Wednesday, May 16, 2007

Supplementation with calcium and vitamin D prevents postmenopausal weight gain?

The authors of this study note that there is a ‘propensity toward postmenopausal gains in fat mass and replacement of lean tissue with adipose tissue’, and data show that the proportion of obese (BMI>30) women between the ages of 50 and 79 years in the US increased by nearly 50% during the 1990s. There are some preliminary data to suggest that calcium and vitamin D may have a role in effective weight management - calcium and 1,25-hydroxyvitamin D regulate lipid metabolism in adipose cells, and calcium may decrease fatty acid absorption through the formation of calcium and fatty acid "soaps" in the intestine.

A total of 36,282 postmenopausal women who were already enrolled in the dietary modification and/or hormone therapy arms of the Women's Health Initiative clinical trial entered into the calcium plus cholecalciferol (vitamin D) randomised trial, which was designed to test whether calcium plus cholecalciferol supplementation would reduce the incidence of hip fracture and colorectal cancer. Personal use of calcium (up to 1000 mg/d) and cholecalciferol (up to 600 IU/d and, after 1999, up to 1000 IU/d) was allowed. Women were randomised at their first or second annual visit to receive 1000 mg of elemental calcium plus 400 IU of cholecalciferol (vitamin D) (n=18,176) or placebo (n=18,106) daily. The primary outcome was weight change, assessed annually for an average of 7 years; all participants with at least 1 weight change measurement were included in the intent-to-treat analysis.

The two groups were similar at baseline in terms of demographic, medical, and lifestyle characteristics, including intake of calcium. The main findings were:

  • Women randomised to supplementation had smaller average annual weight gains than women assigned to placebo, with a mean difference between the groups of –0.13 kg (95% CI –0.21 to –0.05; P=0.001).
  • For women who were the most adherent (consuming >80% of their pills during follow-up); the mean difference in annual weight gain was –0.14 kg in favour of the supplementation (P<0.001).>
  • Women who entered the trial with intakes of calcium lower than the current RDI (<1200>1200 mg)
The authors conclude that ‘even though the overall mean weight change difference between groups was small, women in the active intervention who had inadequate baseline dietary calcium had an 11% lower risk of weight gain during the first 3 years of the trial compared with women with calcium-deficient diets in the placebo group’. They recommend that current dietary recommendations are adhered to, and ‘postmenopausal women should continue to be advised to consume 1200 mg/d of calcium as recommended by of the Food and Nutrition Board of the National Academy of Sciences’.

Arch Intern Med 2007; 167: 893-902 (link to abstract)

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