Eating two portions of fish a week while pregnant halves the risk of ADHD – but make sure it's haddock rather than tuna
Children whose mothers ate two portions a week had a 60 per cent lower risk of developing symptoms
But women advised to avoid eating too much oily fish
16:23 GMT, 9 October 2012
The amount of fish a woman eats while pregnant may affect her child's chances of developing attention-deficit/hyperactivity disorder (ADHD).
Eating fish twice a week was linked to about a 60 per cent lower risk of a child developing certain ADHD-like symptoms, according to research from the Boston University School of Public Health.
But the type of fish eaten is key.
Eating for two: Pregnant women who consume fish twice a week reduce their child's risk of ADHD by around 60 per cent
Elevated mercury levels, which can occur from eating certain types of fish, such as tuna and swordfish, were also tied to a higher risk of developing ADHD symptoms such as a short attention span, restlessness or being easily distracted.
'The really important message is to eat fish,' said assistant professor Sharon Sagiv, the study's lead author.
She added that pregnant women should avoid 'big' fish, such as tuna and swordfish, which typically contain the most mercury. Instead, they should opt for haddock or salmon.
The research was published in the Archives of Pediatrics & Adolescent Medicine.
Past studies looking at the link between mercury and ADHD – a condition estimated to affect up to 5 per cent of school-aged children – have produced conflicting results.
No sushi: Oily fish such as tuna and salmon should be eaten sparingly, as they contain higher levels of pollutants than white fish such as haddock
ADHD is the most common behavioural disorder in the UK.
Most children are diagnosed between the ages of three to seven, with boys more commonly affected.
Many people with ADHD also have learning difficulties and sleep disorders.
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 behaviors.
But 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.
WHICH FISH ARE SAFE TO EAT DURING PREGNANCY
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.
Shark, swordfish and marlin should all
be avoided as they contain high levels of mercury, which can damage a
baby’s developing nervous system.
Tuna should be limited to two steaks or four medium-sized cans as it also contains high levels of mercury.
There is no limit on other types of white and non-oily fish, such as cod, haddock or plaice.
Source: NHS Choices