New Research on Vitamin D Supplements Raises Questions
A recent meta-analysis is questioning what we’ve long assumed about vitamin D supplements.
Researchers from the University of Surrey, the John Innes Centre, and Quadram Institute Bioscience are diving into the debate between vitamin D2 and vitamin D3. Surprisingly, their findings imply that these two types may not be as interchangeable as once thought—and in some cases, one could potentially counteract the other.
Vitamin D is a go-to for many looking to support bone health and boost immune function, particularly when sunlight is scarce. In the U.S., the general recommendation for adults is about 15 micrograms (600 IU) daily, though individual needs can vary. Yet, as this study shows, not all supplements affect the body in the same way.
What’s the Difference Between D2 and D3?
Vitamin D comes mainly in two forms. D3 is produced naturally in the skin with sun exposure and is also found in foods like fatty fish and egg yolks. On the other hand, vitamin D2 is derived from plants—commonly mushrooms exposed to UV light—and has often been considered a suitable alternative.
However, the recent study published in Nutrition Reviews indicates that taking vitamin D2 may actually reduce the body’s levels of vitamin D3. Researchers scoured randomized controlled trials and discovered that those who took D2 supplements frequently exhibited lower levels of D3, sometimes dropping below those seen in people not taking any supplements at all.
Insights on the Interaction Between D2 and D3
This surprising interaction might shed light on why some people don’t experience the same benefits from different vitamin D forms.
Emily Brown, a PhD Research Fellow and the lead author, noted that while vitamin D supplements are important—especially in the UK from October to March when sunlight exposure is limited—they found that D2 could actually lower D3 levels in the body. This effect was previously unknown. She suggests that, considering individual circumstances, D3 supplements may be more advantageous for most people compared to D2.
The study adds to a growing body of evidence hinting that D3 plays a more active role in supporting the immune system. Earlier research indicated that D3, unlike D2, helps activate key immune responses against viral infections.
Health Implications in the Real World
Low vitamin D levels have been linked to weakened immune responses and increased infection risk. If D2 is not as effective at raising the body’s overall vitamin D and also lowers D3, it might not offer the same protective benefits.
At the same time, issues of accessibility and dietary choices persist. D3 has traditionally been animal-derived, but plant-based options made from lichen are starting to emerge.
Professor Cathie Martin emphasizes the need for making plant-based vitamin D3 widely available in the UK.
Future studies will look into how these forms perform across various populations and whether it might be necessary to shift recommendations towards prioritizing D3.
Professor Martin Warren, Chief Scientific Officer at Quadram Institute, mentioned that vitamin D deficiency is a significant public health issue, especially during the winter months when many are affected. This collaborative effort is aligned with the mission of promoting better health through diet, aiming to enhance the nutrient density of our food. Addressing the matter with the most effective vitamin D supplementation method is key for national health.
