Vitamin D supplements are often seen as a simple way to support bone strength, immunity, and overall health. Many people rely on them, especially during the colder months when the body cannot naturally produce enough from sunlight. However, not all supplements have the same effect on the body’s vitamin balance, and one option may actually reduce the levels of the form most effective for health.
Scientists have long distinguished between the two main types of supplements available: vitamin D2 and vitamin D3. While both are taken to meet daily nutritional needs, new findings reveal that choosing one form could undermine the body’s ability to maintain healthy concentrations of the other, particularly the type that naturally comes from sunlight exposure.
Does a common vitamin D supplement really lower D3 levels?
A recent investigation has shown that vitamin D2, one of the most widely consumed forms, can lead to a measurable decline in vitamin D3 levels. The study was conducted by researchers from the University of Surrey in collaboration with the John Innes Center and the Quadram Institute Bioscience. Their work was published in the journal Nutrition Reviews.
Emily Brown, Ph.D., lead researcher from the University of Surrey’s Nutrition, Exercise, Chronobiology & Sleep Discipline, explained that although supplements are crucial when sunlight is scarce, vitamin D2 comes with an unexpected effect: it decreases vitamin D3 in the body. She emphasized that this was previously unknown and suggested that, depending on individual needs, vitamin D3 supplementation could be more effective than vitamin D2.
The findings are based on a meta-analysis of randomized controlled trials, which consistently showed a drop in vitamin D3 concentrations among people who took vitamin D2 compared with those who did not. In several cases, the levels fell even lower than in participants who were not supplementing at all.
Why the difference between D2 and D3 matters
Vitamin D3 is the form the body naturally produces through sunlight and the one most efficiently used to maintain overall vitamin D status. By contrast, vitamin D2, while still a form of the nutrient, does not appear to work the same way inside the body. This difference is especially relevant for people relying on supplements to meet daily requirements.
The public health perspective
Professor Martin Warren, Chief Scientific Officer at the Quadram Institute, stressed that vitamin D deficiency remains a major public health issue, particularly in winter. He explained that addressing this gap with the most effective form of supplementation or food fortification is essential to protect population health.
The researchers agree that more work is needed to explore the distinct roles of vitamin D2 and D3. Understanding these differences will be key in deciding whether vitamin D3 should be prioritized as the primary supplement for most people, always considering individual health needs.
For now, the evidence points toward one clear conclusion: not all vitamin D supplements act the same way, and choosing wisely could make a significant difference in maintaining the body’s natural defenses, nutrient balance, and overall long-term health outcomes effectively.