Does a diet rich in fish and fish oils safeguard you against a heart attack? Not if you've never had one, it seems, but it could protect you against getting another one.
Scientists have been puzzling about the effects of fish on the heart ever since researchers discovered a low incidence of heart problems among the people of Japan and Greenland, who both have a diet rich in fish. They believe it is the omega-3 fatty acids in fish which have such a beneficial effect.
Some early research indicated that a fish diet could protect against a heart attack, but a major new study from Harvard suggests this is not the case, even if you eat up to six fish meals a week.
The new study, among 44,895 men aged between 40 and 75 who had no history of heart disease, found that the group which had fish just once a month were no worse off than those who had fish six times a week.
But it seems a fish diet can have enormous benefits for those who have already suffered a heart attack, had angioplasty, or have high blood pressure.
Analysis of existing data, carried out by the University College London Medical School, has concluded that fish oil is likely to help heart sufferers. One study carried out in 1989 found that 300g a week of polyunsaturated fatty acids reduced the mortality rate from heart attack by one-third among previous sufferers (NEJM, April 13, 1995, and the BMJ, April 1, 1995).
Today's preschool children are taller and heavier than their 1960s counterparts, despite eating too much of the "wrong" food. A British government study found that 70 per cent ate "junk" food, while just 39 per cent ate leafy green vegetables, and less than a quarter ate raw vegetables and salad.