Omega-3s – the fatty acids found in fish, nuts and some plants – are considered important for our cognitive and mental health.
Many mothers-to-be also dutifully take omega-3s via fish oil supplements in the belief that it will help the brain development of their baby-to-be.
![Eating whole fish is better than taking supplements.](/web/20170328053514im_/http://www.smh.com.au/content/dam/images/g/q/w/o/4/f/image.related.articleLeadwide.620x349.gv77pz.png/1490589290317.jpg)
A new study has found that pregnant women who take fish oil supplements do not give birth to brighter babies.
"The sale of prenatal supplements with docosahexaenoic acid (DHA) continues to increase, despite little evidence of benefit to offspring neurodevelopment," wrote the study's authors from the South Australian Health and Medical Research Institute and the University of Adelaide.
They randomly assigned a group of 259 pregnant women a daily DHA supplement of 800mg and 284 pregnant women with a daily placebo during the second half of their pregnancy and followed up with the children until they were seven.
When the children of the participants were 18 months old there were "no group differences in cognitive, language, and motor development". At four-years-old there was no difference in general intelligence, language, and executive functioning. There was however "a possible negative effect" on parent-rated behaviour.
When 85 per cent of the children were assessed at the seven year follow-up – the earliest age at which adult performance can be indicated – they once again found no significant differences in intelligence and academic performance. And once again, they found that the parents of the prenatal DHA group reported worse behaviour.
"This randomised clinical trial provides strong evidence for the lack of benefit of prenatal DHA supplementation on IQ at 7 years and cognition at 18 months and 4 years, despite higher numbers of preterm children in the control group," the authors said in the paper published in the Journal of the American Medical Association.
They added that the "small but consistent negative effects" in the DHA group may be down to chance.
"The differences in behaviour, executive dysfunction and perceptual reasoning are all likely due to chance, rather than an effect of the supplements," said co-author Dr Jacqueline Gould.
She added that their advice, based on their research, is to eat a variety of wholefoods.
"If you have a typical normal pregnancy and eat a varied diet, then DHA supplements are unlikely to have any benefits for your child's brain development," Gould said.
"There is ongoing research to investigate whether fish oil may increase the length of pregnancy, and hence reduce the risk of giving birth too soon, and whether fish oil may prevent a child from developing allergies."
Dietitian Melanie McGrice says that it's also worth keeping in mind that fish oil supplements are not the same as eating whole fish, which contains other nutrients that help the body to better metabolise DHA.
"I believe that the key thing to focus on with this study is that it found that fish oil supplements didn't improve intelligence – but that doesn't mean that eating fish won't make the difference," McGrice says.
She points to one recent study which found the children of mothers who ate fatty fish while they were pregnant had higher IQs.
"Once again, it's an important reminder that we should be focusing on eating a nutritious diet, as opposed to relying on supplements," McGrice says.
"Mums-to-be need to be looking for omega 3-rich, low mercury fish such as salmon, whiting, hake and barramundi, and ensuring that it is well cooked to minimise the risk of listeria toxicity. Tinned tuna is a safe, easy and nutritious options for busy mums-to-be to consume throughout their pregnancies."
Fish, plants, and nut oils are the primary dietary sources of omega-3 fatty acids. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found in cold-water fish such as salmon, mackerel, halibut, sardines, tuna, and herring. ALA is found in flax seeds, flaxseed oil, canola (rapeseed) oil, soybeans, soybean oil, pumpkin seeds, pumpkin seed oil, purslane, perilla seed oil, walnuts, and walnut oil.
The health effects of omega-3 fatty acids come mostly from EPA and DHA. ALA from flax and other vegetarian sources needs to be converted in the body to EPA and DHA. However, many people's bodies do not make these conversions very effectively.