Vitamin D supplementation for five years, with or without omega-3 fatty acids, reduced autoimmune diseases such as rheumatoid arthritis and psoriasis by 22%, according to the findings of a new study published in the British Medical Journal (BMJ). Omega-3 fatty acid supplementation with or without vitamin D reduced the autoimmune disease rate by 15%, which was not statistically significant. Both treatment arms showed larger effects than the reference arm (vitamin D placebo and omega-3 fatty acid placebo).