High BMI may blunt response to vitamin D

A recent study suggested that an elevated body mass index (BMI) may diminish the positive effects of vitamin D supplementation.

The study was published in the journal, JAMA Network Open, and conducted by researchers from Brigham and Women’s Hospital in Boston. According to the study’s authors, vitamin D is an essential nutrient involved in many biological processes. Research suggests that vitamin D may help decrease the incidence of cancer and cardiovascular disease. Previous studies have also indicated an association between BMI and the benefits of vitamin D in outcomes such as cancer. For the investigation, scientists sought to understand the relationship between BMI and the effects of vitamin D supplementation on disease risk.

To do this, researchers analyzed data from the VITAL trial, a nationwide clinal trial by Brigham Hospital investigating the impact of vitamin D and marine omega-3 on the risk of developing cancer, heart disease, and stroke. The VITAL trial included 25,871 cancer and cardiovascular disease-free U.S. participants who were either men over the age of 50 or women over the age of 55. Results showed little evidence of the benefits of vitamin D supplementation. However, there was a statistical correlation between BMI and cancer incidence, cancer mortality, and autoimmune disease incidence.

For the new study, researcher used data from 16,515 participants who provided blood samples before starting vitamin D supplements as well as 2,742 participants who had follow-up blood samples taken after two years. Scientists measured the participants’ levels of total and free vitamin D as well as biomarkers for vitamin D like metabolites, calcium, and parathyroid hormone.

Results showed that vitamin D supplementation increased most of the biomarkers associated with vitamin D metabolism in participants regardless of their weight. However, researchers found that these increases were significantly smaller in people with elevated BMIs.

"We observed striking differences after two years, indicating a blunted response to vitamin D supplementation with higher BMI," said first author, Deirdre Tobias, ScD, an associate epidemiologist in Brigham’s Division of Preventative Medicine. "This may have implications clinically and potentially explain some of the observed differences in the effectiveness of vitamin D supplementation by obesity status."

According to the study’s authors, these findings suggest that vitamin D supplementation may be more effective with personalized doses depending on a patients BMI. Future investigations, researchers said, should continue to explore the potential benefits of vitamin D on the risk of cancer and cardiovascular disease while taking BMI into account.