Shaklee Health Sciences
Do you know which nutrient is created in your skin when exposed to adequate sunlight, facilitates calcium absorption and is so important to humans that it is considered to be both a vitamin and a hormone? Many of you may have guessed vitamin D and you would be correct! Vitamin D has long been recognized for its essential role in bone health. Working in concert with a number of other vitamins, minerals and hormones, vitamin D helps promote bone mineralization (1). Your body is finely tuned to utilize Vitamin D in the incorporation of calcium and other minerals into supporting the very dynamic process of bone shaping and reshaping and without adequate intakes of vitamin D your bones can become brittle leading to an increased risk of bone fractures and osteoporosis. But there are a number of other functions Vitamin D plays in the body and research is finally beginning to uncover some exciting new health benefits of Vitamin D.
Now there is really exciting new research indicating that vitamin D’s health benefits may shine well beyond bone health. Because vitamin D also plays an important role in maintaining a healthy immune system and regulating cell growth and differentiation (2, 3), the process that determines what a cell is destined to become, supplemental vitamin D may actually be helpful for cancer prevention, in particular prostate, breast and colon cancers (4, 5, 6, 7).
In 2005, Harvard researchers reported the results of a study involving 1029 men with prostate cancer and 1,300 healthy men. After analyzing the blood of these men, researchers found that men with the highest level of vitamin D had significantly lower overall risk (45%) of prostate cancer, including aggressive prostate cancer. In addition, men with a specific receptor that helps vitamin D work got greater protection if they also had high levels of vitamin D in their blood. Those men had a 55% lower risk of prostate cancer and 77% lower risk of aggressive cancer.
Just this year, researchers pooled data from two earlier studies, the Nurses Health Study and the St. George’s Hospital Study and found that women with the highest blood levels of the active form of vitamin D had the lowest risk of breast cancer. Researchers also reported that the level of vitamin D in the blood associated with a 50% reduction in risk could be maintained by taking 2000 IU of vitamin D3 daily plus spending as little as 10-15 minutes a day in the sun (8).
Vitamin D emerged as a protective factor against colon cancer in a study of over 3,000 adults (96% of whom were men) who underwent a colonoscopy between 1994 and 1997 to look for polyps or lesions in the colon. About 10% of the group was found to have at least one advanced cancerous lesion in the colon. However, there was a significantly lower risk of advanced cancerous lesions among men with the highest vitamin D intake.
Such study results have sparked further interest in the role of vitamin D for cancer prevention and more good news for vitamin D has just arrived. In the June 2007, issue of the American Journal of Clinical Nutrition, researchers at the Osteoporosis Research Center at Creighton University discovered that postmenopausal women taking calcium or calcium plus vitamin D for reducing the risk of bone fractures (the primary outcome of the study), got the added benefit of a significant reduction in the risk of cancer. In this study, 1179 healthy, post-menopausal women were randomly assigned to receive 1400-1500 mg of calcium, 1400-1500 mg of calcium plus 1100 IU of vitamin D3, or a placebo. After 4 years, women receiving calcium only reduced their risk of developing cancer by 47% and the women taking calcium plus vitamin D, had a 60% risk reduction!
The findings of such studies really do highlight the importance of achieving optimum vitamin D status. Eating a healthy diet including foods fortified with vitamin D, like reduced fat milk or soy milk is certainly a good place to start. However keep in mind that many dairy products made from milk (e.g. cheese, reduced fat ice cream) are not typically fortified with vitamin D and contain only small amounts. Some ready to eat cereals may be fortified but only a few commonly eaten foods are good sources of vitamin D, like cooked salmon, mackerel and tuna.
Sun exposure for about 10 to 15 minutes at least two times a week can help, but remember sunscreen use which helps reduce the risk of skin cancer, actually blocks vitamin D synthesis in the skin. And if you plan on being out in the sun, make sure you avoid the most dangerous time of the day, between the hours of 10 am to 2 pm.
And of course, one of the safest and most convenient ways to get adequate amounts of vitamin D is to take a multivitamin/mineral supplement and/or a calcium supplement with added vitamin D. Look for a supplement with at least 400 to 800 IU of vitamin D per serving and one that provides the most active form of vitamin D, Vitamin D3 also known as cholecalciferol.
Be well.
Dr. Jamie McManus MD, FAAFP
Chairman, Medical Affairs, Health Sciences and Education
References
- Deluca HF and Zierold C. Mechanisms and functions of vitamin D. Nutr Rev 1998;56:S4-10.
- Hayes CE, Hashold FE, Spach KM, Pederson LB. The immunological functions of vitamin D endocrine system. Cell Mol Biol 200;49:277-300.
- Holick MF. Evolution and function of vitamin D. Recent Results Cancer Res. 2003;164:3-28.
- Martinez ME and Willet WC. Calcium, vitamin D and colorectal cancer: a review of epidemiologic evidence. Cancer Epidemiol. Biomark. Prev 1998;7:163-68.
- Garland C et al. Dietary vitamin D and calcium and risk of colorectal cancer: a 19 year prospective study in men. Lancet 1985;1:307-9.
- H. Li, M. Stampfer, E. Giovannucci et al. Prediagnostic plasma vitamin D levels, vitamin D receptor gene polymorphisms, and susceptibility to prostate cancer. 2005 Prostate Cancer Symposium.
- Leiberman D, et al. Risk factors for advanced colonic neoplasia and hyperplastic polyps in asymptomatic individuals. JAMA 2003;290:2959-67.