Vitamin D3 supplements may decrease triglyceride levels in at-risk women: RCT data

Elevated triglyceride levels are associated with an increase in the risk of heart disease, according to the Mayo Clinic​, so finding ways to reduce them could have clinical significance.

However, the vitamin D supplementation regime used in the new study did not significantly affect total cholesterol or LDL or HDL levels, report researchers from Mexico’s National Institute of Public Health.

“Our findings do not lack biological importance,”​ wrote the researchers in Clinical Nutrition​,​ “since the decrease we found in serum concentrations of triglycerides and total cholesterol prevents arterial thickening and narrowing, and implies a lowered risk of myocardial infarction and stroke.”​

Vitamin D​

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.

Despite a body of science linking vitamin D to improve heart health, the Mexico-based scientists note that it is unclear if the links are causal, “and if optimum levels of vitamin D is a cause or a consequence of good cardiovascular health”​.

Study details​

Ninety-nine women completed the randomized clinical trial, and were randomly assigned to receive either vitamin D (4,000 IU per day) or placebo for six months.

As expected, vitamin D levels increased in the vitamin group, and these increases were associated with decreases in triglyceride levels. Despite this, no significant changes were observed for cholesterol levels. However, the researchers did note that a non-significant association between vitamin D supplementation and high-density lipoprotein levels were observed.

“Multiple mechanisms could explain the relationship between 25 (OH)D and lipid and lipoproteins concentrations,” ​said the researchers. “Vitamin D might increase calcium absorption, reducing fatty acids in the gut, increasing fat absorption and lowering triglyceride levels. Additionally, in subjects with low concentrations of 25 (OH) D, supplementation with vitamin D might increase uptake of 1,25 (OH)2 D, which has been associated with an increase in lipogenesis and lipolysis.​

“More randomized studies with larger sample sizes and longer terms of follow are needed to further understand the role that vitamin D supplementation plays in the prevention of dyslipidemia and other cardiovascular risk factors,” ​they concluded.

Source: Clinical Nutrition​​
Published online ahead of print, doi: 10.1016/j.clnu.2014.10.002
“The effect of vitamin D supplementation on serum lipids in postmenopausal women with diabetes: A randomized controlled trial”​
Authors: P. Munoz-Aguirre, M. Flores, N. Macias, et al.