Vitamin D Supplements: Who Really Needs Them?

Millions of people take vitamin D supplements every day, but new research suggests many of them may not need to - and some could even be putting their health at risk.

Known as the sunshine vitamin because the body produces it through sun exposure, vitamin D has long been celebrated for building strong bones and boosting calcium absorption. In recent years, researchers have linked low vitamin D levels to conditions ranging from heart disease and cancer to dementia and mood disorders, fuelling a surge in supplement use.

However, the science tells a more complicated story. A major US trial involving more than 25,000 adults found that vitamin D supplements did not reduce rates of heart attack, stroke or cancer. Separate trials published in 2025 found no benefit for memory, thinking or dementia prevention either.

The evidence is not entirely discouraging. The same large trial found that people who developed cancer and had taken vitamin D supplements for at least two years were 25 per cent less likely to die from the disease. Five years of supplementation was also linked to a 22 per cent lower risk of autoimmune conditions such as rheumatoid arthritis.

Guidelines from the Endocrine Society now state that healthy adults under 75 have no need to take supplements. Recommended groups include children, adults aged 75 and over, pregnant women and those with high-risk prediabetes.

There are also safety concerns. Vitamin D accumulates in body tissue rather than being flushed out, and excessive intake can cause calcium to build up in the blood, potentially damaging arteries and increasing the risk of kidney stones. Older adults taking high doses have also shown a greater risk of falls.

Doctors advise that people most at risk of deficiency include older adults, those with darker skin, people living in northern regions, and those with certain gut or liver conditions.