Scientists Say Sunshine May Prevent Cancer

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http://apnews.myway.com/article/20050521/D8A7MPFG0.html

 

Scientists Say Sunshine May Prevent Cancer

May 21, 1:15 PM (ET)

By MARILYNN MARCHIONE

 

(AP) Graphic shows three ways to get vitamin D; two sizes: (AP

Graphic)

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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.

 

 

(AP) Dr. Michael Holick, Ph.D., of Boston University, poses in

a tanning bed at the Boston Medical...

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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. "

 

 

(AP) Dr. Michael Holick, Ph.D., of Boston University, looks

toward the sky while posing for a portrait...

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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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On the Net:

 

Government information:

 

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