Vitamin D is one of the most important nutrients for good health. It helps the body absorb calcium, which keeps bones and teeth strong.
It also supports muscles, the immune system, and many other important body functions.
Many people do not get enough vitamin D, especially during the colder months when there is less sunshine.
Our skin naturally makes vitamin D3 after being exposed to sunlight, but in winter people often spend less time outdoors, and the sun is not strong enough in many places to produce enough vitamin D. Because of this, millions of people take vitamin D supplements every year.
Many people believe that all vitamin D supplements work in the same way. However, new research suggests that this is not true.
Scientists have found important differences between two common forms of vitamin D supplements, known as vitamin D2 and vitamin D3. Although both can increase vitamin D levels, they do not appear to have the same effects inside the body.
The new study was carried out by researchers from the University of Surrey, the John Innes Center, and the Quadram Institute Bioscience. Their findings were published in the journal Nutrition Reviews.
The researchers examined evidence from many previous clinical studies comparing vitamin D2 and vitamin D3 supplements. They wanted to learn whether one form worked better than the other and whether either form had unexpected effects.
The results showed that people who took vitamin D2 supplements experienced a drop in their blood levels of vitamin D3. This was surprising because vitamin D3 is the form that the body naturally produces when sunlight reaches the skin. It is also widely considered to be the most effective form for improving vitamin D status.
In several of the studies, people taking vitamin D2 actually ended up with lower vitamin D3 levels than people who did not take any vitamin D supplement at all. This finding suggests that vitamin D2 may interfere with vitamin D3 in ways scientists are still trying to understand.
Dr. Emily Brown from the University of Surrey explained that vitamin D supplements are especially important during the months when sunlight is limited. However, her team found that vitamin D2 may reduce vitamin D3 levels, suggesting that vitamin D3 could be the better choice for most people.
The new findings also support earlier research. In a previous study published in Frontiers in Immunology, Professor Colin Smith and his colleagues found that vitamin D3, but not vitamin D2, appeared to activate an important immune defense known as the type I interferon signaling system.
This system helps the body respond to harmful bacteria and viruses before they can cause serious infections. While more research is needed, the results suggest that vitamin D3 may offer extra immune benefits beyond simply raising vitamin D levels.
Vitamin D deficiency is a common health problem around the world. People who are older, have darker skin, spend little time outdoors, or always cover their skin may have a greater risk of low vitamin D levels. Deficiency can weaken bones, increase the risk of fractures, cause muscle weakness, and may affect immune function.
Experts say choosing the most effective form of vitamin D could improve public health. Professor Martin Warren from the Quadram Institute said that using the best form of vitamin D in supplements and fortified foods may help reduce vitamin D deficiency.
Professor Cathie Martin from the John Innes Center also said that making plant-based vitamin D3 more widely available would allow more people, including those following vegetarian or vegan diets, to benefit.
Even though vitamin D3 appears to be the preferred option for most people, supplements are not one-size-fits-all. Individual health needs can differ depending on age, medical conditions, diet, and advice from a healthcare professional. People should always follow recommended doses because taking too much vitamin D can also be harmful.
Overall, this research provides stronger evidence that vitamin D3 is generally more effective than vitamin D2 for maintaining healthy vitamin D levels. Scientists will continue studying why the two forms behave differently and whether certain groups of people may benefit from one type over the other.
For now, people looking for a vitamin D supplement may want to discuss vitamin D3 with their doctor or pharmacist, particularly during the winter months when natural vitamin D production is low.
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