Vitamin D research may have doctors prescribing sunshine
The Associated
Press
Scientists are
excited about a vitamin again. But unlike fads that sizzled and
fizzled, the evidence this time is strong and keeps growing.
If it bears out, it will
challenge one of medicine's most fundamental beliefs: that
people need to coat themselves with sunscreen whenever they're
in the sun. Doing that may actually contribute to far more
cancer deaths than it prevents, some researchers think.
The vitamin is D, nicknamed
the "sunshine vitamin" because the skin makes it from
ultraviolet rays. Sunscreen blocks its production, but
dermatologists and health agencies have long preached that such
lotions are needed to prevent skin cancer.
Now some scientists are
questioning that advice.
The reason is that vitamin D
increasingly seems important for preventing and even treating
many types of cancer. In the last three months alone, four
separate studies found it helped protect against lymphoma and
cancers of the prostate, lung and, ironically, the skin. The
strongest evidence is for colon cancer.
Many people aren't getting
enough vitamin D. It's hard to do from food and fortified milk
alone, and supplements are problematic.
So the thinking is this:
Even if too much sun leads to skin cancer, which is rarely
deadly, too little sun may be worse.
No one is suggesting that
people fry on a beach. But many scientists believe that "safe
sun" — 15 minutes or so a few times a week without sunscreen —
is not only possible but helpful to health.
One is Dr. Edward
Giovannucci, a Harvard University professor of medicine and
nutrition who laid out his case in a keynote lecture at a recent
American Association for Cancer Research meeting in Anaheim,
Calif.
His research suggests that
vitamin D might help prevent 30 deaths for each one caused by
skin cancer.
"I would challenge anyone to
find an area or nutrient or any factor that has such consistent
anti-cancer benefits as vitamin D," Giovannucci told the cancer
scientists. "The data are really quite remarkable."
The talk so impressed the
American Cancer Society's chief epidemiologist, Dr. Michael
Thun, that the society is reviewing its sun protection
guidelines. "There is now intriguing evidence that vitamin D may
have a role in the prevention as well as treatment of certain
cancers," Thun said.
Even some dermatologists may
be coming around. "I find the evidence to be mounting and
increasingly compelling," said Dr. Allan Halpern, dermatology
chief at Memorial Sloan-Kettering Cancer Center in New York, who
advises several cancer groups.
The dilemma, he said, is a
lack of consensus on how much vitamin D is needed or the best
way to get it.
No source is ideal. Even if
sunshine were to be recommended, the amount needed would depend
on the season, time of day, where a person lives, skin color and
other factors. Thun and others worry that folks might overdo it.
"People tend to go overboard
with even a hint of encouragement to get more sun exposure,"
Thun said, adding that he'd prefer people get more of the
nutrient from food or pills.
But this is difficult.
Vitamin D occurs naturally in salmon, tuna and other oily fish,
and is routinely added to milk. However, diet accounts for very
little of the vitamin D circulating in blood, Giovannucci said.
Supplements contain the
nutrient, but most use an old form — D-2 — that is far less
potent than the more desirable D-3. Multivitamins typically
contain only small amounts of D-2 and include vitamin A, which
offsets many of D's benefits.
As a result, pills might not
raise vitamin D levels much at all.
Government advisers can't
even agree on an RDA, or recommended daily allowance for vitamin
D. Instead, they say "adequate intake" is 200 international
units a day up to age 50, 400 IUs for ages 50 to 70, and 600 IUs
for people over 70.
Many scientists think adults
need 1,000 IUs a day. Giovannucci's research suggests 1,500 IUs
might be needed to significantly curb cancer.
How vitamin D may do this is
still under study, but there are lots of reasons to think it
can:
_Several studies observing
large groups of people found that those with higher vitamin D
levels also had lower rates of cancer. For some of these
studies, doctors had blood samples to measure vitamin D, making
the findings particularly strong. Even so, these studies aren't
the gold standard of medical research — a comparison over many
years of a large group of people who were given the vitamin with
a large group who didn't take it. In the past, the best research
has deflated health claims involving other nutrients, including
vitamin E and beta carotene.
_Lab and animal studies show
that vitamin D stifles abnormal cell growth, helps cells die
when they are supposed to, and curbs formation of blood vessels
that feed tumors.
_Cancer is more common in
the elderly, and the skin makes less vitamin D as people age.
_Blacks have higher rates of
cancer than whites and more pigment in their skin, which
prevents them from making much vitamin D.
_Vitamin D gets trapped in
fat, so obese people have lower blood levels of D. They also
have higher rates of cancer.
_Diabetics, too, are prone
to cancer, and their damaged kidneys have trouble converting
vitamin D into a form the body can use.
_People in the northeastern
United States and northerly regions of the globe like
Scandinavia have higher cancer rates than those who get more
sunshine year-round.
During short winter days,
the sun's rays come in at too oblique an angle to spur the skin
to make vitamin D. That is
why nutrition experts think vitamin D-3 supplements may be
especially helpful during winter, and for dark-skinned people
all the time.
But too much of the pill
variety can cause a dangerous buildup of calcium in the body.
The government says 2,000 IUs is the upper daily limit for
anyone over a year old.
On the other hand, D from
sunshine has no such limit. It's almost impossible to overdose
when getting it this way. However, it is possible to get skin
cancer. And this is where the dermatology establishment and Dr.
Michael Holick part company.
Thirty years ago, Holick
helped make the landmark discovery of how vitamin D works. Until
last year, he was chief of endocrinology, nutrition and diabetes
and a professor of dermatology at Boston University. Then he
published a book, "The UV Advantage," urging people to get
enough sunlight to make vitamin D.
"I am advocating common
sense," not prolonged sunbathing or tanning salons, Holick said.
Skin cancer is rarely fatal,
he notes. The most deadly form, melanoma, accounts for only
7,770 of the 570,280 cancer deaths expected to occur in the
United States this year.
More than 1 million milder
forms of skin cancer will occur, and these are the ones tied to
chronic or prolonged suntanning.
Repeated sunburns —
especially in childhood and among redheads and very fair-skinned
people — have been linked to melanoma, but there is no credible
scientific evidence that moderate sun exposure causes it, Holick
contends.
"The problem has been that
the American Academy of Dermatology has been unchallenged for 20
years," he says. "They have brainwashed the public at every
level."
The head of Holick's
department, Dr. Barbara Gilchrest, called his book an
embarrassment and stripped him of his dermatology professorship,
although he kept his other posts.
She also faulted his
industry ties. Holick said the school has received $150,000 in
grants from the Indoor Tanning Association for his research, far
less than the consulting deals and grants that other scientists
routinely take from drug companies.
In fact, industry has spent
money attacking him. One such statement from the Sun Safety
Alliance, funded in part by Coppertone and drug store chains,
declared that "sunning to prevent vitamin D deficiency is like
smoking to combat anxiety."
Earlier this month, the
dermatology academy launched a "Don't Seek the Sun" campaign
calling any advice to get sun "irresponsible." It quoted Dr.
Vincent DeLeo, a Columbia University dermatologist, as saying:
"Under no circumstances should anyone be misled into thinking
that natural sunlight or tanning beds are better sources of
vitamin D than foods or nutritional supplements."
That opinion is hardly
unanimous, though, even among dermatologists.
"The statement that 'no sun
exposure is good' I don't think is correct anymore," said Dr.
Henry Lim, chairman of dermatology at Henry Ford Health System
in Detroit and an academy vice president.
Some wonder if vitamin D may
turn out to be like another vitamin, folate. High intake of it
was once thought to be important mostly for pregnant women, to
prevent birth defects. However, since food makers began adding
extra folate to flour in 1998, heart disease, stroke, blood
pressure, colon cancer and osteoporosis have all fallen,
suggesting the general public may have been folate-deficient
after all.
With vitamin D, "some people
believe that it is a partial deficiency that increases the
cancer risk," said Hector DeLuca, a University of
Wisconsin-Madison biochemist who did landmark studies on the
nutrient.
About a dozen major studies
are under way to test vitamin D's ability to ward off cancer,
said Dr. Peter Greenwald, chief of cancer prevention for the
National Cancer Institute. Several others are testing its
potential to treat the disease. Two recent studies reported
encouraging signs in prostate and lung cancer.
As for sunshine, experts
recommend moderation until more evidence is in hand.
"The skin can handle it,
just like the liver can handle alcohol," said Dr. James Leyden,
professor emeritus of
dermatology at the University of Pennsylvania, who has consulted
for sunscreen makers.
"I like to have wine with
dinner, but I don't think I should drink four bottles a day."
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