Thursday, 28 November, 2002, 00:11 GMT

Mercury is found in some marlin, swordfish and tuna

Eating certain types of fish can increase the risks of having a heart attack, a study suggests.

A team of international researchers has found a direct link between mercury and heart disease.

High levels of mercury are found in shark, swordfish, king mackerel and marlin. It is also found at lower levels in fresh or frozen tuna.

These new findings do not affect our current advice for people to try to eat fish twice a week

Belinda Linden, British Heart Foundation The researchers have suggested that people should consider eliminating fish with high mercury levels from their diet.

The UK's Food Standards Agency recently advised pregnant women and children against eating this type of fish.

There are fears that mercury can damage the nervous system of unborn infants and can increase the risks of poisoning in young children.

International study

These latest findings are based on a study of more than 1,400 men from eight European countries, including Britain, and Israel.

Researchers examined mercury levels in 724 of these men, who have had a heart attack. They did this by analysing their toenail clippings.

Levels of mercury in toenails are regarded as a reliable way of determining whether someone has had long-term exposure to the chemical.

They also examined the toenail clippings of the other men, who had no history of heart disease.

Their analysis found that mercury levels in men who had had a heart attack were 15% higher than those with no history of heart problems.

Eating fish is regarded as the main source of mercury exposure.

Their study also suggested that any of the benefits associated with eating fish may be lost if they have high mercury levels.

The Omega 3 fatty acids in fish are believed to have a protective effect on the heart.

Writing in the New England Journal of Medicine, the researchers suggested that the general public should be advised against eating fish with high levels of mercury.

"Exposure to methylmercury is currently a concern in specific high-risk groups, such as pregnant women and women of childbearing age who may become pregnant but this warning should perhaps be extended to the general adult population."

Health benefits

They added, however, that people should continue to eat other types of fish.

"A weekly intake of two to four servings of fish from a variety of species with special emphasis on fatty fish with low mercury content, such as salmon and small oceanic fish, is consistent with current advice for reducing cardiovascular risk."

The British Heart Foundation, which part-funded the study, backed that view.

"Whilst the benefits of eating fish are well known, this research confirms that this can be counteracted by mercury which the fish accumulate," said Belinda Linden, its head of medical information.

"These new findings do not affect our current advice for people to try to eat fish twice a week, including one portion of oily fish such as sardines and mackerel.

"This quantity should offer the benefits of omega-3 oils in fish while avoiding any potential harmful effects."

-- Anonymous, November 27, 2002