Vitamin D2 Supplements May Reduce Vitamin D3 Levels

Taking vitamin D2 supplements may decrease the body's levels of vitamin D3, according to new research. Vitamin D3 is the form of vitamin D that the human body produces naturally from sunlight. It is also the form the body uses most effectively to raise overall vitamin D levels.

The study, published in *Nutrition Reviews*, analyzed data from multiple randomized controlled trials. Researchers found that vitamin D2 supplementation led to a reduction in vitamin D3 concentrations. In many cases, vitamin D3 levels dropped below those of control groups who did not take vitamin D2 supplements.

Emily Brown, a research fellow and lead researcher from the University of Surrey, stated that this effect of vitamin D2 supplements was previously unknown. She suggested that vitamin D3 supplements might be more beneficial for most individuals.

This research supports an earlier study published in *Frontiers in Immunology*. That study indicated that vitamin D2 and vitamin D3 do not play identical roles in immune function. Vitamin D3 appears to modify the immune system in a way that could strengthen the body's defenses against viruses and bacteria.

Professor Colin Smith from the University of Surrey explained that vitamin D3, but not vitamin D2, stimulates the type I interferon signaling system. This system is a key part of the immune system's initial defense against pathogens. A healthy vitamin D3 status may help prevent infections.

Further research is needed to fully understand the different functionalities of vitamin D2 and D3. This understanding will help determine if vitamin D3 should be the primary choice for vitamin D supplementation.