Author: Dr. Stephen Chaney
Is taking a prenatal DHA supplement wise for brain health?
There are lots of reasons to think that DHA supplementation may be important for healthy brain development.
- DHA is a major component of the myelin sheath that coats every neuron in the brain.
- Just as the plastic coating on copper wire allows it to conduct an electrical current, the myelin sheath allows neurons to conduct nerve impulses from one end of the neuron to the other. In short, the myelin sheath is absolutely essential for brain function.
- Unlike many of the other components of the myelin sheath, the body cannot make DHA. It must be provided by the diet.
- Recent studies have suggested that most women in the United States and Canada do not get sufficient amounts of the omega-3s EPA and DHA in their diet.
- Animal studies show that DHA deficiency during pregnancy interferes with normal brain and eye development.
With all that circumstantial evidence, it would seem obvious that a prenatal DHA supplement would be important for healthy brain development in infants and children. However, clinical studies have been all over the map.
Some studies have reported that DHA supplementation during pregnancy improves cognition, attention span, behavior or reading skills in both infants and children. Other studies have shown no effect of DHA supplementation on those parameters. There is no consensus on this very important question.
Thus, when I saw a recent study titled “Prenatal Supplementation with DHA Improves Attention At 5 Years Of Age: A Randomized Controlled Trial” (U Ramakrishnan et al, American Journal of Clinical Nutrition, doi: 10.3945/ajcn.114.101071, 2016), I decided to Investigate.
Does Taking a Prenatal DHA Supplement Improve Attention Span?
In this study 1094 Mexican women were randomly assigned to receive either 400 mg of DHA or a placebo containing corn and soy oil starting in the second trimester of pregnancy (a time at which myelination and brain development begins) until delivery. Of the women enrolled in the study, 973 of them gave birth to healthy babies.
The investigators were able to follow up with 797 (82%) of those children at age 5 and conducted tests to measure overall cognitive function, behavior, and attention span.
- There were no differences in overall cognitive development or behavior between the two groups.
- The children from mothers who supplemented with DHA performed significantly better in tests of attention span. They were much less likely to be distracted by external stimuli than the children from mothers not supplementing with DHA.
- In short, this study suggested that supplementation with DHA during pregnancy produced children who were less likely to suffer from attention deficit disorders at age 5.
This study had a number of strengths:
- It was a fairly large study (797 children).
- Supplementation was with pure DHA rather than with a mixture of EPA, DHA, and other omega-3 fatty acids.
- The population was from an urban area of Mexico where omega-3 intake is generally low, so it was likely that many of the women were DHA-deficient at the beginning of the study.
However, it also had some glaring weaknesses:
- The DHA status of the women was not measured either at baseline or after supplementation.
- The quality of the child’s learning environment was not measured.
In short, the study was neither better or worse than the many other published studies.
Why Is There So Much Confusion?
To try and clear up the confusion I have also analyzed many of the other published studies in this field. There were things not to like about every study, but there was no obvious reason why some studies showed a positive effect of DHA supplementation and others failed to see any benefit. This is not unusual for human nutrition clinical studies, but it is frustrating.
However, when you look at the totality of the studies in this field there is one obvious reason why there is so much confusion. There is no uniformity in experimental design. No two studies are alike.
The published studies differ in:
- The composition of omega-3s. Some studies are done with pure DHA. Others with mixtures of EPA and DHA and with varying ratios of EPA to DHA.
- The amount of DHA. Studies range from 100 mg/day to 800 mg/day.
- When the DHA is given. Some studies give the DHA to the pregnant mothers. Others give DHA to infants or to children of various ages.
Even worse, most of the published studies to date have not measured omega-3 status prior to supplementation, nor have they documented an improvement in omega-3 status with supplementation. Obviously, DHA supplementation is most likely to be beneficial for individuals who were DHA-deficient at the beginning of the study.
Until there is some uniformity in experimental design and DHA status is routinely measured, it is likely that the confusion will continue and this important question will remain unanswered.
Should Pregnant Women Take a Prenatal DHA Supplement?
If we were to assume that most American women were getting enough omega-3s in their diet, and the consequences of DHA deficiency were relatively minor, this would be merely an academic discussion. We could afford to wait years until scientists were able to come to a consensus.
However, neither of those assumptions are true:
- One recent study reported that the United States and Canada rated last in the world with respect to omega-3 intake.
- Another study reported that 75% of Canadian women were not getting enough omega-3s during pregnancy. Other studies suggest that the situation is very similar in the United States.
- If any of the reported consequences (short attention span, cognitive deficits, and behavioral problems) of DHA-deficiency during pregnancy and childhood are true and they are preventable with DHA supplementation, this information is of vital importance to every woman during her child bearing years.
In short, inadequate DHA intake is so widespread and the possible consequences of DHA deficiency during pregnancy are so important that, in my opinion, a prenatal DHA supplement only makes sense. Pregnant women can’t afford to wait until we are absolutely sure that DHA supplementation is essential.
The only caveat to this recommendation is to make sure that the DHA you are getting is pure. Our oceans are increasingly polluted. Many fish and some fish oil supplements are contaminated with heavy metals and/or PCBs. Only use omega-3 and/or DHA supplements from manufacturers that use very stringent quality controls to assure their products are pure.
The Bottom Line
- A recent study has reported that DHA supplementation during pregnancy improves attention span in children at age 5.
- Unfortunately, there is no consensus in this field. Some studies have come to similar conclusions while others have seen no effect of DHA supplementation during pregnancy.
- If we were to assume that omega-3 deficiency was rare in this country and the consequences of DHA deficiency during pregnancy were inconsequential, this would be an academic discussion. Pregnant women could wait for scientists to reach consensus before deciding whether or not to supplement with DHA. However, neither of those studies are true.
- Studies show that most women in the US and Canada do not get adequate omega-3s during pregnancy.
- If any of the reported consequences of DHA deficiency during pregnancy are true and they are preventable with DHA supplementation, this information is of vital importance to every woman during her pregnancy.
- In short, inadequate DHA intake is so widespread and the possible consequences of DHA deficiency during pregnancy are so important that, in my opinion, DHA supplementation during pregnancy only makes sense. Pregnant women can’t afford to wait until we are absolutely sure that DHA supplementation is essential.
- The only caveat to this recommendation is to make sure that the DHA you are getting is pure. Our oceans are increasingly polluted. Many fish and some fish oil supplements are contaminated with heavy metals and/or PCBs. Only use omega-3 and/or DHA supplements from manufacturers that use very stringent quality controls to assure their products are pure.
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.