New research from the University of Surrey, John Innes Centre and Quadram Institute reveals that vitamin D2 supplements may actually reduce the body’s levels of vitamin D3.
Many people take vitamin D supplements to support their bone and immune health and meet the UK government recommendation of 10 micrograms (µg) each day, especially during the winter months.
There are two forms of vitamin D supplements available: vitamin D2 and vitamin D3.
Vitamin D3 is the more effective form of vitamin D, associated with stronger bones and better immune health.
It is the form our bodies naturally produce from sunlight and use most effectively to raise overall vitamin D levels.
The findings suggest vitamin D3 could be a more beneficial option for most people, especially in winter months when the risk of deficiency is at its highest.
Many people take vitamin D supplements to support their bone and immune health and meet the UK government recommendation of 10 µg each day, especially during the winter months.
The study, published in Nutrition Reviews, analysed data from randomised controlled trials and found that vitamin D2 supplementation resulted in a reduction in vitamin D3 levels, compared to those not taking a vitamin D2 supplement.
In many of the studies, the vitamin D3 levels went lower than in the control group.
Emily Brown, PhD, lead researcher and fellow at the University of Surrey, said: "Vitamin D supplements are important, especially between October and March, when our bodies cannot make vitamin D from sunlight in the UK."
"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."
Professor Cathie Martin, group leader at the John Innes Centre, said: “This meta-analysis highlights the importance of ensuring plant-based vitamin D3 is accessible in the UK.”
The findings support earlier research by Professor Colin Smith (University of Surrey), published in Frontiers in Immunology, showing vitamin D2 and D3 play different roles in immune function.
Vitamin D3 has a modifying effect on the immune system that could fortify the body against viral and bacterial diseases.
Professor Colin Smith said: “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."
"Thus, a healthy vitamin D3 status may help prevent viruses and bacteria from gaining a foothold in the body.”
Further research into the different functionalities of vitamins D2 and D3 should be a priority in deciding whether vitamin D3 should be the first-line choice of vitamin D supplement, subject to individual requirements.
Professor Martin Warren, Chief Scientific Officer at the Quadram Institute, said: "Vitamin D deficiency represents a significant public health concern, especially during the winter months, with significant deficiency across the UK population."
"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."