Vitamin D Supplementation and Fracture Prevention

Question

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^[1] and free-living elderly^[2] populations. The results of the study by Chapuy and colleagues^[1] have recently been confirmed in a follow-up study.^[3]

Of intrigue is the finding that vitamin D supplementation alone is not effective.^[4] In one of the most recent studies, Meyer and coworkers^[5] 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^[1] and Dawson-Hughes,^[2] 20 microg/d and 17.5 microg/d of vitamin were supplemented, respectively, whereas in the studies by Lips^[4] and Meyer,^[5] 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,^[6] 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,^[7] 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.^[8]

Medscape Ob/Gyn. 2003;8(2) © 2003  Medscape

Cite this: Susan A New. Vitamin D Supplementation and Fracture Prevention - Medscape - Sep 11, 2003.