The advice given to pregnant women over the consumption of fish rich in omega-3 fatty acids should be reconsidered after an international research project involving University of Ulster scientists suggested that polyunsaturated fatty acids in fish could actually be beneficial for child development.
This study adds to the evidence to show that specific nutrients in fish can boost brain development. Current medical advice in most countries is that pregnant women should limit their intake of fish but the most recent findings of the long term research project in the Seychelles points to a strong positive association between fish consumption and neurodevelopment.
Internationally renowned nutritionist, Professor Sean Strain, who is Director of the Northern Ireland Centre for Food and Health (NICHE) at Ulster’s Coleraine campus, is Principal Investigator of the project which is being conducted in collaboration with scientists at the University of Rochester in New York and the Seychelles Ministry of Health.
In light of their findings which are published in one of the top nutrition journals, the Journal of Nutrition, Principal Investigator, Professor Sean Strain said dietary advice to pregnant women should be reviewed.
Fish and shellfish contain high-quality protein and other essential nutrients. However, fish absorb toxic methylmercury as they feed, so the levels can be high in some predatory fish like shark, swordfish and ray.
Fish is the mainstay of the local diet in the Seychelles and on average, pregnant women there eat approximately 537 grams of fish each week, which is equivalent to about eight to nine meals which include fish.
Professor Strain, who is Professor of Human Nutrition in the School of Biomedical Sciences, said: “The benefits of eating fish as part of a well-balanced diet during pregnancy far outweigh any potential risks from methylmercury with respect to later development of the child."
Explaining the significance of the Seychelles study, Professor Strain continued:
“Seafood is an important source of omega-3 fatty acids, which are essential for optimum neural development. The Seychelles are ideal for this study as mothers there consume about 10 times more fish than mothers in the UK or US. So they are exposed to much higher levels of methylmercury.
“In addition to the high fish consumption, the Seychelles is a pristine environment with no other pollutants to affect the outcome of the study.
“We found that there were positive associations between omega-3 fatty acids - which are high in fish - and child language scores. In other words, higher omega-3 concentrations in the mother during pregnancy resulted in better language scores in the children at age 5 years.”
Professor Strain said the Seychelles study could help give an early warning of possible problems elsewhere.
Ulster nutritionists have been carrying out research in the Seychelles since 2001. In the first phase of the Nutrition study, 300 pregnant Seychellois women were recruited and 229 of their babies were assessed at 9 and 30 months of age. Researchers collected detailed information about the nutritional status of the mothers and completed almost a dozen standard assessments on language and intelligence of the children over several years.
“In a previous cohort, we found that foetal exposure to methylmercury was positively associated with developmental outcomes, specifically the Preschool Language Scale,” Professor Strain confirmed.
“Such associations suggest that methylmercury was having a beneficial effect, which of course cannot be the case as methylmercury is a well-known neurotoxin to which the developing foetus is particularly susceptible.
“Our hypothesis was that it was nutrients in fish which were confounding the association with methylmercury but we did not have maternal measures of nutrient status. The aim of this study was to investigate whether maternal PUFA status was a confounding factor in any possible associations between prenatal methylmercury exposure and developmental outcomes when the children were 5 years old.”
He continued: “In the current Nutrition Cohort we do have measures of maternal nutrition status, including the long-chain poly unsaturated fatty acids (PUFA), the n-3 or omega 3 fatty acids, which have been linked to brain development.
“At 9 months and 30 months of age, we found that maternal measures of these PUFA were positively linked with child development and at 30 months, we did find a negative adverse association with methylmercury but only when we adjusted for PUFA in our analysis."
Professor Strain said it was important that current campaigns advising limiting fish consumption during pregnancy should be based on the totality of evidence.
“We have continually found no adverse effects of methylmercury on childhood development. In fact, we have found benefits of increased exposure to fish consumption during pregnancy and positive associations with the nutrients in fish rich in polyunsaturated fatty acids and children’s language development.
“Naturally consumers and legislators are more interested in the possibility of risks than they are in the possible benefits. Perhaps it is time for the pendulum to swing more towards the beneficial effects of fish consumption during pregnancy rather than the adverse effects of fish consumption for later development of the child.”