Fish oil supplements that contain DHA (docosahexaenoic acid, an omega-3 fatty acid) are marketed to pregnant women as a way to support brain development. After all, who doesn’t want their child to be smart?
However most clinical tests that have examined the impact of DHA on brain development are underpowered – that is, they do not contain enough subjects to draw reasonable conclusions – or have methodological limitations.
A large and robust trial of 500 mother-child pairs from South Australia has just been completed. The women received a high dose of DHA or a vegetable oil placebo throughout the second half of pregnancy. Comprehensive assessments of the child’s intelligence, language, behavior and executive functions (high-level complex skills) at 18 months, 4 years and now 7 years have consistently shown no benefit from fish oil supplements.
It took over 10 trials of DHA supplements during pregnancy with over 5,000 women to test the initial claims that fish oil can make children smarter, but we finally have an answer: if you have a normal pregnancy and a varied diet, then they don’t.
How did the focus on fish oils begin?
The link between fish oil and the brain began when it was discovered that the brain is rich in the omega-3 fatty acid called DHA. Fish and fish oil are rich in DHA, although smaller amounts can also be found in egg yolk and the lean tissues of red meat. Once consumed, DHA is absorbed into the bloodstream for distribution throughout the body. The more DHA we consume, the higher the level of DHA in our blood.
This is important for the unborn baby, which receives DHA from its mother’s blood. DHA is transferred from mother to baby through the placenta. Large amounts of DHA go to the baby’s brain, especially in the last trimester when the brain is going through a rapid growth spurt. DHA intake during this important period of brain development is crucial. Preterm infants lack placental supply of DHA and have lower levels in their brain.
The idea that fish during pregnancy will make children smarter was backed by a 2007 observational study of seafood consumption at 32 weeks of pregnancy in over 5,000 UK women. Children up to three and a half years old were more likely to have lower motor, social and communication skill scores if mothers ate fewer than three servings of seafood per week. There was no association between seafood consumption and measured IQ at age 8, but women who ate less than three servings of seafood per week were more likely to have a child with an IQ score lower verbal.
Many have interpreted these results as showing the benefits of eating fish during pregnancy for the child’s brain development. Supplement makers have used this discovery to market the benefits of fish oil, leading the general public to believe that DHA supplements for pregnant women are beneficial for brain development.
Experts were less convinced. Observational studies like this do not prove that eating fish will make a child smarter due to confounding factors that also influence child development. In this study, for example, women who ate fewer than three servings of seafood per week had lower levels of education, were more likely to be smokers, and were less likely to have breastfed their child.
Only randomized controlled trials can prove cause and effect, because all confounders are randomized equally between treatment and placebo groups. Our trial was the first with a large sample size and consistent assessments at important developmental times with excellent follow-up rates.
Do supplements promote brain development during pregnancy?
Fish oil is not the only supplement once believed to improve child brain development that has now been disproved due to lack of scientific evidence. Prenatal the iron and iodine were both once thought to be beneficial, but have limited effectiveness when the mother does not lack these nutrients. Too few studies have looked zinc Where multivitamins during pregnancy for babies’ brains.
As with the fish oil studies, most of the women in these trials had a varied diet and are unlikely to be deficient in these nutrients or benefit from excess intake.
Certain groups of women, such as vegans or vegetarians, may benefit from other supplements.
Fish oils can help in other ways
Although DHA supplements won’t make your baby smarter, there are suggestions of other possible benefits.
Several trials of DHA-rich fish oil during pregnancy have found a slight increase duration of pregnancy in women taking the supplement. This led to small decreases in the number of children born very preterm in these studies. Although more studies are needed to prove this effect, DHA is one of the only interventions that has been identified as having the potential to prevent preterm birth.
DHA is known to have a role in the immune response to inflammation and infection. A exam DHA supplements during pregnancy revealed that children at high risk of developing an allergy, for example if they have an allergic close family member, may be less likely to develop an allergy.
It should be noted here that the dose of DHA used in these trials showing possible benefits is typically double to quadruple the dose in commercially available prenatal supplements. Further work is needed to prove these effects.
A healthy and varied diet is the best way to ensure that all nutrient needs are met. There is a general consensus that fish should be part of a healthy diet during pregnancy; it is an excellent source of DHA and other omega-3 fatty acids, protein, and a variety of vitamins and minerals.
However, some fish species (predators) such as shark and swordfish contain mercury, which is likely to be harmful to an unborn baby. Consumption should be limited at safe species for pregnant women to eat, such as canned salmon and light tuna or skipjack tuna (not albacore).