Daily supplements of vitamin D may reduce levels of C-reactive protein (CRP), a marker of chronic inflammation, in obese and overweight women, but only if the women take the supplements every day, says a new study.
Data from 218 overweight and obese women indicated that vitamin D3 supplements did not influence weight loss or other factors for the overall study population. However, for women who adhered to the daily supplement regime, a greater decrease in CRP levels was measured, compared to placebo.
Chronic inflammation is brought about by an over-expression or lack of control of the normal protective mechanisms. The link between inflammation and chronic disease has been strengthened by identification and acceptance of these biomarkers. Indeed, an article in the New England Journal of Medicine (2004, Vol. 351, pp. 2599-2610) evaluated the role of inflammatory markers heart disease risk in women, and concluded: “Elevated levels of inflammatory markers, particularly C-reactive protein, indicate an increased risk of coronary heart disease”.
However, no significant changes were observed for waist circumference, weight, percentage body fat between the vitamin D3 group and the placebo, report researchers from the Fred Hutchinson Cancer Research Center in Seattle in the American Journal of Clinical Nutrition .
“Vitamin D has multiple physiologic functions beyond its classically recognized role in calcium homeostasis and bone metabolism,” they explained. “Vitamin D receptors are found in over 30 cell types, including adipocytes, and a growing body of evidence has implicated vitamin D status in a range of adverse health conditions in addition to premature mortality from all causes, cardiovascular disease, and cancer.
“Despite previous observations of reduced serum vitamin D with increased adiposity, vitamin D supplementation of 2000 IU/d in women with insufficient concentrations at baseline had no overall effect on weight or fat loss in postmenopausal women consuming a calorie-restricted diet and following an exercise program.”
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).
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.
Led by Caitlin Mason, the researchers recruited 218 overweight and obese women aged between 50 and 75 to participate in their randomized, placebo-controlled trial. Women on a weight loss and were randomly assigned to receive either vitamin D3 supplements (2,000 IU per day) or placebo for 12 months.
Results showed that, of the 188 women who completed the study, there were no significant differences between the vitamin D3 group and placebo for weight or fat loss, nor were there any overall differences in CRP levels between the groups.
However, among the women with a good compliance to the supplement program, defined as 97% adherence, a significantly larger decrease in CRP of 46% was observed, compared with a 25% decrease for the placebo group.
“Thus, low pill compliance in a subset of study participants may have diminished the strength of the observed outcomes and suggests that future study designs to test vitamin D effects should use methods to optimize study medication adherence, such as once-weekly dosing, medication diaries, reminder phone or electronic messaging, electronic pill bottle counting, and more frequent clinic visits for monitoring and promoting compliance,” they said.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:10.3945/ajcn.113.073734
“Vitamin D3 supplementation during weight loss: a double-blind randomized controlled trial”
Authors: C. Mason, L. Xiao, I. Imayama, C. Duggan, C-Y. Wang, L. Korde, A. McTiernan