26 June 2009
Vitamin D linked to successful weight loss with dieting
Increased intakes of vitamin D may improve weight loss while following a calorie-restricted diet, according to new findings from the US.
For every increase of 1 ng/mL in level of 25-hydroxycholecalciferol – a measure of vitamin D status - subjects ended up losing almost 0.2 kg more on their calorie-restricted diet, suggest findings presented at the Endocrine Society's 91st Annual Meeting in Washington, DC.
Furthermore, for each 1-ng/mL increase in the active form of vitamin D (1,25-dihydroxycholecalciferol), subjects lost 0.107 kg more.
“Our results suggest the possibility that the addition of vitamin D to a reduced-calorie diet will lead to better weight loss,” said the study's lead author, Shalamar Sibley, MD, from the University of Minnesota.
With obesity rates still high – not only in developed countries but also, increasingly, in newly wealthy emerging markets, there is considerable attention to ways to trim down waistlines.
The details on D
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.
While our bodies do manufacture vitamin D on exposure to sunshine, the levels in some northern countries are so weak during the winter months that our body makes no vitamin D at all, meaning that dietary supplements and fortified foods are seen by many as the best way to boost intakes of vitamin D.
In adults, it is said vitamin D deficiency may precipitate or exacerbate osteopenia, osteoporosis, muscle weakness, fractures, common cancers, autoimmune diseases, infectious diseases and cardiovascular diseases. There is also some evidence that the vitamin may reduce the incidence of several types of cancer and type-1 diabetes.
Sibley and her co-workers said that previous studies had reported an association between vitamin D deficiency and obesity, but “it is not clear if inadequate vitamin D causes obesity or the other way around”, she said.
The Minnesota-based researchers recruited 38 overweight men and women and followed assigned them to a calorie-restricted diet, which provided 750 calories a day fewer than their estimated total needs, for 11 weeks. Blood levels of vitamin D were measured before and after the 11 week period.
Sibley told attendees in Washington DC that, on average, many of the subjects were vitamin D insufficient. Moreover, pre-diet levels of the vitamin were linked to weight loss in a linear relationship, she said.
Additionally, higher baseline vitamin D levels of both 25(OH)D and 1,25(OH)2D were linked to increased loss of abdominal fat.
Sibley added a note of caution, saying that more research is needed. “Our findings need to be followed up by the right kind of controlled clinical trial to determine if there is a role for vitamin D supplementation in helping people lose weight when they attempt to cut back on what they eat.”
The study was funded by the National Institutes of Health, the University of Minnesota, and the Pennock Family Endowment at the University of Minnesota.