I'll never forget my mother's health advice to us as children: Drink your milk, eat your greens and get plenty of fresh air and sunshine.
When it comes to cancer prevention, it turns out mom was right.
Two new studies have uncovered exciting evidence of exceptionally strong cancer-protective effects of calcium and vitamin D from food or supplement sources.
The first study was published last week in the journal Archives of Internal Medicine by Dr. Jennifer Lin and colleagues from Harvard. They report that premenopausal women with high levels of vitamin D and calcium in their diets have a lower risk of breast cancer compared to women with lower intakes of these nutrients.
The second study, published in today's issue of the American Journal of Clinical Nutrition by Dr. Joan M Lappe and colleagues at Creighton University, goes even further: Dietary supplementation of these nutrients reduces the risk of multiple types of cancer.
Together, these studies provide robust evidence of the beneficial effects that calcium and vitamin D can have on cancer prevention.
Research over the past half-century has pointed to a relationship between calcium, vitamin D and reduction of cancer risk, although the results have not been definitive.
In the 1950s, for example, scientists examined weather data and health statistics to show that areas of the country with the highest amount of sunshine, which stimulates the body to make vitamin D, had the lowest rates of colon cancer death.
Since that time, studies in both humans and animals have pointed toward cancer-preventive effects of both vitamin D and calcium, mainly for breast and colon cancers, but for other cancers as well, ranging from prostate cancer to non-Hodgkin's lymphoma.
Lin and her Harvard colleagues focused on these nutrients' effects on breast cancer by analyzing data from the Women's Health Study, funded by the National Institutes of Health.
This study followed 10,578 premenopausal and 20,909 post-menopausal women 45 years or older who were initially free of cancer over 10 years, collecting data on diet, over-the-counter supplement use and subsequent development of breast cancer.
Amazingly, what they found was that calcium and vitamin D intake reduced the risk of developing breast cancer, but only among premenopausal women.
For these women, those with the highest intake of calcium were 39 percent less likely to develop breast cancer than those with the lowest intake. Those in the group with the highest intake of vitamin D were also 35 percent less likely to develop breast cancer.
What's more, high intakes of calcium and vitamin D among premenopausal women seemed to reduce the most aggressive breast tumors, including larger tumors, those which spread to the lymph nodes and those with the most dangerous types of cancer cells.
Unfortunately, among post-menopausal women, there was no relationship between calcium and vitamin D intake and prevention of breast cancer. Nonetheless, when the two nutrients were taken together in high amounts, there was a suggestion of benefit.
In a second study, Lappe and colleagues followed nearly 1,200 women from a nine-county area in eastern Nebraska to see whether vitamin D and calcium supplements might reduce not just breast cancer, but all cancers.