Vitamin D is a very important chemical compound for our health. According to research by an American group of scientists, the scale of benefits from supplementing this vitamin may depend on the factor of body mass index.
Researchers at Brigham and Women’s Hospital (Boston, USA) analyzed data from the large national VITAL clinical trial, which looked at whether taking vitamin D or omega-3 supplements could reduce the risk of cancer, heart disease or stroke.
As it turned out, people with a higher body mass index (overweight and obese) responded less to vitamin D supplementation, which may explain the observed differences in outcomes in cancer, diabetes and autoimmune diseases. The results of the analyzes on this subject have been published in the Journal of the American Medical Association (JAMA).
“An analysis of the original VITAL data showed that vitamin D supplementation was correlated with a positive effect on several health markers, but only among those with a BMI below 25,” said lead author Dr. Deirdre K. Tobias of Brigham’s Division of Prevention Medicine. “Something else seems to be going on with vitamin D metabolism at higher body weight, and our study may help explain the less pronounced results of supplementation in those with elevated BMIs,” she added.
An important chemical compound
Vitamin D is an essential nutrient involved in many biological processes, most notably it helps the body absorb calcium and magnesium. Some of the vitamin D a person needs is produced in the body by sunlight, and vitamin D deficiencies are often treated with supplementation. The results of laboratory, epidemiological and clinical studies also suggest that vitamin D may affect the incidence and progression of cancer and cardiovascular diseases. It was this evidence that prompted the original VITAL study.
VITAL was a randomized, double-blind, placebo-controlled study. It was attended by 25,871 people from the USA, including men over 50 and women over 55. At the time of entry into the study, all participants were free from cancer and cardiovascular disease.
Although for the entire study cohort, the study showed little benefit from vitamin D supplementation in preventing cancer, heart attack or stroke, there was a statistical correlation between BMI and cancer incidence, mortality and autoimmune disease. Other studies suggest similar results for type 2 diabetes.
BMI and cancer incidence
A new study set out to explore this correlation. The researchers analyzed data from 16,515 participants in the original study who provided blood samples at the start of the study, as well as from 2,742 with a follow-up blood sample taken two years later. Levels of total and free vitamin D were measured, as well as many other new biomarkers of vitamin D, such as its metabolites, calcium and parathyroid hormone, which helps the body use vitamin D.
“Most of these studies focus on total blood vitamin D levels,” said senior author Dr. Joann E. Manson, head of Brigham’s Department of Preventive Medicine and VITAL’s principal investigator. ‘The fact that we were able to look at an expanded vitamin D metabolite profile and new biomarkers gave us unique insight into vitamin D availability and activity, and whether vitamin D metabolism might be impaired in some people and not in others,’ she added.
The researchers found that vitamin D supplementation raised most of the biomarkers related to vitamin D metabolism in study participants, regardless of their weight. However, these increases were much smaller in those with elevated BMI.
“We saw striking differences after two years, indicating a poor response to vitamin D supplementation with higher BMI,” said Tobias. ‘This may have clinical implications and potentially explain some of the observed differences in the effectiveness of vitamin D supplementation depending on obesity status,’ she noted.
“This study sheds light on why we see a 30-40% reduction in deaths from cancer, autoimmune and other diseases with vitamin D supplementation among those with a lower BMI, but minimal benefit in those with a higher BMI, suggesting that it is possible is to achieve population-wide benefits through more personalized vitamin D dosing. These nuances make it clear that there is more to the vitamin D story, Manson said.
The authors of the study call for further research on the potential benefits of vitamin D supplementation in preventing cancer and other diseases, and for BMI to be taken into account when assessing the health impact of the supplement.
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