RESEARCH - Trial shows vitamin D fails to prevent bone loss in black women

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Trial shows vitamin D fails to prevent bone loss in black women

Rheumawire

Jul 26, 2005

Gandey

Mineola, NY - A randomized placebo-controlled double-blind trial has found

that vitamin D has no effect on bone loss or bone-turnover markers in

postmenopausal black women [1]. The results of the study, which researchers

say is the first clinical trial examining this effect in blacks, appear in

the July 25, 2005 issue of the Archives of Internal Medicine. Led by Dr

Aloia (Winthrop University Hospital, Mineola, NY), the team reports it had

expected to find the opposite result, anticipating that low levels of

vitamin D in black women caused by reduced dermal synthesis during sun

exposure would be reversed and subsequent improvements observed.

But Dr Cannell, executive director of the Vitamin D Council, says these

results should be interpreted with caution. " I'm concerned this finding will

be used as evidence that you don't need to treat blacks with vitamin D, only

whites, and this is categorically false. Low rates of vitamin D in blacks is

epidemic and leads to unnecessary death. " Cannell says he is concerned this

study could be used in a racist way, encouraging substandard treatment in

blacks.

Cannell notes that while the finding of this trialthat vitamin D levels do

not have an effect on bone loss in blacksmay prove to be valid, there are

many other benefits that have not been taken into account, such as its

effect on type 2 diabetes, colon cancer, heart disease, and hypertension.

Cannell also suggests that the level of vitamin usedpeaking at 2000 IUmay be

only half the dose required by black women. However, he compliments the

researchers on this dosage. " To my knowledge, " he told rheumawire, " this is

the highest dose ever studied and I congratulate the authors. "

In this trial, the investigators assigned more than 200 healthy black

postmenopausal women to receive either placebo or 20 g/day (800 IU) of

vitamin D3. They also supplied calcium supplements to the women, aged 50 to

75 years, to ensure a total calcium intake of 1200 to 1500 mg/day. After two

years, they increased the dose of vitamin D to 50 g/day (2000 IU) in the

active group, and the study continued for another year. They measured

bone-mineral density every six months, and markers of bone turnover, vitamin

D metabolites, and parathyroid hormone levels were measured in serum.

Aloia and colleagues found no significant differences in bone-mineral

density between the active and placebo groups throughout the study. They

observed no relation between serum 25-hydroxyvitamin D levels attained and

rates of bone loss. They found an increase in bone-mineral density of the

total body, hip, and radius at one year in both groups. Over the three

years, bone-mineral density declined at these sites, by between 0.26% and

0.55% per year. The bone-mineral density of the lumbar spine increased

slightly in the placebo and active groups. They found no persistent changes

in serum parathyroid hormone levels or in the markers of bone turnover,

although there was a transient decline in parathyroid hormone in both groups

at three months. The team reports no significant adverse events with vitamin

D supplementation.

" Further studies are needed to determine if these findings are applicable to

women of other ethnic groups, " conclude Aloia and his team. They note that

although there is general agreement on the optimal calcium intake

recommended for reducing postmenopausal bone loss and it is recognized that

vitamin D is important in calcium maintenance, the optimal intake of vitamin

D remains controversial.

Source

1. Aloia JF, Arunabh Talwar S, Pollack S, et al. A randomized

controlled trial of vitamin D3 supplementation in African American women.

Arch Intern Med 2005; 165:1618-1623.

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Mayo Clinic in Rochester

http://www.mayoclinic.org/rochester

s Hopkins Medicine

http://www.hopkinsmedicine.org