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:

The Best Way to Wash Fruit and Vegetables

How might we reduce our exposure to pesticide residues on fruits and vegetables? What about staying away from imported produce? Well, it turns out domestic produce may be even worse, dispelling the notion that imported fruits and vegetables pose greater potential health risks to consumers.

Buying organic dramatically reduces dietary exposure to pesticides, but it does not eliminate the potential risk. Pesticide residues are detectable in about one in ten organic crop samples, due to cross-contamination from neighboring fields, the continued presence of very persistent pesticides like DDT in the soil, and accidental or fraudulent use.

By choosing organic, one hopes to shift exposures from a range of uncertain risk to more of a range of negligible risk, but even if all we had to eat were the most pesticide-laden of conventional produce, there is a clear consensus in the scientific community that the health benefits from consuming fruits and vegetables outweigh any potential risks from pesticide residues. And, we can easily reduce whatever risk there is by rinsing our fruits and vegetables under running water.

There is, however, a plethora of products alleged by advertisers to reduce fruit and produce pesticide residues more effectively than water and touted to concerned consumers. For example, Procter & Gamble introduced a fruit and vegetable wash. As part of the introduction, T.G.I. Friday’s jumped on board bragging on their menus that the cheese and bacon puddles they call potato skins were first washed with the new product. After all, it was proclaimed proven to be 98% more effective than water in removing pesticides.

So researchers put it to the test, and it did no better than plain tap water.

Shortly thereafter, Procter & Gamble discontinued the product, but numerous others took its place claiming their vegetable washes are three, four, five, or even ten times more effective than water, to which a researcher replied, “That’s mathematically impossible.” If water removes 50%, you can’t take off ten times more than 50%. They actually found water removed up to 80% of pesticide residues like the fungicide, Captan, for example. So, for veggie washes to brag they are three, four, five, ten times better than water is indeed mathematically questionable.

Other fruit and vegetable washes have since been put to the test. Researchers compared FIT Fruit & Vegetable Wash, Organiclean, Vegi-Clean, and dishwashing soap to just rinsing in plain tap water. 196 samples of lettuce, strawberries, and tomatoes were tested, and researchers found little or no difference between just rinsing with tap water compared to any of the veggie washes (or the dish soap). They all just seemed like a waste of money. The researchers concluded that just the mechanical action of rubbing the produce under tap water seemed to do it, and that using detergents or fruit and vegetable washes do not enhance the removal of pesticide residues from produce above that of just rinsing with tap water alone.

That may not be saying much, though. Captan appears to be the exception. When plain water was tried against a half dozen other pesticides, less than half the residues were removed.

Fingernail polish works better, but the goal is to end up with a less toxic, not a more toxic tomato.

We need a straightforward, plausible, and safe method for enhanced pesticide removal. Is there anything we can add to the water to boost its pesticide-stripping abilities? Check out my video, How to Make Your Own Fruit & Vegetable Wash.

If you soak potatoes in water, between about 2% to 13% of the pesticides are removed, but a 5% acetic acid solution removes up to 100%. What’s that? Plain white vinegar. But 5% is full strength.

What about diluted vinegar?  Diluted vinegar only seemed marginally better than tap water for removing pesticide residues. Using full strength vinegar would get expensive, though. Thankfully there’s something cheaper that works even better: salt water.

A 10% salt solution appears to work as good or better than full-strength vinegar. To make a 10% salt solution, you just have to mix up about one-part salt to nine-parts water (though make sure to rinse all of the salt off before eating!).

There’s not much you can do for the pesticides in animal products, though. The top sources of some pesticides are fruits and vegetables; but for other pesticides, it’s dairy, eggs, and meat because the chemicals build up in fat. What do you do about pesticides in animal products? Hard boiling eggs appears to destroy more pesticides than scrambling, but for the pesticides that build up in the fat of fishes and chickens, cooking can sometimes increase pesticide levels that obviously can’t just wash off. In fact, washing meat, poultry, or eggs is considered one of the top ten dangerous food safety mistakes.

For more on organic foods, see:

The most important reason to wash produce is to reduce the risk of food-borne illness. Ironically, the food poisoning viruses may be found in the pesticides themselves. Check out my video Norovirus Food Poisoning from Pesticides.

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: