Scientists Say Sunshine May Prevent Cancer

Roman Bystrianyk · medicine forum Guru Joined: 02 May 2005 Posts: 454

http://www.healthsentinel.com/news.php?event=news_print_list_item&id=847

Marilynn Marchione, "Scientists Say Sunshine May Prevent Cancer",
Chicago Tribune, May 23, 2005,
Link:
http://www.chicagotribune.com/news/nationworld/sns-ap-sunshine--cancer,1,4260327.story?coll=chi-news-hed

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."

On the Net:

Government information:

http://ods.od.nih.gov/factsheets/vitamind.asp

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