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"The daily allowances for vitamin D are outdated," says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.
Much of that excitement is centered around cancer research.
Just like nearly all healthy cells, cancer cells have vitamin
D receptors too — and when D binds, it tells those
cells to stop growing, a potentially life-saving command.
In fact, a 2005 article in the Southern Medical Journal
called vitamin D "one of the most potent inhibitors of both
normal and cancer cell growth."
This potential cancer-fighting power may help explain why
cancers of the breast, colon or prostate tend to be more
common, or more aggressive, in dark-skinned people, Norman
says. It may also, he adds, help explain why people in northern
states such as Maine or Minnesota — where summers
are short and sleeves, for most of the year, are long —
are more prone to these cancers than people in the sunny
South.
Other quirks of geography offer compelling evidence for
the importance of vitamin D, says Dr. Michael Holick, a
professor of medicine, physiology and biophysics at Boston
University School of Medicine and one of the most vocal
proponents of the compound. People in sun-deprived regions
are especially prone to schizophrenia, multiple sclerosis
and Type 1 diabetes, he says.
