The UK Food Standards Agency has reiterated its advice to pregnant and breastfeeding women regarding fish intake in a bid to protect against what it called "the small risk from mercury".
The advice, which applies also to women who intend to become pregnant, is that consumption of tuna be limited to no more than two medium-size cans or one fresh tuna steak per week, and that shark, swordfish and marlin be avoided altogether.
Dr Andrew Wadge, acting director of food safety at the Food Standards Agency, said: "It is unlikely that many pregnant or breastfeeding women eat more than the recommended amounts of these fish every week. But for any that currently do, it would be a sensible precaution to change their diets slightly. This will help protect the unborn child and the developing breastfed baby. When planning to have a baby and whilst pregnant or breastfeeding, women do need to take particular care of their health and that of their baby."
This new advice on tuna does not apply to children or any other adults, the FSA said, but infants and children under 16 are still advised to avoid eating shark, swordfish and marlin. These three fish can have levels of mercury approximately five to seven times higher than that of canned tuna and two to four times higher than that of fresh tuna.
A survey of fish carried out by the FSA in 2002 revealed relatively high levels of mercury in some types of large predatory fish, and the latest FSA advice has been issued following an extensive review by the independent Committee on Toxicity (COT) on the possible risks.
During this review, the COT compared levels of mercury found in fish against World Health Organisation safety guidelines for weekly intake of mercury (3.3 micrograms per kilogram of bodyweight per week). While the COT felt this limit was adequate to protect the general population, it was concerned that it may not be sufficiently protective for the developing foetus and breast-feeding baby because of the possible effects on the central nervous system. The COT concluded that, for these groups only, a more precautionary approach was required, and recommended a maximum intake of 0.7µg/kg bw/week.
The new safety guideline for pregnant and breastfeeding women and women intending to become pregnant is almost five times lower than that for the general population.
But the agency was quick to point out the continued benefits of fish consumption in general, and urged consumers not to panic about possible mercury intake. "Fish remains an important part of a balanced diet. It is a good source of high quality protein and other nutrients; it is low in fat and oily fish can help prevent death from heart attack. Because of these benefits, fish is also an important part of a balanced diet for pregnant women," the FSA said.
The Food Standards Agency's general advice on fish consumption is to eat two portions of fish a week, one of which should be oily, as part of a balanced and varied diet. This advice is based on findings that this level of fish consumption resulted in a significant reduction in the risk of heart attacks. On average, people in the UK eat only three-quarters of a portion of white fish and one quarter of a portion of oily fish a week.