Many people take vitamin D pills to stay healthy, especially in winter when there is less sunlight. Vitamin D helps keep bones strong, supports muscles, and plays an important role in the immune system.
Our bodies can make vitamin D when sunlight touches the skin, but during colder months or in places with long winters, this natural process does not work as well. Because of this, millions of people rely on supplements to keep their vitamin D levels up.
However, new research shows that not all vitamin D supplements work in the same way. Scientists have discovered that one common type may not be as helpful as people think, and in some cases could even lower the level of the form of vitamin D that the body uses best.
Researchers from the University of Surrey, the John Innes Centre, and the Quadram Institute Bioscience studied two main types of vitamin D found in supplements. These are called vitamin D2 and vitamin D3.
Vitamin D3 is the type our skin makes from sunlight. It is also found in foods such as oily fish, egg yolks, and some fortified dairy products. Vitamin D2 usually comes from plant sources and fungi and is often used in vegetarian supplements.
Both types can raise vitamin D levels in the blood, so for many years they were thought to be almost the same. But the new study found an important difference.
When people took vitamin D2 supplements, their levels of vitamin D3 in the blood actually dropped. Vitamin D3 is the form that the body uses most easily, so lowering it may reduce some of the benefits people expect from taking supplements.
In several studies reviewed by the scientists, people who took vitamin D2 ended up with lower vitamin D3 levels than people who did not take any supplement at all. This surprising result suggests that vitamin D2 may interfere with vitamin D3 in the body. The research was published in the journal Nutrition Reviews.
The scientists explained that vitamin D supplements are still very important, especially between autumn and early spring when sunlight is weak. In countries such as the United Kingdom, people cannot make enough vitamin D from the sun during these months.
This is also true for people who spend most of their time indoors, cover their skin for cultural reasons, or use strong sun protection all the time.
Earlier research by the same team also found that vitamin D3 may help the immune system in ways that vitamin D2 does not.
Vitamin D3 appears to activate a key defense system in the body that helps fight viruses and bacteria. This system is part of how the body responds quickly when germs enter. Keeping vitamin D3 at a healthy level may therefore help reduce the risk of infections.
Vitamin D deficiency is common around the world. It has been linked to weak bones, tiredness, muscle pain, and a higher risk of illness. Older adults, people with darker skin, and those who rarely go outside are more likely to have low vitamin D. Because of this, choosing the most effective supplement could have a big impact on public health.
Experts say more research is needed to fully understand how vitamin D2 and D3 interact in the body. Still, the current evidence suggests that vitamin D3 may be the better choice for most people who need a supplement. Scientists are also working on plant-based sources of vitamin D3 so that it can be suitable for vegetarians and vegans as well.
For now, the message is simple. Vitamin D remains essential for good health, but the type you take matters. If you rely on supplements to stay healthy during the darker months, choosing vitamin D3 may give you stronger support for your bones and immune system.
If you care about nutrition, please read studies about the best time to take vitamins to prevent heart disease, and vitamin D supplements strongly reduce cancer death.
For more information about nutrition, please see recent studies about plant nutrient that could help reduce high blood pressure, and these antioxidants could help reduce dementia risk.
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