As up to 50 million Americans can personally testify, autoimmune disorders (AD) defy easy treatment, but a new study from Brigham and Women’s Hospital, in Boston, offers hope that vitamin D3 supplementation can significantly reduce the risk of incurring these disorders in the first place. Researchers divided 25,871 older adults into four groups: the first took 2,000 IU of vitamin D3 daily; the second took 1,000 milligrams a day of marine omega-3 fatty acids (fish oil); the third took both D3 and fish oil; and a fourth was given a placebo. After two years, those that took vitamin D with or without the fish oil had a significantly lower rate of autoimmune diseases, such as rheumatoid arthritis, polymyalgia rheumatica, autoimmune thyroid disease and psoriasis, compared to the placebo group. While the fish oil alone didn’t lower AD risk, there was some evidence that it had an effect over time. “Autoimmune diseases are common in older adults and negatively affect health and life expectancy. Until now, we have had no proven way of preventing them, and now, for the first time, we do,” says first author Jill Hahn, Ph.D., an epidemiologist.

Vitamin D may also protect against COVID-19 severity, report Israeli researchers in the journal PLOS One. Examining the records of 1,176 patients admitted to a hospital with COVID-19-positive PCR tests, they found that those with a vitamin D deficiency (less than 20 nanograms per milliliter in their blood) were 14 times more likely to have a severe or critical case of COVID-19 than those with levels higher than 40 nanograms per milliliter. Mortality among patients with deficient vitamin D levels was 11 times higher than those with sufficient levels—25.6 percent compared to 2.3 percent.