You're probably not getting enough vitamin D

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Ted Rhodes / Canwest News Service Archives Several authorities recommend taking from 1,000 to 5,000 mg of vitamin D daily.

In the 19th century, how were children treated who suffered from rickets due to a lack of vitamin D? If they were fortunate to live in New England, they were taken for long trips on Boston's Floating Hospital. This hospital ship exposed them to prolonged periods of sun, nature's way of producing vitamin D. Today, not many people develop rickets. But how much D do you need, when should you take it, and can it protect you from a variety of problems?

Here are some facts you should know.

Does vitamin D prevent cancer?

Dr. Jo Ann Manson, professor of medicine at the Harvard Medical School, reports strong evidence that higher blood levels of vitamin D help to protect against colon cancer. Other researchers at Creighton University, in Omaha, Neb., gave 1,200 healthy postmenopausal women 1,500 milligrams of calcium and 1,000 IU (international units) of vitamin D daily to determine if this combination decreased the risk of bone fracture. They were surprised to discover that these women were 77 per cent less likely to develop cancer, primarily breast malignancy, in the next four years.

Does D protect against infection?

Vitamin D has been labelled the "antibiotic vitamin" as studies show it spurs up the immunity system to fight infections. Dr. John Cannell, a U.S. psychiatrist, noted this interesting finding in 2005 when an epidemic of flu struck the hospital for the criminally insane in California. He said the infection spared those patients who were receiving vitamin D.

Dr. Mitsuyoshi Urashima, a professor of epidemiology in Japan, reports in the American Journal of Nutrition that school children given 1,200 IU of D were less likely to develop influenza A than children not receiving this vitamin. Flu usually strikes in the dark winter months when vitamin D levels are low. Dr. Urashima says he formerly suffered from several episodes of flu every year. Now he takes 3,000 IU of D daily and has not had a fever, sore throat or fatigue for the last two years. The Japanese study also revealed another shocking fact, that children not receiving D were six times more likely to suffer asthma attacks.

Does D prevent heart attack?

Dr. Edward Giovannucci, a researcher at the Harvard School of Public Health, reports in the Journal, Archives of Internal Medicine, that those with low levels of vitamin D were more likely to have a heart attack than those with higher levels of the vitamin. Giovannucci said that, in the past, doctors have been more concerned about the role played by vitamin D in preventing osteoporosis. But there's now evidence that low levels of vitamin D may cause subtle changes in a lot of tissues. Vitamin D, he said, may lower blood pressure, regulate inflammation in arteries and decrease calcification in coronary arteries.

A study by Dr. Thomas Wang, another Harvard researcher, showed people with low vitamin D levels had a higher risk of not only heart attack, but also of heart failure and stroke.

Does it matter when you take D?

Luckily, D is a fat-soluble vitamin, as are vitamins A, E and K. So if you take more than you need, the extra D is stored in the liver and then used as it's needed.

Does it matter how much you take?

The current recommended allowance is 200 to 600 IU. But I talked to several authorities about the amount they would recommend, and it varied from 1,000 to 5,000 IU daily.

Does where you live make any difference?

People living at a latitude above 35 degrees north, which includes all of Canada, can stand outside in the noonday sun naked from October to February and not manufacture one IU of vitamin D due to the angle of the sun's rays at that time.

Does D prevent diabetes?

Type 2 diabetes is usually due to obesity. But the risk of developing Type 1 diabetes is increased if there's a deficiency of vitamin D since it's needed in the production of insulin.

These reports show we need vitamin D, not just to promote the absorption of calcium to form strong bones. And that it's prudent to take at least 1,000 IU of D daily.

Republished from the Winnipeg Free Press print edition April 23, 2010 A23