Eating up to four portions of oily fish a week poses little risk of a build up of toxins in the body and gives a major boost to a healthy heart, British government food experts said on Thursday.

The new guidelines, issued after an investigation lasting nearly a year, quadruples the amount of oily fish like mackerel, tuna and salmon that people had previously been advised to eat each week.

“Eating just one portion of oily fish a week has clear cut health benefits,” Food Standards Agency (FSA) chief John Krebs told reporters.

“This extensive review of the scientific evidence has reduced the uncertainty about how much oily fish people can safely eat without the benefits being outweighed by the risks,” he added.

The FSA said its new advice to eat up to four portions of oily fish a week applied to men, boys and women past child-bearing age.

Girls and women likely to become pregnant at some stage should limit their intake to two portions a week to avoid any possible build up in their bodies of toxins than might be passed on in the womb, it added.

It is well established that including oily fish in the diet helps reduce the risk of heart disease-one of the world’s biggest killers.

In Britain alone, 117,500 people died of heart disease in 2002, the FSA said.

On average Britons eat just one third of a portion of oily fish each week, with the vast majority completely excluding it from their diets.

There have been several scares about the levels of toxins such as dioxins and PCBs in fish in recent years. Both chemicals are carcinogens and persistent in the environment.

Earlier this year one study into farmed salmon said the levels of harmful chemicals in the fish were so high that they should only be eaten very sparingly. But Krebs said that Thursday’s eating recommendations included farmed salmon.

“The conclusions were based on average levels of dioxins and PCBs in oily fish,” he said. “Some species have lower levels and some have higher and at the levels found in farmed salmon, they would fall within the guidelines.”