Vitamin D is one of the most popular dietary supplements in the world. Many people take it to keep their bones strong, support their muscles, and help their immune system work properly.
During the colder months, when there is less sunlight, vitamin D supplements become even more important because the body cannot make enough of this vitamin from sunlight alone.
However, new research suggests that choosing the right type of vitamin D may matter more than many people realize.
Scientists from the University of Surrey, the John Innes Centre, and the Quadram Institute Bioscience have discovered that two common forms of vitamin D do not work in the same way. Their findings were published in the journal Nutrition Reviews.
There are two main forms of vitamin D found in supplements: vitamin D2 and vitamin D3. Both can increase the total amount of vitamin D in the body, but the new study found an important difference between them. People who took vitamin D2 supplements often experienced a drop in their vitamin D3 levels.
Vitamin D3 is the form that the body naturally makes when the skin is exposed to sunlight. It is also widely believed to be the form that raises vitamin D levels more effectively. Surprisingly, several of the studies reviewed showed that people taking vitamin D2 ended up with lower vitamin D3 levels than people who did not take any vitamin D supplement at all.
The researchers carefully examined evidence from many previous clinical studies to better understand how these two forms affect the body. Their analysis showed that although vitamin D2 can increase overall vitamin D, it may also reduce the amount of vitamin D3 that is circulating in the blood. This unexpected effect could reduce some of the benefits people hope to gain from supplementation.
Lead researcher Dr. Emily Brown from the University of Surrey said vitamin D supplements remain very important, especially during the months when sunlight is limited. However, she explained that the findings suggest vitamin D3 may be the better choice for most people because vitamin D2 appears to lower the body’s natural vitamin D3 levels.
The new research also supports earlier work from the University of Surrey that looked at the immune system. In a previous study published in Frontiers in Immunology, researchers found that vitamin D3, but not vitamin D2, appeared to activate an important part of the immune system known as type I interferon signaling. This system helps the body defend itself against viruses and bacteria before infections become established.
Vitamin D deficiency remains common in many countries, especially during winter when people spend more time indoors and receive less sunlight. Health experts believe improving vitamin D levels through supplements or fortified foods could benefit many people. Researchers also noted that developing more plant-based sources of vitamin D3 could make this more suitable for people following vegetarian or vegan diets.
The scientists say more studies are still needed to fully understand why vitamin D2 and vitamin D3 behave differently inside the body. Future research may also identify whether certain groups of people could benefit more from one form than the other.
For now, the evidence points to vitamin D3 as the preferred option for most healthy adults who need a supplement.
Anyone thinking about starting or changing a vitamin D supplement should discuss it with their healthcare provider, especially if they have medical conditions or take other medicines. Choosing the most effective form of vitamin D may be a simple step toward supporting stronger bones, a healthier immune system, and better overall health.
If you care about nutrition, please read studies about the power of beetroot juice, and the risks of mixing medications with dietary supplements.
For more health information, please see recent studies about how to boost iron intake: natural solutions for anemia, and results showing vitamin K may lower your heart disease risk by a third.
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