EVEN the most brazen snake-oil salesman might blush at trying to sell the public on a pill to ease aches and pains, strengthen bones, slow down cancer and prevent diseases as varied as Type 1 diabetes, multiple sclerosis and schizophrenia.
But these claims aren't the frothy hyperbole of a sideshow huckster. A growing number of serious scientists are quite willing to speculate that a single compound may be able to accomplish all of these feats -- and possibly more. They're not talking about a new miracle drug, but a common nutrient: vitamin D, "the sunshine vitamin."
Once seen as merely a defense against rickets, vitamin D has in recent years gained recognition as a major force that acts throughout the body. It improves absorption of calcium, controls the growth of cells (both healthy and cancerous), strengthens the immune system and seems to rein in overzealous immune system cells that cause diseases such as rheumatoid arthritis and multiple sclerosis.
Much of vitamin D's potential is still just that: potential. But at this moment, to some scientists the potential looks huge. "Even if two-thirds of these things don't pan out, it's still a blockbuster," says Dr. Robert Heaney, a professor of medicine at Creighton University in Omaha, who specializes in osteoporosis.
As excitement about vitamin D grows, so does the concern that many people may not be getting enough. In March, an article in the journal Mayo Clinic Proceedings called vitamin D deficiency "a largely unrecognized epidemic in many populations worldwide."
Heaney and many other researchers believe the Food and Drug Administration should consider radically increasing the suggested daily dietary intake of the vitamin, which is currently set at 200 international units (IU) for anyone younger than 51, 400 IU for people 51 to 70, and 600 IU for those 71 and older.
They cite studies such as one published earlier this year that found that cancer deaths were especially common in men with low levels of vitamin D, and a series of studies showing that high levels of vitamin D improved strength and prevented falls in elderly people.
"The daily allowances for vitamin D are outdated," says Anthony Norman, a professor of biochemistry at UC Riverside. "I would recommend 1,000 IU per day for all ages, with a maximum of 2,000 IU. I'm considering taking 2,000 IU myself." And, he adds, current evidence suggests that even 10,000 IU -- overkill by anyone's standards -- would probably be safe.
"I'm 99% sure that vitamin D deficiency is becoming more common," says Dr. Walter Willett, a professor of epidemiology and nutrition at Harvard University who has conducted several studies on the health effects of vitamin D. In one of them, he and his colleagues estimated that an extra 1,500 IU of vitamin D each day could reduce the risk of deadly cancers of the digestive system by 45%.
Willett believes that more than 1 billion people on the planet -- including about two-thirds of whites and almost all blacks in America -- don't have enough for optimal health. In recent years, shortages of the compound have even led to a resurgence of rickets, a childhood bone deformity, especially among dark-skinned babies who are exclusively breast-fed.
Growing body of research
Vitamin D is the only vitamin that the human body can make on its own, with a little help from rays of ultraviolet B light. On a sunny day, a fair-skinned person can make 10,000 to 20,000 IU in 15 minutes or less. Vitamin D is also available in fatty fishes such as salmon and mackerel and in fortified foods such as milk, orange juice and cereals.
The vitamin was discovered about 80 years ago, when doctors realized that both cod liver oil and sunlight could cure the rickets plaguing many poor children in northern cities. The race was on to find the common thread. The German organic chemist Adolf Windaus won that race -- and the Nobel Prize -- by isolating the vitamin in 1926.
For decades, nobody suspected that vitamin D could do anything other than strengthen bones. But today it's clear that D is a powerful agent with wide-ranging effects. Unlike other vitamins, which act like cogs to aid specific enzymes in the body, vitamin D cycles through the liver and kidneys to turn into a potent steroid hormone in the same chemical class as estrogen and cortisol.
Whatever messages vitamin D carries, the whole body seems to listen. Scientists have found receptors that respond to it in just about every type of human cell, from brain to bones. The hormone can also switch at least 200 genes on and off.
Researchers aren't even close to understanding all of its effects, but what they've seen so far has them buzzing. At a vitamin D scientific workshop in April, 37 speakers from around the world talked of their work, and "everybody there was excited," Norman says.