A daily dose of 1,000 International Units (25 micrograms) was also associated with increases in LDL cholesterol, but the data suggested that the form of LDL became ‘less atherogenic’, compared with the placebo group, Iranian researchers report in the peer-reviewed British Journal of Nutrition.
Supplements of the sunshine vitamin were also associated with a significant reduction in body fat mass, compared with placebo, added researchers from the Tehran University of Medical Sciences.
“Although vitamin D3 supplementation significantly increased 25(OH)D concentrations, some participants in the vitamin D group did not reach sufficient 25(OH)D concentrations,” they wrote.
“It seems that they may need higher doses or a longer period of time to be supplemented.”
Vitamin D refers to two biologically inactive precursors - D3, also known as cholecalciferol, and D2, also known as ergocalciferol. Both D3 and D2 precursors are transformed in the liver and kidneys into 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.
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.
Vitamin D deficiency in adults is reported to 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 and -2 diabetes.
The Tehran-based researchers recruited 77 overweight and obese women with an average age of 38 and randomly assigned them to receive either the daily vitamin D3 supplements or placebo for 12 weeks.
Data showed that HDL cholesterol levels increased in the vitamin D group, but decreased in the placebo group. LDL-cholesterol levels displayed the same trend in the groups, said the researchers, with increases observed in the vitamin group.
However, an increase was observed in the ratio of LDL to ApoB, the main apolipoprotein of LDL cholesterol that is responsible for the transport of cholesterol to tissues.
This result “indicates less atherogenic properties of LDL-cholesterol particles, whereas this ratio declined in the placebo group indicating that LDL-cholesterol particles were smaller and had higher density,” explained the researchers.
“The present study is one of the first reports about the effect of vitamin D3 supplementation solely on blood lipids and lipoproteins in healthy overweight and obese women,” they added.
“The present study has shown that although the daily intake of a 25 micrograms vitamin D3 supplement increases total and LDL-cholesterol concentrations, it has a beneficial effect on HDL-cholesterol, apoA-I concentrations, apoA-I:apo B-100 and LDL-cholesterol:apoB-100 ratios in overweight and obese women.”
Source: British Journal of Nutrition
Published online ahead of print, FirstView Article, doi: 10.1017/S0007114512000098
“Vitamin D3 and the risk of CVD in overweight and obese women: a randomised controlled trial”
Authors: A. Salehpour, F. Shidfar, F. Hosseinpanah