Popular Vitamin D Supplement Has “Previously Unknown” Negative Effect, Study Finds

A new meta-analysis suggests vitamin D2 supplements may lower circulating vitamin D3 levels.

The review of randomized controlled trials indicates vitamin D3 may better support overall vitamin D status and immune-related pathways.

Researchers linked vitamin D3 more strongly than D2 to type I interferon signaling, an important immune response pathway.

The findings challenge the idea that vitamin D2 and D3 are interchangeable and may influence supplement advice for bone and immune health.