How taking the wrong vitamin D supplement can harm your immune system?

learn why choosing the right vitamin d supplement is crucial for protecting your immune system and overall health.(Image: Pexels)

As the cold creeps in and sunshine becomes a rare guest, many of us instinctively reach for vitamin D supplements to beat the winter blues and support our immune systems. But new research from the University of Surrey reveals a surprising twist—we might be taking the wrong kind. Instead of helping, vitamin D2 may actually reduce the levels of vitamin D3, the body’s most effective defence-boosting form. It means, it’s time to rethink your daily dose.

For years, taking a vitamin D supplement has been a staple of winter wellness, especially with the UK government recommending 10 micrograms per day during the darker months. But not all vitamin Ds are created equal. In a recent study published in Nutrition Reviews, researchers discovered that taking vitamin D2 may actually lowerthe body’s levels of vitamin D3—the form naturally produced by sunlight and more efficiently used by the body.

"Vitamin D supplements are important, especially between October and March," says Emily Brown, lead researcher from the University of Surrey. “But we found that vitamin D2 can decrease levels of D3, which was previously unknown. For most individuals, D3 may be the better choice.”

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D3,  the real immune hero: 

Backed by additional research from Frontiers in Immunology, vitamin D3 is shown to stimulate the type I interferon system—a key part of the immune response that kicks in when viruses or bacteria invade.

Professor Colin Smith, co-author of the study, explains: “Vitamin D3, but not D2, activates this crucial defence system. A healthy D3 status could help prevent infections from gaining a foothold.”

In essence, taking D2 could not only be less effective—it might be working against your natural immunity.

8 things to know before choosing your vitamin D supplement

• Vitamin D3 is more bioavailable: Your body uses it more efficiently

• D3 mirrors natural sunlight: It’s the form your skin produces when exposed to UVB

• D2 may lower D3 levels: Confirmed by new meta-analysis findings

• D3 boosts immune function: Proven to activate first-line virus defences

• Plant-based D3 is now available: Suited for vegetarians and vegans

• D2 is often cheaper, but less effective: Think long-term health, not short-term savings

• Not all fortified foods use D3: Check food and supplement labels carefully

• Talk to your doctor: Before switching supplements, especially if on prescribed doses

Vitamin D deficiency is a major concern in the UK, particularly in winter, with large parts of the population not getting enough. This new evidence may shift how supplements and fortified foods are made moving forward.

Professor Martin Warren, Chief Scientific Officer at the Quadram Institute, concludes says, “Choosing the most effective form of vitamin D is key to the nation’s health. D3 should be the priority for both supplementation and food innovation.”

FAQs about vitamin D2 and D3:

What is the difference between vitamin D2 and D3?

Vitamin D3 is more bioavailable and mirrors natural sunlight, whereas vitamin D2 may lower D3 levels, making it less effective.

Why is vitamin D3 considered better for immune function?

Vitamin D3 has been proven to activate first-line virus defences by stimulating the type I interferon system in the immune response.

Can vegetarians and vegans get vitamin D3?

Yes, plant-based D3 is now available, making it suitable for vegetarians and vegans.

Should I switch my vitamin D supplement?

Consult your doctor before switching supplements, especially if you are on prescribed doses.

Disclaimer: This article, including health and fitness advice, only provides generic information. Don’t treat it as a substitute for qualified medical opinion. Always consult a specialist for a specific health diagnosis.