Also known as: cholecalciferol, vitamin d, d3
Latest evidence update: 2026-11-01
Outcome estimates are derived from published research and represent population-level associations, not guaranteed individual results. Consult a healthcare professional before making decisions based on these estimates.
Recommended: 2000-5000 IU daily
Vitamin D3 is a form of Vitamin D. The studies above are specifically about Vitamin D3; broader vitamin d research differs in dose and bioavailability and lives on the parent page.
See all Vitamin Dresearch →ProtocolEngine provides general health information based on published research. This is not medical advice. Consult a healthcare professional before starting any supplement or health protocol.
May help reduce disease activity and progression in rheumatoid arthritis, with higher vitamin D levels associated with lower disease activity
Associated with reduced risk of multiple sclerosis and fewer disease relapses, with higher vitamin D levels linked to fewer brain lesions
May improve outcomes in inflammatory bowel disease by reducing inflammation markers and disease activity scores
Vitamin D deficiency is common in people with autoimmune thyroid disease and other autoimmune conditions, though supplementation effectiveness requires further study
Higher vitamin D levels are associated with lower COVID-19 mortality risk in hospitalized patients, though benefits in prevention remain unclear