Diet of ocean fish harmful to children: study
Too much ocean fish could lead to severe learning and behavioural disorders among young children, medical experts have found.
The findings, published by the Medical Journal of Australia yesterday, involved a study conducted on children under six who had a regular diet of large, predatory fish.
It was found that while eating small fish two to three times a week could be beneficial to the development of the heart and nervous system, a regular intake of large fish can lead to mercury poisoning.
Excess mercury in a child's system can result in retarded development and neurological problems including aggressive and repressive behaviour, delayed speech and autism.
The Sydney Morning Herald reported that three ethnic Chinese children, who had eaten fish up to eight times a week, were showing mercury levels in blood two to seven times the maximum safe level. They had been weaned on fish congee.
A two-year-old boy displayed aggressive behaviour, a three-year-old had delayed speech and certain autistic traits, and a 15-month-old boy had three times the normal level of mercury in his blood.
Tse Hung-hing, a Hong Kong Medical Association member who specialises in paediatrics, said eating large fish too often was undesirable for both adults and children.
'It's difficult to set the limits for fish intake,' Dr Tse said.
'It depends on the mercury level of the fish. Freshwater fish commonly used for congee or porridge in Hong Kong are low in mercury content.
'If a child is not fed more than 500 grams of fish per week, it will normally be very safe. But if you are talking about fish with a higher mercury content like tuna, swordfish and marlin then it will of course be different.'
He added that fetuses were more vulnerable to mercury, but the tolerance did not differ remarkably between children and adults.
Other fish that are high in mercury include shark, catfish, broadbill and orange roughy. Those low in mercury include bream, rainbow trout, ocean trout, flathead, kingfish, whiting and salmon.
The effects of fish intake on the health of children and fetuses have been contested.
The US Food and Drug Administration and Environmental Protection Agency recommended that pregnant women restrict consumption of seafood because of the accumulated chemicals. But British research showed that eating fish during pregnancy boosted the cognitive development of the fetus, outweighing the risk of toxins.