Vitamin D Benefits and Metabolism May Depend on Body Weight

Researchers have found new evidence that vitamin D may be metabolized differently in people with an elevated body mass index (BMI). 

Vitamin D is an essential nutrient involved in many biological processes, most notably helping our body absorb minerals, such as calcium and magnesium. While some of the vitamin D we need is made in the body from sunlight, vitamin D deficiencies are often treated with supplementation. 

“The analysis of the original VITAL data found that vitamin D supplementation correlated with positive effects on several health outcomes, but only among people with a BMI under 25,” said first author Deirdre K. Tobias, ScD. “There seems to be something different happening with vitamin D metabolism at higher body weights, and this study may help explain diminished outcomes of supplementation for individuals with an elevated BMI.”

The VITAL trial included men over the age of 50 and women over the age of 55. All participants were free of cancer and cardiovascular disease at the time of enrollment. While the trial found little benefit of vitamin D supplementation for preventing cancer, heart attack, or stroke in the overall cohort, there was a statistical correlation between BMI and cancer incidence, cancer mortality, and autoimmune disease incidence. 

The new study aimed to investigate this correlation. The researchers measured the levels of total and free vitamin D, as well as many other novel biomarkers for vitamin D, such as its metabolites, calcium, and parathyroid hormone, which helps the body utilize vitamin D.

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

“This study sheds light on why we’re seeing 30-40 percent reductions in cancer deaths, autoimmune diseases, and other outcomes with vitamin D supplementation among those with lower BMIs but minimal benefit in those with higher BMIs, suggesting it may be possible to achieve benefits across the population with more personalized dosing of vitamin D,” said Manson. 

The authors conclude that the VITAL findings are a call to action for the research community to continue exploring the potential benefits of vitamin D supplementation for preventing cancer and other diseases and to take BMI into account when evaluating the supplement’s health impacts.


Deirdre K. Tobias, Heike Luttmann-Gibson, Samia Mora, Jacqueline Danik, Vadim Bubes, Trisha Copeland, Meryl S. LeBoff, Nancy R. Cook, I-Min Lee, Julie E. Buring, JoAnn E. Manson. Association of Body Weight With Response to Vitamin D Supplementation and Metabolism. JAMA Network Open, 2023; 6 (1): e2250681 DOI: 10.1001/jamanetworkopen.2022.50681

Brigham and Women’s Hospital. “Vitamin D benefits and metabolism may depend on body weight: People with higher body mass index had a blunted response to vitamin D supplementation, explaining observed differences in outcomes such as cancer, diabetes, and autoimmune disease.” ScienceDaily. ScienceDaily, 17 January 2023. <>.

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