BEIJING, June 11 (Xinhuanet) -- New research that
reveals vitamin D cut the risk of several types of cancer by 60 percent overall
for older women strengthens the case made by some specialists that most people
should get more of it, but experts are not sure 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."
The study is the most reliable to date, but does have
limitations. It was designed primarily 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."
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 awry 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
¡ª and measured ¡ª blood levels of vitamin D and then followed identical groups of
patients from start to finish.
(Agencies)
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