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Vitamin D Reduces Breast Cancer Risk in Case-Control Study: Presented at AACR

By Rabiya S. Tuma, PhD

WASHINGTON, D.C. -- April 10, 2006 -- In an on-going case-control study, researchers found that increased vitamin D, either through sun exposure or dietary intake, reduced a woman's risk of breast cancer.

Julia Knight, PhD, scientist in the division of epidemiology and biostatistics, Mt. Sinai Hospital, Toronto, Ontario, Canada, presented the study here on April 4^th at the 97^th Annual Meeting of the American Association for Cancer Research (AACR).

Thus far, the team has reviewed data from 576 breast cancer cases identified through the Ontario Cancer Registry and 813 controls identified through randomly selected residential telephone calls. The cases were diagnosed between July 1, 2003 and June 30, 2004 and were aged 20 to 58 years.

Women who worked an outdoor job, which would increase sun exposure, had a 40% reduction in the risk of breast cancer relative to those who had not (95% CI, 0.48-0.75).

Similarly, women who participated in outdoor activities had a reduced risk of breast cancer. Women who participated in more than 6 outdoor activities per week between the ages of 10 and 19 had a 45% risk reduction, relative to those who had fewer than four activities. Women who more than 5 activities between the ages of 20 and 29 had a 28% reduced risk relative to those with fewer than 3 outdoor activities. Outdoor activities included both physically active and inactive ones, suggesting that it was a link to sun exposure rather than exercise.

In terms of dietary intake, the researchers asked participants about cod liver oil and milk. Women who took cod liver oil for 10 years or more had a 34% reduced risk, relative to those who did not (95% CI, 0.40-1.00). Women who consumed at least 9 glasses of milk per week between the ages of 20 and 29 reduced their risk by 25% compared to those who had fewer than 5 glasses per week (95% CI, 0.58-0.99).

"It seems that exposure to vitamin D at the time breasts are developing, particularly around adolescence, might be important," said Dr. Knight.

Sunlight is the major source of vitamin D, said Dr. Knight, though some foods, such as fish, are naturally rich in vitamin D. Additionally, some food fortification, particularly milk, have helped increase vitamin D uptake.


[Presentation title: Potential Reduction in Breast Cancer Risk Associated With Vitamin D. Abstract 4009]

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