Most of us know that vitamin D works with calcium to grow strong bones and to prevent osteoporosis. However, researchers have found that vitamin D has additional important effects on the body. Studies have shown that adequate circulating levels of vitamin D may decrease risk for developing heart disease, cerebrovascular disease, diabetes, cancer and/or falls.
Adequate vitamin D and its receptors (VDR’s) in skeletal muscle promote growth of muscle proteins, enhancing strength and function. A drop in vitamin D levels causes protein breakdown and loss of muscle fibers, known as sarcopenia. Vitamin D deficiency also reduces energy production for muscle contraction. Taken together, these effects cause muscles to weaken, affect walking ability and balance, and increase risk for falls. Conversely, researchers have found that individuals with high circulating levels of vitamin D experience fewer falls than those with low levels of this nutrient.
Vitamin D appears to have a protective effect against certain types of cancers, especially colon and colorectal cancers, by regulating cell cycles and causing cancer cell death. There is mixed evidence that vitamin D reduces breast cancer risk. More research is needed to clarify this effect.
Cardiovascular and cerebrovascular diseases have been linked to chronic inflammation and production of cellular proteins called cytokines. Adequate vitamin D levels suppress cytokine production and decrease inflammation. Additionally, high vitamin D levels and VDR’s in the heart and blood vessels are associated with low risk of heart attack. There is strong evidence that good vitamin D status reduces the risk for stroke.
Vitamin D is acquired through two main sources: 1) consumption of vitamin D-rich foods and supplements and 2) production of vitamin D in the skin when it is exposed to ultraviolet light from the sun. Foods highest in vitamin D are fish such as cod, salmon, tuna and mackerel. Meats are next, followed by foods fortified with vitamin D, such as orange juice, yogurt, margarine, cereal.
Surprisingly, most adults and older adults in industrialized nations are deficient in vitamin D, and this trend continues to grow. Reasons include decreased exposure to sunlight, attributed to time spent indoors and increased use of sunscreen, and reduced consumption of vitamin D-rich foods. Vitamin D status declines with age due to reduced dietary consumption and intestinal absorption, decreases in skin conversion and losses in kidney function. So the time to work on your vitamin D status is now!
There is disagreement among government health agencies regarding the recommended daily allowance for vitamin D. The Institute of Medicine recommends daily consumption of 400 IU for individuals aged 51-70 years and 600 IU for those older than 70 years. However, recent studies demonstrated that higher doses appeared more effective (e.g., 1000-2000 IU).
Be sure to talk with your physician prior to purchasing any supplements. He or she can do a blood test to determine your vitamin D levels, and then prescribe the amount of this nutrient that is appropriate for you.
Constance McCloy, PT, EdD
Kikkinen A et al. Vitamin D status and the risk of cardiovascular disease death. American Journal of Epidemiology. 2009;170:1032-1039.
National Institutes of Health Dietary Supplement Factsheet: Vitamin D. http://ods.od.nih.gov/factsheets/vitamind.asp Retrieved July 19, 2010.
Ruxton CH and Derbyshire E. Health impacts of vitamin D: are we getting enough? British Nutrition Foundation Nutrition Bulletin. 2009;34:185-197.
Schact E and Richy F. Reduction of falls in elderly: the central role of alfacalcidol in a multi-dimensional paradigm. Internet Journal of Epidemiology. 2009;7:1-14.
Zhou G, Stoitzfus J, Swan B. Optimizing vitamin D status to reduce colorectal cancer risk: an evidentiary review. Clinical Journal of Oncology Nursing. 2009;13:E3-E17.