vitamin d and cancer

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By MARILYNN MARCHIONE, AP Medical Writer Sat May 21,

4:09 PM ET

 

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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