Prolonged vitamin D intake reduces autoimmune disease risk in older adults up to 39%

27 Jan 2022 --- Vitamin D may significantly reduce the chances of developing an autoimmune disease (AD) in older adults, with mixed results for omega 3s from fish oil. The findings are “of clinical importance,” given there are no other known effective therapies to reduce rates of AD. 

Researchers at Brigham and Women’s Hospital found that US adults over 50 taking 2,000 IU per day of vitamin D had a 22% reduction in AD over a 5.3 year trial period compared to placebo.

“This is the first direct evidence we have that daily supplementation may reduce the incidence,” says senior author Dr. Karen Costenbader of the Brigham’s Division of Rheumatology, Inflammation and Immunity. 

“Until now, we have had no proven way of preventing [AD], and now, for the first time, we do.” 

Fishy outcomes?
Study participants who took 1 g of omega 3s daily – either in combination with vitamin D or alone – witnessed a 15% reduction in AD incidence compared to the placebo groups. 

Preclinical studies have suggested vitamin D and omega 3s may have beneficial effects on autoimmune diseases.This result was not considered significant unless researchers included “probable cases” data. Probable case participants had evidence of AD but lacked proper documentation. 

Including them showed a reduced incidence of developing AD with fish oil supplementation alone by a significant 18%. 

A subgroup analysis also reveals that the beneficial effect of omega 3 fatty acids on autoimmune disease prevention was greater among those with a family history of autoimmune disease. 

Supplements take time
The study authors write that while fish oils had no significant impact on AD risk over the total 5.3-year period, their effect increased over time. 

This was also the case for vitamin D alone and in combination with omega 3s. 

When only the last three years of the trial were considered, the vitamin D group had 39% fewer confirmed cases than the placebo, compared to 22% fewer cases when examining the whole period. 

Moreover, combined vitamin D and omega 3s supplementation decreased autoimmune disease by about 30% versus placebo alone when looking at the last three years of the study. This is in contrast to a 15% reduction over the entire 5.3-year period. 

Researchers note that all study participants were older and results may not be generalizable for younger populations.Scale of these diseases
AD, such as rheumatoid arthritis, polymyalgia rheumatica, autoimmune thyroid disease and psoriasis, are a leading cause of morbidity and mortality as people age. 

“AD is common in older adults and negatively affects health and life expectancy,” says Jill Hahn, lead author on the study and post-doctoral fellow at the Brigham. 

However, preclinical studies have hinted that supplements, including vitamin D and omega 3 fatty acids, may have beneficial effects.

To further investigate, researchers behind the recent BMJ-published study used data from the large-scale vitamin D and Omega-3 Trial (VITAL), which followed participants for approximately five years.

Tapping a larger data set
VITAL is a randomized, double-blind, placebo-controlled research study of 25,871 men (age 50 and older) and women (age 55 and older) across the US, conducted to investigate whether taking daily dietary supplements of vitamin D3 (2,000 IU) or omega 3 fatty acids (1 g) could reduce the risk for developing cancer, heart disease and stroke in people who do not have a prior history of these illnesses. 

Participants were randomized to receive either vitamin D with an omega 3 fatty acid supplement; vitamin D with a placebo; omega 3 fatty acid with a placebo; or placebo only.

Prior to the launch of VITAL, investigators determined that they would also look at rates of AD among participants as part of an ancillary study.

“Given the benefits of vitamin D and omega 3s for reducing inflammation, we were particularly interested in whether they could protect against autoimmune diseases,” says Dr. JoAnn Manson, study co-author and director of the parent VITAL trial at the Brigham.

For future investigation
The VITAL study included a large and diverse sample of participants. However, all participants were older and the researchers conclude their results may not be generalizable to younger individuals who experience AD earlier in life. 

The trial also only tested one dose and one formulation of each supplement. The researchers note that longer follow-up may be more informative to assess whether the effects are long-lasting.

“We look forward to honing and expanding our findings and encourage professional societies to consider these results and emerging data when developing future guidelines for the prevention of autoimmune diseases in midlife and older adults,” concludes Costenbader. 

Vitamin D has come fully in the spotlight since a waterfall of studies have investigated its link with COVID-19 outcomes. 

Omega 3 DHA has also been investigated recently for its impact on the immune system, including its ability to reduce the risk of preterm birth via modulation of the mother’s inflammatory immune response.

By Missy Green