Professor Tim Spector has shared that these supplements may help lower the risk of developing type 2 diabetes
A nutrition expert has revealed a widely-available supplement that may help reduce the likelihood of a severe health condition. According to Professor Tim Spector, regularly taking this tablet could lower your risk of developing type 2 diabetes.
However, he admitted that we still don’t “fully understand” how this supplement works. And certain research indicates it might not be as advantageous as some claim.
During an episode of the Zoe Science and Nutrition podcast, Prof Spector explored the possible health advantages of taking vitamin D. Prof Spector, an epidemiologist and Zoe’s founder, detailed how scientific evidence regarding vitamin D’s effects has changed through the years.
This included vitamin D’s use for osteoporosis – a condition that weakens bones, leaving them fragile and at greater risk of breaking. 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 confirms on its website that vitamin D assists your body in absorbing and utilising calcium, which maintains your bones and muscles “strong”.
Additionally, the National Osteoporosis Guideline Group (NOGG) states that calcium and vitamin D support bone health. However, it recognises there is “little” evidence that vitamin D supplementation by itself decreases fracture occurrence, though it “may reduce falls risk”.
Prof Spector added: “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.”
Vitamin D and diabetes
Prof Spector then summarised the connection 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.” A meta-analysis of research published in Diabetes Care journal in 2020 discovered that among people with pre-diabetes, consuming vitamin D could decrease the likelihood of developing type 2 diabetes.
During the research, the team identified eight suitable trials involving a total of 4,896 participants. They discovered that vitamin D supplementation “significantly reduced” the risk of type 2 diabetes (T2DM).
This advantage was observed in non-obese participants but not amongst obese participants. The reversal of prediabetes to normal blood sugar levels (normoglycaemia) was seen 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. The study’s authors stated: “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.
“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.”
Another study, published in the International Journal of Molecular Sciences in 2025, found: “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.” However, a different review of studies, published in Cureus in 2022, discovered that “most studies” examining this topic demonstrated “no significant improvement” in blood sugar levels amongst type 2 diabetes patients.
The study’s authors stated: “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.”
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NHS guidance
The NHS explains that vitamin D is essential for maintaining healthy bones, teeth and muscles. It warns: “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.”
The majority of our vitamin D comes from exposure to sunlight. Consequently, Government guidance recommends that everyone should consider taking a daily vitamin D supplement throughout the autumn and winter months.
The NHS website makes no reference to any connection between vitamin D supplements and diabetes risk. Should you decide to take vitamin D supplements, 10 micrograms daily will be “enough” for the majority of people.
The health body advises: “Do not take more than 100 micrograms (4,000 IU) of vitamin D a day as it could be harmful.” This guidance applies to adults, including expectant and nursing mothers and elderly people, as well as children aged 11 to 17 years. Youngsters between one and 10 years old shouldn’t exceed 50 micrograms (2,000 IU) daily. Babies under 12 months shouldn’t have more than 25 micrograms (1,000 IU) per day.
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