TL;DR
Turn your wind-down time into listening time
- Thousands of audiobooks, podcasts and originals
- Listen on your phone, tablet or Echo — also offline
- Cancel anytime
A 2025 review found that people taking vitamin D2 had lower concentrations of 25-hydroxyvitamin D3, a form measured to assess vitamin D status. The researchers say this does not show that D2 is harmful or that it removes vitamin D from the body; the health significance of the drop remains unknown.
A review of clinical trials published in 2025 found that people taking vitamin D2 had lower blood concentrations of 25-hydroxyvitamin D3, a marker used to assess vitamin D status. The finding suggests the two supplement forms may not be interchangeable in their effects, but researchers say it does not establish that D2 is harmful or explain whether the observed change affects health.
Researchers from the University of Surrey, the John Innes Centre and Quadram Institute Bioscience brought together evidence from 20 studies; 11 provided data for the main meta-analysis. Compared with people who did not receive D2, participants who took it had significantly lower concentrations of 25-hydroxyvitamin D3. Depending on the analysis, the average difference was about 9 to 18 nanomoles per liter.
The result concerns one form of vitamin D measured in the blood, not total vitamin D alone. D2, also called ergocalciferol, can raise the D2-derived marker 25-hydroxyvitamin D2. The study therefore does not show that D2 simply depletes vitamin D overall, nor that people taking it necessarily experience harm. The researchers identified a change in the balance of measured forms; the cause and health consequences remain unsettled.
Vitamin D3, or cholecalciferol, is the form produced in human skin after exposure to ultraviolet B radiation. The U.S. National Institutes of Health says D3 tends to raise vitamin D levels more and keep them elevated longer than D2. D2 is often made from fungi or yeast, while supplements can also contain animal-free D3 derived from sources such as lichen.
How the Finding Could Affect Supplement Choices
The review could matter to people choosing supplements because D2 and D3 are often presented as alternative ways to obtain the same nutrient. Its results add evidence that the forms may behave differently in the body, including in their effects on blood vitamin D markers. The authors said D3 may be more beneficial for most people, subject to individual considerations, but the review does not establish that everyone should change products.
Vitamin D helps the body absorb calcium and supports bone health, as well as playing roles in muscle, nerve and immune function. Those functions make vitamin D status relevant to health, but they do not demonstrate that the D2-associated reduction in 25-hydroxyvitamin D3 causes a specific condition or changes clinical outcomes. The study measured the relationship between supplement use and vitamin D forms; it did not establish a treatment recommendation.
The choice may also have practical relevance for people seeking plant-based products. Traditional D3 supplements have often used lanolin from sheep’s wool, while lichen-derived D3 offers an animal-free option. The study’s findings are not a reason to stop prescribed or recommended supplements without consulting a qualified health professional.
Vitamin D3 supplements plant-based
As an affiliate, we earn on qualifying purchases.
As an affiliate, we earn on qualifying purchases.
What the Review Examined
After vitamin D enters the body, the liver converts it into 25-hydroxyvitamin D. Clinicians commonly measure this substance in blood tests to estimate vitamin D status. D2 produces a D2-derived version, and D3 produces a D3-derived version. The review focused on evidence that D2 supplementation was linked to a decline in the D3-derived form.
The researchers gathered results from randomized controlled trials, rather than reporting one new trial. Their meta-analysis compared findings across studies, with 11 of the 20 included studies contributing data to the main analysis. The reported reduction varied depending on how the data were analyzed, a reason to keep the estimated range attached to the result rather than treat it as one fixed effect for every person.
In the UK, public guidance advises people to consider taking 10 micrograms of vitamin D daily during darker months, when sunlight is generally too weak for skin to make enough. That advice is background to the research, not a finding of the meta-analysis. The study did not test whether changing supplement form improves health outcomes.
““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.””
— Emily Brown, lead researcher and research fellow at the University of Surrey
As an affiliate, we earn on qualifying purchases.
Health Effects Remain Unresolved
The review does not explain definitively why D2 supplementation was associated with lower 25-hydroxyvitamin D3. One possibility proposed by researchers is that the body changes how quickly it breaks down and removes vitamin D metabolites as their concentrations rise. That mechanism remains a hypothesis, not a confirmed explanation.
It is also unclear whether the measured reduction is large enough to affect health, whether it persists over time, or whether it has different implications for people with different starting vitamin D levels. The supplied research does not establish that the change causes illness, reduces overall vitamin D status, or changes rates of infection or other clinical outcomes.
Separate research reported differences in blood gene activity after D2 and D3 supplementation, including a D3-associated signal involving type I interferon. That finding does not prove that D3 prevents viruses or bacteria from causing illness. Immune signaling results should not be treated as evidence of a demonstrated protective effect.
Lichen-derived Vitamin D3 capsules
As an affiliate, we earn on qualifying purchases.
As an affiliate, we earn on qualifying purchases.
Further Research Must Test Health Outcomes
The immediate next step for researchers is to clarify how D2 and D3 affect one another and whether changes in their blood markers translate into meaningful health differences. Studies that track both vitamin D forms over time and examine clinical outcomes could help answer questions the review leaves open. The supplied report does not identify a specific upcoming trial or publication date.
For readers, the findings may prompt questions about supplement form, but they do not establish a universal switch from D2 to D3. People who are considering changing a supplement, or who take vitamin D for a medical reason, should discuss that decision with a qualified health professional. Current guidance and personal circumstances remain relevant while the evidence develops.
As an affiliate, we earn on qualifying purchases.
Key Questions
What did the 2025 review find about vitamin D2?
Across the studies included in the main analysis, taking vitamin D2 was associated with lower blood concentrations of 25-hydroxyvitamin D3 compared with not receiving D2. The average reduction was estimated at about 9 to 18 nanomoles per liter, depending on the analysis.
Does the finding mean vitamin D2 is harmful?
No. The review found a change in a D3-derived blood marker; it did not show that D2 is harmful, removes all vitamin D from the body, or causes illness. The health significance of the association is still unclear.
Are vitamin D2 and D3 the same?
They are different forms of vitamin D. Both can contribute to vitamin D status, but official U.S. guidance says D3 tends to raise blood vitamin D levels more and maintain them for longer than D2. The review adds evidence that their effects on measured forms may differ.
Should I switch from D2 to D3?
The review does not establish that everyone should switch. Supplement needs depend on individual circumstances, and people considering a change—especially those taking supplements for a medical reason—should consult a qualified health professional.
Is plant-based vitamin D3 available?
Yes. D3 has traditionally often been made using lanolin from sheep’s wool, but animal-free products derived from sources such as lichen are available.
Source: rss
Columbus Day / Indigenous Peoples' Day Picks
long weekend sales
As an affiliate, we earn on qualifying purchases.
