Vitamin D2 supplements may impact bone and immune health by lowering D3 levels, study warns

A new review and meta-analysis reveals that vitamin D2 supplements may lower vitamin D3 levels — an essential nutrient for bone and immune health — than non-supplement users.

The publication in Nutrition Reviews suggests prioritizing vitamin D3 supplements for people, especially those with vitamin D deficiency. 

“The meta-analysis reported here is, to the knowledge of the authors, the first to quantify the effect of vitamin D2 supplementation on vitamin D3 concentrations,” reads the paper.

The study is especially relevant for people in the UK, for instance, during winter, when natural sunlight synthesis is inadequate, say researchers from UK-based University of Surrey, John Innes Centre, and Quadram Institute Bioscience. 

“Vitamin D supplements are important, especially between October and March, when our bodies cannot make vitamin D from sunlight in the UK,” says lead researcher Emily Brown, Ph.D., research fellow at the University of Surrey.

“However, we discovered that vitamin D2 supplements can actually decrease levels of vitamin D3 in the body, which is a previously unknown effect of taking these supplements. This study suggests that, subject to personal considerations, vitamin D3 supplements may be more beneficial for most individuals than vitamin D2.”

Vegan vitamin D3 accessibility

The researchers hope that their review will aid future policies regarding vitamin D3 use over vitamin D2 supplements. They state that literature shows that vitamin D3 raises the total 25(OH)D status better than vitamin D2.

“Vitamin D2 supplement production would, of course, remain necessary to facilitate availability for personal requirements, as nearly all vitamin D3 supplements are derived from animal sources and are therefore not applicable to vegans,” the report warns. 

“However, the production and prescription of vitamin D3 as a first-line recommendation may be a useful policy to implement due to the potential detrimental influence vitamin D2 supplements may have upon serum 25(OH)D3 status.”

Professor Cathie Martin, group leader at the John Innes Centre, adds: “This meta-analysis highlights the importance of ensuring plant-based vitamin D3 is accessible in the UK.”

Vitamin D3 for immune support

The review supports previous research by Professor Colin Smith at the University of Surrey, finding that vitamins D2 and D3 do not have the same function in supporting immune function.

“We have shown that vitamin D3, but not vitamin D2, appears to stimulate the type I interferon signalling system in the body — a key part of the immune system that provides a first line of defence against bacteria and viruses,” he says. “Thus, a healthy vitamin D3 status may help prevent viruses and bacteria from gaining a foothold in the body.”

The University of Surrey suggests that future research should examine whether vitamin D3 should be the first-line choice of vitamin D supplementation.

Professor Martin Warren, chief scientific officer at the Quadram Institute, comments: “This collaborative research effort aligns well with the Quadram Institute’s mission to deliver healthier lives through food innovation to enhance the nutrient density of the food we eat.”

“Tackling this with the most effective form of vitamin D supplementation or fortification is of the utmost importance to the health of the nation.”