You probably take vitamin D without thinking twice. It is one of those nutrients we all hear about, especially when the days get shorter and sunlight feels scarce. Many people rely on supplements to maintain their vitamin D levels, trusting that all forms work in the same way. Yet, recent research suggests this might not be the case.
Scientists have discovered that not all vitamin D supplements deliver the same results. The two primary forms, D2 and D3, differ in how the body absorbs and uses them. Evidence now shows that D3, the form naturally produced through sunlight exposure, may be significantly more effective in supporting immunity and overall health. So before you reach for your next bottle, it may be worth asking yourself whether you are taking the right form of vitamin D.
What Exactly Is Vitamin D and Why Do We Need It?
Vitamin D is a fat-soluble nutrient that supports many essential processes in the body. It helps regulate calcium and phosphate levels, which are needed to keep bones, muscles, and teeth healthy. Without enough vitamin D, calcium absorption decreases, increasing the risk of weakened bones and conditions such as osteoporosis.
Our bodies can produce vitamin D when the skin is exposed to sunlight, but in places where sunlight is limited during autumn and winter, it can be difficult to maintain sufficient levels. That is why the HSE recommends taking 10 micrograms of vitamin D daily, especially during the colder months.
Beyond bone health, vitamin D also contributes to normal immune system function and muscle strength. Studies suggest that people with adequate vitamin D levels tend to have better resistance against infections and may even experience improved mood and energy. With such a wide range of benefits, maintaining the right vitamin D level is key to overall wellbeing. If you are wondering whether you might be low in vitamin D, you can read our article on 6 signs you might be deficient in vitamin D
D2 vs D3: Not All Vitamin D Is the Same
Where They Come From
When you look at a supplement label, it often just says “vitamin D.” There are two distinct forms of this nutrient: vitamin D2 and vitamin D3. Although they sound similar, the body handles them in very different ways.
Vitamin D2 is found in certain plants and fortified foods, while vitamin D3 occurs naturally in animal sources and is produced in the skin when exposed to sunlight. For many years, both were thought to have the same benefits, but new research challenges this assumption.
How the Body Uses Them Differently
A recent study published in Nutrition Reviews by scientists from the University of Surrey, the John Innes Centre and the Quadram Institute Bioscience found that supplements containing vitamin D2 can reduce levels of vitamin D3 in the body. Participants who took vitamin D2 showed lower concentrations of vitamin D3 compared with those who took vitamin D3 or no supplement at all.
This matters because vitamin D3 is the form that your body uses most efficiently. It is more effective at maintaining healthy vitamin D levels and plays an important role in supporting the immune system. Another paper published in Frontiers in Immunology, led by Professor Colin Smith from the University of Surrey, also showed that vitamin D3 helps regulate immune responses and strengthens the body’s defences against bacteria and viruses, while vitamin D2 does not have the same impact.
In simple terms, both are called vitamin D, but your body clearly benefits more from vitamin D3.
What the Research Tells Us About Immunity
Vitamin D has long been known for its role in keeping bones strong, but its connection to immunity is now gaining much more attention. The study published in Nutrition Reviews by the University of Surrey team highlights that vitamin D3 does more than maintain bone density. It also helps regulate the genes involved in immune defence.
Researchers found that vitamin D3 activates key mechanisms that strengthen the body’s first response to infection. This includes enhancing the function of immune cells that act as the body’s initial line of protection against harmful bacteria and viruses. In contrast, vitamin D2 did not appear to trigger the same immune activity, suggesting that its role in supporting immune health may be limited.
These findings are consistent with earlier work published in Frontiers in Immunology, which showed that vitamin D3 contributes to better immune regulation and may help the body recover more efficiently after viral or bacterial infections. While both forms are still considered safe, this growing evidence suggests that choosing vitamin D3 could provide broader support for immune balance and overall wellbeing.
Choosing the Best Vitamin D Supplement
Once you know the difference between vitamin D2 and D3, choosing the right supplement becomes much easier. Most evidence now points to vitamin D3 as the form that your body recognises and uses most effectively. When comparing options, it is worth checking the label to ensure that the supplement contains vitamin D3 rather than D2.
At Sona, all our vitamin D supplements are formulated with vitamin D3, the same form your body naturally produces when exposed to sunlight. You can choose from different strengths depending on your needs, such as 400 IU for general daily support, 1000 IU for maintenance, or 2000 IU for higher supplementation. Sona also offers a D3 + K2 formula for those who want extra support for bone and cardiovascular health, as well as gentle, age-appropriate options for babies aged 0 to 1 year and children aged 1 to 12 years. This way, every member of the family can maintain healthy vitamin D levels all year round.
Sona’s vitamin D3 range is available in convenient forms such as tablets, capsules, and oral sprays, making it easy to find the product that fits your lifestyle. You can explore our vitamin D range. If you are unsure which strength is right for you, consider your age, diet and how much time you spend outdoors. During the darker months, when sunlight exposure is low, a daily vitamin D3 supplement can help maintain healthy levels and support immunity throughout the year.
The Final Say
Vitamin D influences so much more than we realise, from helping to keep bones strong to supporting the immune system and energy levels. The good news is that maintaining healthy levels can be simple. Spending time outdoors when possible, eating vitamin D–rich foods and taking a daily supplement can all help keep your body in balance.
For most people, vitamin D3 is the most effective form to maintain optimal levels throughout the year. So, whether it is sunshine, diet, or a trusted supplement from Sona’s vitamin D range, giving your body the right form of vitamin D can make all the difference.
References;
University of Surrey, John Innes Centre and Quadram Institute Bioscience (2024). The vitamin D mistake weakening your immunity. Published in Nutrition Reviews. Available at: https://www.sciencedaily.com/releases/2025/10/251004092911.htm
Smith, C. et al. (2022). Differences in the effects of vitamin D2 and vitamin D3 on the human immune system. Frontiers in Immunology. Available at: https://www.surrey.ac.uk/news/vitamin-d3-concentrations-are-lowered-common-vitamin-d-supplement