How important is vitamin D supplementation to osteoporotic fracture prevention?
Response From the Expert
Susan A. New, BA, MSc, PhD, RPHNutr
Center for Nutrition & Food Safety, School of Biomedical & Life Sciences, University of Surrey, Guildford, Surrey, United Kingdom
Bottom line: Vitamin D supplementation is absolutely critical to bone health in the aging population. Although a number of research questions still need to be addressed, there is currently sufficient evidence to show that all women, living in areas of Northern Latitude, should be taking a vitamin D (and calcium) supplement.
Vitamin D (in combination with parathyroid hormone [PTH]) plays a vital role in the regulation of calcium and phosphorus metabolism, promoting Ca absorption from the gut and kidney tubules. Supplementation trials have shown vitamin D to improve calcium absorption, lower PTH levels, and reduce wintertime bone loss in postmenopausal women. Vitamin D and calcium supplementation studies have been shown to significantly reduce fracture rates in both institutionalized and free-living elderly populations. The results of the study by Chapuy and colleagues have recently been confirmed in a follow-up study.
Of intrigue is the finding that vitamin D supplementation alone is not effective. In one of the most recent studies, Meyer and coworkers investigated the use of cod liver oil containing 10 microg (400 IU) of vitamin D, and found that it did not prevent osteoporotic fractures in 1144 nursing home residents. A point of note is the difference between vitamin D supplementation levels. In the studies by Chapuy and Dawson-Hughes, 20 microg/d and 17.5 microg/d of vitamin were supplemented, respectively, whereas in the studies by Lips and Meyer, only 10 microg/d were used, without additional calcium.
The effect of vitamin D and calcium supplementation on the risk of falling and muscle strength has also been examined in the elderly population with some interesting findings. In a recent study by Bishoff and colleagues, the study design was a randomized, double-blind, placebo-controlled investigation involving a total of 122 elderly women who resided in a long-stay geriatric healthcare institution. The age range of subjects was 63-99 years, with a mean of 85.3 years. Subjects received either a 1200-mg calcium supplement together with 800 IU of cholecalciferol (calcium + vitamin D group) or calcium alone (1200 mg). The numbers of falls were recorded for a period of 6 weeks before treatment and a further 12 weeks during the treatment period. Muscle strength was measured as musculoskeletal function, expressed as a summed score of knee flexor and extensor strength, grip strength, and timed up-and-go test. Results showed a 49% reduction of falls (95% CI, 14%-71%; P < .01) in the calcium + vitamin D group, with a parallel improvement in musculoskeletal function (P < .094). Of note, markers of bone turnover were also found to be significantly reduced together with a reduction in PTH excretion. Both serum 25-hydroxyvitamin D and 1,25 di-hydroxyvitamin D were found to be significantly higher in the calcium + vitamin D group.
One further important point: Although it is well documented that vitamin D synthesis from sunlight is affected by the aging process, there is a remarkable lack of awareness about this public health nutrition message. Findings from the United States, United Kingdom, and some European countries have shown that the majority of free-living elderly women and those living in nursing homes have dietary intakes of vitamin D below the recommended levels, and over one third of the institutionalized elderly were vitamin D-deficient. Vitamin D "insufficiency," which has implications for bone health, is high in the elderly population, and they are a clear target group for vitamin D (and calcium) supplementation. There is a great opportunity here for the use of fortified foods.
Medscape Ob/Gyn. 2003;8(2) © 2003
Cite this: Susan A New. Vitamin D Supplementation and Fracture Prevention - Medscape - Sep 11, 2003.