasizing that even levels of these pollutants once considered safe may “completely counteract the potential benefits of [the omega-3] fatty acids and other nutrients present in fish,” and lead to the type of metabolic disturbances that often precede type 2 diabetes. Now, one could get their daily 250 mg of preformed DHA/EPA from algae oil rather than fish oil. Algae oil is free of toxic contaminants because it is manufactured without pollutant exposure. 

Then, one could get the best of both worlds: the beneficial nutrients without the harmful contaminants. However, it was demonstrated recently that these long-chain omega-3s don’t seem to help with preventing or treating heart disease after all. Since that was the main reason we thought people should get that extra 250 mg of preformed EPA and DHA, why do I still recommend following the guidelines in my Optimum Nutrition Recommendations? Because the recommendations were not just based on heart health, but brain health, as well. See my video Should We Take DHA Supplements to Boost Brain Function?.


Other omega-3 videos include:

If the no-heart-benefit surprised you, check out Is Fish Oil Just Snake Oil?.

Surprised by the link with diabetes and want to learn more? See:

Food Sources of PCB Chemical Pollutants has more on PCBs, and here are additional videos on other pollutants:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: