Vitamin D Lowers Cancer Risk

Vitamin D Lowers Cancer Risk in Older Women in Most Rigorous Study So Far
Thursday, June 7, 2007 1321 PDT


OMAHA, Nebraska -- Building hope for one pill to prevent many cancers,
vitamin D cut the risk of several types of cancer by 60% overall for older
women in the most rigorous study yet.

The new research strengthens the case made by some specialists that vitamin
D may be a powerful cancer preventive and most people should get more of it.
Experts remain split, though, on how much to take.

"The findings ... are a breakthrough of great medical and public health
importance," declared Cedric Garland, a prominent vitamin D researcher at
the University of California-San Diego. "No other method to prevent cancer
has been identified that has such a powerful impact."

While the most reliable yet, the study does have drawbacks. It was designed
mainly to monitor how calcium and vitamin D improve bone health, and the
number of cancer cases overall was small, showing up in just 50 patients.

"It's a very small study," said Dr. Edward Giovannucci, who researches
nutrition and cancer at the Harvard School of Public Health. "I don't think
it's the last word."

In either case, the study takes an important step in extending several
decades of research that began with observations that cancer rates among
similar groups of people were lower in southern latitudes than in northern
ones. Scientists reasoned that had to do with more direct sunlight in
southern regions.

The skin makes vitamin D when exposed to sunlight's ultraviolet rays. This
study used that same form of the vitamin, known as D3 or cholecalciferol.
Multivitamins usually carry a much weaker variant known as D2, but D3 is
available in stand-alone dietary supplements.

Earlier research has shown that vitamin D helps regulate cell growth, a
fundamental biological process that goes haywire in cancer. Most other
supplements have tended to target specific types of disease in early
testing, like selenium or vitamin E for prostate cancer.

This study, published Friday in the American Journal of Clinical Nutrition,
is the first time that researchers significantly boosted - and measured -
blood levels of vitamin D and then followed identical groups of patients
from start to finish.

That's why, despite its modest size, the research was generating excitement.
Nearly all other work has compared disparate groups of patients.

The researchers at Creighton University in Omaha focused on 1,179 seemingly
healthy women with an average age of 67. The women were divided into 3
groups: 446 got calcium and vitamin D3 supplements, a similar number got
calcium alone, and 288 took dummy pills.

The research team gave 1,000 daily international units of vitamin D, more
than current guidelines calling for 200 to 600 IU depending on a person's
age.

The researchers intended to check mainly for the effects of calcium on bone
health. Their interest in cancer risk was secondary.

But the lower cancer risk stood out. Only 13 women, or 3%, developed cancer
over 4 years of calcium and vitamin D supplements. With calcium alone, 17
women, or 4%, got cancer. With dummy pills, cancer appeared in 20 women, or
7%.

That shows a 60 percent lower cancer risk over 4 years in the group taking
both supplements, compared to patients taking placebos. And when the
1st-year cancers were excluded - the ones mostly likely present before the
study began - the findings were stronger still: a 77% lower risk for the
combo group.

While the calcium-only group lowered its 4-year cancer risk by 47% compared
to the untreated group, it did no better when early cancers were excluded.
That suggests calcium alone may have done little in this experiment, the
researchers said.

Experts reviewing the study focused on vitamin D as the powerful agent in
the combo group, but it can't be ruled out that calcium might somehow
amplify the effect of vitamin D.

While numbers were limited, these women developed a broad range of cancers,
including disease of the breast, colon, lungs and blood. Dr. Michael
Holick, of Boston University Medical Center, who sat on the professional
panel that issued the 1997 guidelines for vitamin D, said this study shows
that enough vitamin D "markedly reduces the risk of developing the most
serious deadly cancers."

He supports raising the recommended amount of the vitamin and said 1,000
daily units of vitamin D3 would now be reasonable for most people.

On the other hand, Dr. Michael Thun of the American Cancer Society favors
keeping the current recommendation of 200 to 600 IUs for now. And he
cautioned that more than 2,000 units is viewed in the guidelines as
potentially dangerous.

Joan Lappe, the study's lead researcher, said it "just adds to the great
bunch of evidence that we need to have better vitamin D nutrition." Some
foods carry the vitamin, like salmon, tuna and fortified milk, but diet
accounts for little of the vitamin circulating in the body. Overexposure to
the sun can cause skin cancer.

Still, people should consult their doctors before boosting their vitamin
dosage, several experts also warned.

More study is needed to determine if the effects in this study hold true for
large groups of people and men as well as women.
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On the Net:

Vitamin D fact sheet:

http://dietary-supplements.info.nih....nd.aspbold_off

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