Not all forms of vitamin D work the same way inside the body.
D2 supplements may actually reduce levels of vitamin D3, the form of vitamin D that the body naturally produces from sunlight.
Vitamin D supplements generally come in two forms: vitamin D2 and vitamin D3.
While both are used to help raise vitamin D levels, researchers say they may affect the body differently.
Vitamin D3 is considered the more effective form because it is the version naturally created in the skin when exposed to sunlight.
It is also widely regarded as the form that does a better job of maintaining healthy vitamin D status.
New Analysis Reveals Unexpected Effect
The findings were published in Nutrition Reviews after researchers examined data from multiple randomized controlled trials.
After reviewing the studies, the team discovered that participants taking vitamin D2 supplements often experienced a decline in their vitamin D3 levels compared to people who were not taking vitamin D2.
In several cases, vitamin D3 concentrations fell below those seen in control groups.
Researchers say this drop in vitamin D3 was an unexpected finding and highlights an important difference between the two supplement types.
Why Researchers Recommend Vitamin D3
Vitamin D supplementation remains important, particularly between October and March in the UK when sunlight is not strong enough for the body to produce adequate vitamin D naturally.
However, the research suggests that vitamin D2 may have an unintended effect by lowering the body’s stores of vitamin D3.
The study findings indicate that vitamin D3 could be the better option for most people, although individual health needs should always be considered.
The study adds to earlier research that found vitamin D2 and vitamin D3 may not provide identical immune system benefits.
Researchers found that vitamin D3 appears to activate the body’s type I interferon signaling pathway, an important part of the immune response that helps defend against viruses and bacteria during the early stages of infection.
Scientists believe maintaining healthy vitamin D3 levels may strengthen the body’s natural defenses and help reduce the ability of harmful microbes to gain a foothold.
Although the findings point toward advantages for vitamin D3, researchers say more studies are needed to fully understand the biological differences between the two forms.
Future research could help determine whether vitamin D3 should become the preferred first-line supplement recommendation in more situations.
