Pregnant women have a significantly lower risk of a child developing attention-deficit/hyperactivity disorder (ADHD) if they regularly eat certain types of fish, according to new research from the Boston University School of Public Health.

Assistant Professor Sharon Sagiv, the study's lead author, explained that eating fish such as haddock or salmon is linked to to about a 60 per cent lower risk of a child developing certain ADHD-like symptoms.

She also warned against eating 'big' fish, such as tuna and swordfish as these contain high levels of mercury, which are linked to a higher risk of developing ADHD symptoms such as a short attention span, restlessness or being easily distracted.

The research, which was published in the Archives of Pediatrics & Adolescent Medicine, goes against previous studies looking at the link between mercury and ADHD, which have produced conflicting results.

ADHD is the most common behavioural disorder in the UK and is thought to affect 5% of school-aged children. Most children are diagnosed between the ages of three to seven, with boys more commonly affected. Learning difficulties and sleep disorders are common in children with this condition.

For the new study, the researchers followed 788 children born in Massachusetts between 1993 and 1998. They used hair samples taken from the mothers after delivery to test their mercury levels, and food diaries to see how much fish they had eaten.

Then, once the children were about eight years old, the researchers asked their teachers to evaluate the children's behaviour to see how many exhibited ADHD-like symptoms. After taking all of the information into account, the researchers found that one microgram of mercury per gram of a mother's hair - about eight times the average levels found in similar women's hair in another analysis - was linked to a 60 per cent increase in the risk of their child exhibiting ADHD-like behaviours. However there was no link below one microgram of mercury per gram of a mother's hair.

The children appeared to be 60 per cent less likely to exhibit impulsive or hyperactive behaviors if their mothers had eaten two or more servings of fish per week.

Current UK guidelines recommend that pregnant women eat two portions of fish a week, only one of them oily (such as salmon, fresh tuna or sardines). Oily fish contains pollutants such as dioxins and PCBs (polychlorinated biphenyls) which is why it must be eaten in moderation.

There is no limit on other types of white and non-oily fish, such as cod, haddock or plaice.

Posted 10/10/2012 by