A food expert has shared a common supplement that could help lower the risk of a serious health condition. According to Professor Tim Spector, taking this pill regularly could reduce your chances of developing type 2 diabetes.

However, he acknowledged that we still don’t “fully understand” the effects of this supplement, and some studies suggest it might not be as beneficial as others claim.

In an episode of the Zoe Science and Nutrition podcast, Prof Spector discussed the potential health benefits of taking vitamin D. Prof Spector, an epidemiologist and founder of Zoe, explained how scientific findings on the effects of vitamin D have evolved over the years.

This included the use of vitamin D for osteoporosis - a health condition that weakens bones, making them fragile and more likely to break. He said: “I was a big promoter of vitamin D back in the day for osteoporosis.

“The early studies of vitamin D showed that it worked. And everybody worried about osteoporosis, trying to prevent it, should be on vitamin D medication. But when it actually got to the big studies with fractures, there was no difference.

“And that's now why osteoporosis experts know that vitamin D is not useful for the vast majority of people in preventing fractures.” The Royal Osteoporosis Society states on its website that vitamin D helps your body absorb and use calcium, which keeps your bones and muscles “strong”.

Further to this, the National Osteoporosis Guideline Group (NOGG) says that calcium and vitamin D contribute to bone health. But it acknowledges there is “little” evidence that vitamin D supplementation alone reduces fracture incidence, although it “may reduce falls risk”.

Prof Spector continued: “It's been promoted for a hundred different diseases, and I would say in 98 of them, it's complete rubbish. It’s probably useful if you’re at risk of multiple sclerosis, reduces by a few hours if you take it during a viral infection.”

Prof Spector then went on to summarise the link between vitamin D and diabetes. He said: “But the latest studies show that it can reduce your risk of getting type 2 diabetes.

“So it's a really interesting compound, which we still don't understand.” One meta-analysis of studies published in Diabetes Care journal in 2020 found that in people with pre-diabetes, taking vitamin D could lower the risk of type 2 diabetes.

As part of the research, the team identified eight eligible trials with a total of 4,896 subjects. They found that vitamin D supplementation “significantly reduced” the risk of type 2 diabetes (T2DM).

This benefit was found in non-obese participants but not in obese participants. The reversion of prediabetes to healthy blood sugar levels (normoglycaemia) occurred in 116 of 548 (21.2 per cent) participants in the vitamin D group and 75 of 532 (14.1 per cent) in the control group.

Study authors wrote: “Results from this meta-analysis show that vitamin D supplementation reduces the risk of T2DM in participants with prediabetes. Reversion of prediabetes to normoglycaemia was significantly increased by vitamin D supplementation.

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“The benefit of the prevention of T2DM appears to be confined to non-obese subjects. Individual participant data meta-analyses are needed to confirm the overall result and identify subgroups that benefit the most from supplementation.”

A separate study, published in the International Journal of Molecular Sciences in 2025, concluded: “Moreover, vitamin D has been reported to reduce the likelihood of developing diabetes by 15 per cent, particularly in doses higher than the traditional recommendations for bone health. Despite promising evidence, discrepancies in study designs, serum vitamin D measurements, and population-specific factors highlight the need for standardised methodologies and personalised approaches.

“In conclusion, vitamin D has complementary therapeutic potential in treating type 2 diabetes, revealing gaps in research, such as optimal dosing and long-term effects across populations.” But a separate review of studies, published in Cureus in 2022, found that “most studies” on the subject showed “no significant improvement” in blood sugar levels in type 2 diabetes patients.

Study authors wrote: “Most studies conducted to discuss the effects of vitamin D on glucose metabolism supported the hypothesis that appropriate vitamin D supplementation may improve the metabolic regulation of glucose levels in type 1 diabetes; in contrast, most of the studies showed no significant improvement in the levels of hemoglobin A1C in type 2 diabetes with supplementation of vitamin D. As the prevalence of diabetes rises and vitamin D insufficiency is quite common, more investigations and research are required to figure out the exact link between vitamin D and diabetes.”

The NHS states that vitamin D is needed to keep bones, teeth and muscles healthy. It says: “A lack of vitamin D can lead to bone deformities such as rickets in children, and bone pain caused by a condition called osteomalacia in adults.”

Most of the vitamin D we get is through sunlight. Therefore, the Government advice is that everyone should consider taking a daily vitamin D supplement during the autumn and winter.

The NHS website does not mention a link between vitamin D supplements and diabetes risk. If you choose to take vitamin D supplements, 10 micrograms a day will be “enough” for most people.

The healthy body says: “Do not take more than 100 micrograms (4,000 IU) of vitamin D a day as it could be harmful.” This applies to adults, including pregnant and breastfeeding women and the elderly, and children aged 11 to 17 years.

Children aged one to 10 years should not have more than 50 micrograms (2,000 IU) a day. Infants under 12 months should not have more than 25 micrograms (1,000 IU) a day.