Vitamin D supplementation reduces autoimmune disease – but effect blunted by higher BMI

Vitamin D – an essential nutrient involved in many biological processes, most notably helping the body absorb minerals, such as calcium and magnesium – is known to regulate a wide array of genes involved in inflammation and immunity.

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

"This study sheds light on why we’re seeing 30-40% 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 personalised dosing of vitamin D,” said senior author JoAnn E Manson, chief of Brigham’s Division of Preventive Medicine and principal investigator of the trial.

Anti-inflammatory approaches to manage psoriasis

It follows earlier research from the same trial that found vitamin D supplementation for five years, with or without omega-3 fatty acids, reduced autoimmune disease by 22%.

One such disease is psoriasis, a chronic condition that typically presents with red, scaly, itchy patches on the skin. It involves inflammation at a systemic level and is associated with gut dysbiosis.

Other nutritional interventions that have been studied for their effects on psoriasis include antioxidants, curcumin, and probiotics. It is thought that these may have an effect because they modulate the microbiome or exert anti-inflammatory effects.

Personalised nutrition is another strategy that has been suggested for symptom management.

Anti-inflammatory approaches have been in the spotlight thanks to celebrities such as Kim Kardashian, who has been vocal about having the condition: last year, she shared on her sister Kourtney’s lifestyle blog, Poosh, that a plant-based diet has been key to keeping her symptoms at bay.

Vitamin D correlated with positive effects on health outcomes

The study findings, which were published in JAMA Network Open, are an analysis of data from the VITAL trial, a large-scale randomised study led by researchers at Brigham and Women’s Hospital in Boston, Massachusetts.

Involving more than 25,800 participants, including men over the age of 50 and women over the age of 55, the trial is investigating whether taking vitamin D or omega-3 supplements can reduce the risk of developing cancer, heart disease, or stroke.

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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 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, an associate epidemiologist in Brigham’s Division of Preventive Medicine. “There seems to be something different happening with vitamin D metabolism at higher body weights.”

Expanded metabolite and biomarker profile gives unique insights

The new study aimed to investigate this correlation. The researchers analysed data from 16,515 participants from the original trial who provided blood samples at baseline (before randomisation to vitamin D), as well as 2,742 with a follow-up blood sample taken after two years.

They measured levels of total and free vitamin D, as well as other novel biomarkers for vitamin D, such as its metabolites, calcium, and parathyroid hormone, which helps the body utilise the nutrient.

“Most studies like this focus on the total vitamin D blood level,” said Manson. “The fact that we were able to look at this expanded profile of vitamin D metabolites and novel biomarkers gave us unique insights into vitamin D availability and activity, and whether vitamin D metabolism might be disrupted in some people but not in others.”

The authors conclude that the findings are a call to action for the research community to continue exploring the potential benefits of vitamin D supplementation for preventing disease.