I know you work hard to make the best lifestyle choices
so you can improve your health, destiny, and longevity.
And there’s lots of information out there on how to do just that.
So where do you start? Well – we start with the facts.
Welcome to the Nutrition Facts Podcast – I’m your host Dr. Michael Greger.
My job is to bring you the latest peer- reviewed nutrition and health research
and share it with you here.
Today we look at the long chain omega 3 fatty acid –
DHA, that plays an important role
in supporting pregnant and breast-feeding women.
In our first story,
we discover how DHA improves the development of infants.
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 did not,
based on data like this where infants given control formula without DHA
didn't do as well as those given DHA-fortified formula.
Neither did as well as the breast-fed infants, who serve as the gold standard.
But 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 however much is naturally found in breast milk.
However, the DHA level in breast milk is extremely variable,
depending on what the mom is eating.
For example, there's all these healthy populations that don't eat any seafood,
and have much lower levels in their milk and they seems fine,
so that 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 per day of DHA during pregnancy.
Of course, this isn't as simple as encouraging women to eat more fish
because of the toxic pollutants such as mercury, such that for most fish,
such as tuna,
the brain damage caused by the mercury would exceed the benefit from the DHA.
And some pollutants like PCBs can get stuck in our bodies for decades
and 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 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 get it from,
and 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.
But until recently, we thought everyone should take these long chain omega 3's
for their heart. But the balance of evidence is now such
that doctors should no longer be recommending fish oil intake
or fish consumption solely for prevention of coronary heart disease.
But what about for expectant and breastfeeding mothers?
What's the latest science show?
Put all the studies together and it turns out adding DHA to formula
does not appear to help infant cognition after all, similar to other
recent compilations of evidence that showed no significant benefit.
In fact, at least four meta-analyses or systematic reviews
have reached a similar conclusion.
Now these were mostly based on a standard series of measurements
known as the Bayley Scales for Infant Development.
Maybe if other tests were used there'd be different results?
But so far, no luck.
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 benefits for 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 that showed benefit had some problems.
And so we really don't know at this point.
But hey, if all the studies so far show either nothing or benefit,
why not just take them to err on the side of caution?
Yeah, no demonstrable clear and consistent benefits,
but there's 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 800 mg of DHA a day
during pregnancy, infant girls exposed to the higher-dose DHA in the womb
had lower language scores and were more likely to have
delayed language development than girls from women in the control group.
So the absence of clear positive effects,
along with the possible presence of negative effects in the children,
raised the question whether DHA supplementation is justifiable.
But it was a really large dose, suggesting that there may be an optimal DHA level,
below and above which DHA might be detrimental to the developing brain.
So maybe too much is detrimental. What about too little?
I'll cover that next.
A systematic review of randomized controlled trials
of DHA supplementation of pregnant and breast-feeding women
failed to find any clear and consistent short or long-term benefit
for psychomotor, mental, visual or physical development.
Maybe DHA supplementation during pregnancy has no effect
because the body isn't stupid and 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 maybe women
with very low intakes would benefit from DHA supplementation.
Well, first it's interesting to note that even by 1978
researchers were suggesting plant-based diets as the diet of choice
in the treatment of our number one killer.
But babies breastfed by vegan moms
have significantly less DHA in their bloodstream 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 children are normal,
as long as they're getting their B12.
No evidence that neural or intellectual functions are impaired.
In fact the two studies we have on vegetarian kids
showed that they had higher IQ's, though that may have been
because their parents tended to be better educated.
But 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.
You can see vegans had 14, vegetarians 30, omnivores 37.
Now just because babies breastfed by vegan moms
have significantly lower DHA levels in the blood
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 intakes of DHA doesn't necessarily equate
with fetal DHA inadequacy,
but this new data suggests that some infants may not be getting enough
and could benefit from their moms supplementing.
And so I recommend pregnant and breastfeeding women
on plant-based diets do 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.
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please go to the Nutrition Facts Podcast landing page.
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