Calcium, vitamin D may help lower breast cancer risk before menopause

Women who consume more calcium and vitamin D may be less likely to develop breast cancer before menopause, a new U.S. study suggests.

The study tracked more than 10,000 premenopausal and more than 20,000 postmenopausal women aged 45 or older for an average of 10 years.

Participants filled in questionnaires about their diet, lifestyle and medical history. Theywere all free of cancer and heart disease when the study began.

During the followup, 276 premenopausal women and 743 postmenopausal women developed breast cancer.

Higher intakes of total calcium and vitamin D were moderately linked with a lower risk of breast cancer in premenopausal women, but not after menopause, Jennifer Hsiang-Ling Lin at Brigham and Women's Hospital and Harvard Medical School, Boston, and her colleagues report in Monday's issue of the Archives of Internal Medicine.

"The lower risk was more pronounced in more aggressive breast tumours," the study's authors wrote. Faster growing tumours tend to be diagnosed more often in younger women.

Premenopausal women with the highest calcium intake, of more than 1,300 milligrams a day, had a 40 per cent lower risk of the disease compared to those with the lowest consumption of the mineral.

Among those with the highest vitamin D intake, about 550 international units a day, the risk was about 35 per cent lower compared to women who ate the lowest amount of the vitamin.

Vitamin D from food and supplements was included in the study, but sun exposure, which the researchers said is the major source for most people, was not.

Test tube studies suggest that calcium and vitamin D may work with insulin-like growth factors to discourage the growth of breast-cancer cells, the researchers said.

Observation was 'unexpected'

They did not offer any new explanations for why the nutrients may help protect against breast cancer, calling the observation "unexpected."

"Further investigation is warranted to study the potential utility of calcium and vitamin D intake in reducing the risk of breast cancer," the study's authors concluded.

Most experts believe the current recommendation of 400 units of vitamin D a day for people up to age 50, and 600 units daily for those over 70, is probably too low, according to the Canadian Cancer Society, which suggests somewhere between 400 units and the upper safe limit of 2,000 units a day.

Calcium can be found naturally in broccoli anddairy foods such as milk andcheese, and is often added to fortify foods such as orange juice and cereals.

Vitamin D is found in fatty fish and egg yolks, andsoy beverages, orange juice and cheese may be fortified with it.