Controlled trial finds that higher omega-3 intake during pregnancy boosts babies’ eye-brain axis
by Craig Weatherby
There’s no doubt that to ensure adequate brain and vision development, children need ample omega-3 fatty acids before and after being born.
In lab tests, animals that receive inadequate amounts of omega-3s during pregnancy and infancy suffer impaired brain and visual function and long-term deficits in the neurotransmitter systems that regulate critical mood and movement capacities.
Human studies show that one omega-3 in particular—called DHA—enhances visual, mental, and motor skill development in some premature and full-term babies fed DHA-fortified formula and are vital in early human development.
This is why, in 2001, the US FDA allowed makers of infant formulas to begin adding omega-3 DHA to infant formulas. (Questions have been raised about the quality and safety of the “package” in which the DHA in formulas is enfolded; see “Omega-Fortified Infant Formulas: Spoiling a Smart Idea?”.)
Fetuses depend on their mothers’ diets
Omega-3 fatty acids are essential dietary nutrients. Since fetuses get their DHA from their mothers’ blood, moms need ample DHA in their diets.
Pregnant and nursing women can get DHA from fish, fish oil supplements, and omega-3-rich eggs, or by converting the plant-form omega-3 called ALA into DHA.
Flax seeds and flaxseed oil are the richest ALA sources, by far. The richest food sources of ALA in American supermarkets are, in order of descending DHA content, omega-3 enriched eggs, canola oil, soybean oil, walnuts, and leafy greens.
But canola oil and soy oil have much less omega-3 fat than omega-6 fat, and Americans consume omega-6s to an unhealthful excess that risks children’s health. (See our companion article, “Common 'Omega-Imbalance' Raises Kids’ Health Risks”.)
And humans only convert about five percent of dietary ALA into DHA, making plant foods almost incapable of ensuring high blood levels of DHA in mothers, fetuses, and babies.
This low conversion rate explains why, even when pregnant women increase their intake of ALA, this does not increase blood levels of DHA in them or their fetuses (de Groot RH et al. 2004).
The estimated average DHA intake in pregnant American women is 40–120 mg per day, but varies from 20 mg per day to more than 500 mg per day. Women who eat vegan diets and take no fish oil supplements have the lowest DHA intake levels (Innis SM, Elias SL 2003).
To ensure that their fetuses get ample amounts of DHA while avoiding animal products, pregnant vegans can take supplements containing algae-derived DHA, such as the one used in the study detailed below.
New study probes vision-development effects of maternal DHA
Despite considerable research into omega-3s and child development over the past decade, some major questions remain unanswered.
These include two gaps in the data:
- How much DHA does a pregnant/nursing women need in her blood to ensure optimal development of her child?
- What is the minimum amount of dietary DHA mothers need in order to achieve developmentally optimal levels of DHA?
Sheila Innis, Ph.D., and Russell Friesen are researchers in the University of British Columbia’s Department of Pediatrics, Vancouver who’ve conducted several prior studies concerning maternal and fetal nutrition needs.
Earlier this month, they published the encouraging results of a clinical trial involving 135 pregnant women.
The expectant mothers were randomly assigned to either take an omega-3 supplement (DHA derived from algae) or a placebo capsule, daily, for the five months prior to delivery (Innis SM, Friesen RW 2008).
Most were well-educated white women in their late 20’s or early 30’s. There were no significant differences in age, ethnicity, education, family income, or any other demographic variable between the women assigned to the DHA and placebo groups.
The omega-3 supplement provided 400 mg of DHA per day (2,800 mg per week).
This is about as much DHA as you would get from eating four 3.5 oz portions of fatty fish per week (e.g., such as Salmon, Tuna, or Sablefish), or eight 3.5 oz portions per week of a leaner fish such as Halibut.
Innis and Friesen estimated that this amount of DHA that would be enough to prevent a DHA deficiency in the women’s fetuses, based on two facts:
- Fetuses accumulate about 70 mg of DHA per day during the last trimester. (A minority of a mother’s dietary DHA goes to her fetus, so the supplement needed to provide much more than 70 mg of DHA per day.)
- The International Society for the Study of Lipids and Fatty Acids recommends that pregnant women consume 300 mg of DHA per day.
All the women continued eating their regular diets, and the researchers tested the women’s blood at 16 and 36 weeks (four months and nine months) of pregnancy to measure their blood levels of DHA.
Results affirm value of omega-3-rich maternal diets
Unsurprisingly, after 36 weeks (nine months) of gestation blood levels of DHA averaged 32 percent higher among the mothers taking DHA capsules.
Two months after the babies were born, the researchers used a test called the Teller Acuity Card Procedure to gauge the infants’ ability to distinguish between lines of different widths.
At this tender age visual acuity is largely a brain function, so better performance on this type of visual discrimination test reflects a higher degree of brain development.
The Vancouver team found that the children of the women who took DHA supplements did significantly better on the visual acuity test, compared with the babies of mothers in the placebo group.
And the Canadian researchers made a key point in their conclusions: “…current dietary practices place women at risk of inadequate DHA during pregnancy.”
America’s extreme “omega-imbalance” impairs development
The standard American (and Canadian) diet provides 20-40 parts omega-6 fats (or more) to one part omega-3 fats (an average 30:1 ratio).
Most fatty acid nutrition researchers agree that the omega-6/omega-3 ratio ideal for human health is more like 2:1 or 4:1, which means that Americans should ingest 10 times less omega-6 fatty acids than most do.
Interestingly, the results of the new study also showed lower visual acuity scores among the infants born to mothers with higher blood levels of a marker for omega-6 intake (n-6 docosatetraenoic acid).
In other words, standard, “omega-imbalanced” North American diets may impair infants’ brain and vision development.
The researchers plan to follow the children’s progress through four years of age, and we will report any subsequent findings.
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