Older people who eat an orange a day during the winter can reduce their risks of a heart attack by 10 per cent. An orange contains about 60 mg of the vitamin, which scientists reckon is enough to build up body stores to their summer levels.

Vitamin C may also protect against respiratory disease, which, with heart disease, account for the 40,000 additional deaths an increase of 30 per cent that occur in Britain in the winter.

Researchers from Addenbrooke's Hospital in Cambridge, England, have discovered that an extra 60 mg of vitamin C a day could reduce levels of the clotting agent fibrinogen in the blood, so reducing the risk of heart disease by 10 per cent. They think it could also offer protection against respiratory failure, although they did not test for this.

Their findings go some way to explaining why more older people die in the winter than the summer. Risk factors for heart disease tend to increase in the winter months anyway, but the situation is worsened because people's average stores of vitamin C tend to fall during the colder seasons as diets change.

The average daily intake of vitamin C among the study group during the summer was 90 mg, falling to 65 mg in the winter, possibly because there was a smaller selection of fruits and vegetables available.

The study was based on a one-year report on 96 men and women, aged between 65 and 74, living in the Cambridge area. Although many earlier studies had shown a link between heart disease and the antioxidants, which include vitamin C along with beta carotene, vitamin E and selenium, the Cambridge study is one of the first to scientifically measure the levels of vitamin C in the blood (BMJ, June 17, 1995).