Supplementation with vitamin D₃ has no effect on bone loss or bone turnover markers in calcium-replete, postmenopausal African American women, according to the results of a new placebo-controlled, double-blind study in the July 25 issue of the Archives of Internal Medicine.¹

"African American women have reduced Vitamin D levels due to increased skin pigmentation, which results in less synthesis from the skin," lead researcher John F. Aloia, MD, chief academic officer at Winthrop Hospital in Minneola, New York, tells CIAOMed. "Based on our study, African American patients do not need to take supplements of vitamin D in excess of that which is currently recommended for the general population," he says. As a result, "they should maintain their vitamin D intake in the amount currently recommended by the Food and Nutrition Board." Currently, women aged 51 to 70 are advised to consume 400 IU of vitamin D per day, and women aged 71 or older should consume 600 IU, according to government recommendations.

In the study, 208 healthy, calcium-replete African American women aged 50 to 75 received either placebo or 20 µg/d (800 IU) of vitamin D₃. Calcium supplements were provided to ensure a total calcium intake of 1200 to 1500 mg/d. After 2 years, the vitamin D₃ dose was increased to 50 µg/d (2000 IU) in the active group, and the study continued for an additional year. Bone mineral density (BMD) was measured every 6 months, and bone turnover markers, vitamin D metabolites, and parathyroid hormone (PTH) levels were measured in serum. 

No effect on bone loss or bone turnover markers

Throughout the study, there were no significant differences in BMD between the active and control groups, nor was there any relationship between serum 25-hydroxyvitamin D levels attained and rates of bone loss. There was an increase in BMD of the total body, hip, and radius at 1 year in both groups (between 1.1% and 1.3%). Over the 3 years, BMD declined at these sites by 0.26% to 0.55% per year. The BMD of the lumbar spine increased slightly in the placebo and active groups, and there were no persistent changes in serum PTH levels or bone turnover markers (although there was a transient decline in PTH in both groups at 3 months).

Further studies are needed to determine if these findings are applicable to women of other ethnic groups, Dr. Aloia and his colleagues write. "Race-specific nutrition recommendations for calcium and vitamin D may ... turn out to be appropriate," Dr. Aloia tells CIAOMed.

Vitamin D in the news

Weighing in on some recent studies, which have shown that calcium/vitamin D may not prevent fractures, Dr. Aloia tells CIAOMed that in the past fracture studies were carried out in the elderly, as opposed to middle-aged patients, as in the current study. "These fracture studies in the elderly are contradictory," he says. "It has not been firmly established that 800 units of vitamin D is effective in preventing fractures."

By way of background, CIAOMed recently reported on two recent studies that suggested that regular supplements of calcium and vitamin D may not effectively prevent fractures. In one study of 5292 patients who had sustained a fracture within the last 3 months, patients received either 1 g of calcium, 20 µg of vitamin D3, both, or placebo, but the fracture rate was similar between all groups.²

A second study also found no evidence that calcium and vitamin D supplements reduce the risk of fractures in women aged 70 and over with one or more risk factors for hip fracture.³ By contrast, a meta-analysis showed that a dosage of 700 to 800 IU of vitamin D does reduce the risk of nonvertebral fractures in the elderly.⁴

"However, despite conflicting evidence, my personal opinion is that 1500 mg of calcium with 800 units of vitamin D intake daily should be recommended in the elderly, until the benefit is clarified," Dr. Aloia says.

References

1.       Aloia JF, Talwar SA, Pollack S, Yeh, J. A randomized controlled trial of vitamin D₃ supplementation in African American women. Arch Intern Med. 2005;165:1618-1623.

2. Grant AM, Avenell A, Campbell MK, et al. Oral vitamin D₃ and calcium for secondary prevention of low-trauma fractures in elderly people (Randomized Evaluation of Calcium Or vitamin D, RECORD): a randomized placebo-controlled study. Lancet. 2005;365:1621-1628.

3.       Porthouse J, Cockayne S, King C, et al. Randomized controlled trial of calcium and supplementation with cholecalciferol (vitamin D₃) for prevention of fractures in primary care. BMJ. 2005;330:1003-1006.

4.       Bischoff-Ferrari HA, Willett WC, Wong JB, Giovannucci E, Dietrich T, Dawson-Hughes B. Fracture prevention with vitamin D supplementation: a meta-analysis of randomized controlled trials. JAMA. 2005;293:2257-2264.