So can sunshine beat heart disease?
This Easter, it's not over-indulging in chocolate you should be worrying about, but your lack of exposure to the sun over the past six months.
All through winter, your vitamin D stores will have been declining, and by now you will have a fraction of what you need — not just for strong bones but to fight off a range of diseases, including cancer, heart disease and infections.
Last month, a study of 7,500 men and women found that most don't have enough vitamin D in their bloodstream for at least six months of the year. Although our bodies absorb some vitamin D from the food we eat, it can't absorb enough— the body has to manufacture the rest through sunlight.
Fewer UVB rays reach the ground during the winter months, and less so the further north you go. The Scots, according to the new study, are twice as likely to suffer from dangerously low levels of vitamin D. Researchers have suggested that by ensuring we get adequate amounts, breast, prostate and colon cancer rates would be reduced by more than 50 per cent. Other research has found that improved intake would help to prevent osteoporosis.
Inadequate levels of the vitamin have also been linked to depression and weight gain.
What's so controversial about this research, conducted at some of the world's top scientific centres, is that it suggests the current recommended daily amount for vitamin D is way too low. The official advice is that we need between 200 and 400 iu (international units of concentration) a day, some of which we can get from food — notably fatty fish and cod liver oil, but also lard, butter and egg yolk — and the rest from sunlight.
It's long been known that people in some immigrant groups are more likely to be deficient, but it now appears that most white middle-aged people, the ones thought to be fine, are seriously lacking in vitamin. Over 2,000 iu, according to some sources, puts you at risk of absorbing too much calcium, leading to liver, kidney and heart damage. Other side-effects of overdosing includes increased thirst, nausea and vomiting.
However, one of the authors of the recent study linking vitamin D and flu, takes 5,000iu daily in the winter, and advises people to take 2,000 iu for each kilo of their body weight daily for three days at the first sign of infection.
There are other examples of people who have taken large doses with no ill-effect. For instance, an American study of wheelchair-bound patients with severe weakness and fatigue, who were given very high doses totalling 50,000 iu a week. They suffered no problems and were walking after six weeks. Another described how a group of adolescents with a severe deficiency were given single monthly doses of 100,000 iu with no ill effects.
As yet, it's too early to say who is right about all of this; the one thing everyone agrees on is that these new ideas about vitamin D need further testing. So it is probably too early to start going for mega-doses of 10,000 iu. But modern-day living does seem designed to reduce our vitamin D intake to a minimum.
We're Dracula-like when it comes to sunlight, terrified by the fear of skin cancer into spending our days indoors, and when we do venture out, we are urged to slap on the sun block.
As for our diet, the low-fat mantra discriminates against foods with vitamin D, most of which come with high doses of fat and cholesterol. Since our food is unlikely to be fortified any time soon, should you be taking a supplement? No one can tell you for certain, but it's certainly worth making sure you get enough sun. It's time to book that holiday.