Vitamin D, Calcium May Prevent, Improve Diabetes

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This article originally posted 10 July, 2007 and appeared in Issue 372

Combined supplementation with vitamin D and calcium may improve blood sugar and insulin levels and prevent diabetes by 64%, suggests a new meta-analysis and review.

Although the evidence to date suggests that vitamin D and calcium deficiency influences post-prandial glycemia and insulin response while supplementation may be beneficial in optimizing these processes, our understanding of the exact mechanisms by which vitamin D and calcium may promote beta cell function, or ameliorate insulin resistance and systemic inflammation is incomplete," wrote lead author Anastassios Pittas.

"It is also not clear whether the effects are additive or synergistic," he added.

Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. The former, produced in the skin on exposure to UVB radiation (290 to 320 nm), is said to be more bioactive. The latter is derived from plants and only enters the body via the diet, from consumption of foods such as oily fish, egg yolk and liver.

Both D3 and D2 precursors are hydroxylated in the liver and kidneys to form 25- hydroxyvitamin D (25(OH)D), the non-active 'storage' form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body

Writing in the Journal of Clinical Endocrinology & Metabolism, Pittas and co-workers reviewed data from observational studies and clinical trials in adults with results related to the control of glucose. The data from observational studies showed a "relatively consistent association" between low intakes of calcium, vitamin D, or dairy intake and type-2 diabetes, with highest levels associated with a 64 per cent lower prevalence of the disease, and a 29 per cent lower prevalence of metabolic syndrome among non-blacks.

When intake of calcium and vitamin D was combined, the inverse associations were still observed, with the highest versus lowest combined intake being associated with an 18 per cent lower incidence of diabetes.

"Evidence from trials with vitamin D and/or calcium supplementation suggests that combined vitamin D and calcium supplementation may have a role in the prevention of type-2 diabetes only in populations at high risk (i.e. glucose intolerance)," wrote the reviewers from Tufts-New England Medical Center.

They noted that research into this area remains limited and called for future research to focus on clarifying and quantifying the link between calcium intake and 25(OH)D levels and the incidence of type-2 diabetes.

Journal of Clinical Endocrinology & Metabolism- June 2007, Volume 92, Number 6, Pages 2017-2029. doi:10.1210/jc.2007-0298 "The Role of Vitamin D and Calcium in type 2 diabetes. A systematic Review and Meta-Analysis" Authors: A.G. Pittas, J. Lau, F. Hu, B. Dawson-Hughes

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FACT:

Women Who Drink a Little May Lower Heart-Attack Risk: Researchers studied 320 women ages 35 to 69 who had had heart attacks, comparing them with 1,565 healthy women matched for age. After adjusting for age, race, education, smoking and body mass index, women who had a daily alcoholic drink had a 31 percent reduced risk of a nonfatal heart attack compared with those who drink less than one drink a day. But among those who drank at all, becoming drunk even once a month — and by that the researchers mean drinking enough to cause slurred speech or unsteady gait — led to an almost sixfold increase in the likelihood of a heart attack. The message is that a small amount is O.K., and drinking to intoxication can be harmful.” the journal Addiction, May 2007