The study findings suggest that high-dose supplementation of vitamin D can improve glucose metabolism to help prevent the development and progression of diabetes.
“The reason we saw improvements in glucose metabolism following vitamin D supplementation is unclear”
The study authors noted that people at high risk of developing type 2 diabetes – also known as pre-diabetes – could be identified by several risk factors including obesity or a family history.
They said although low vitamin D levels had previously been associated with an increased risk of developing type 2 diabetes, some studies had reported no improvement in metabolic function.
But they said these often had a low number of participants or included people with normal vitamin D levels at the start who were metabolically healthy, or who had long-standing type 2 diabetes.
Whether supplements had any beneficial effect for patients with pre-diabetes or newly diagnosed diabetes, had previously remained uncertain, said the team from Université Laval in Quebec.
In their study, they examined the effect of vitamin D supplementation on glucose metabolism in patients newly diagnosed with type 2 diabetes or identified as at high risk of developing it.
They randomised 96 patients to receive either 5,000 IU daily of vitamin D supplementation or a placebo for six months.
Markers of insulin function and glucose metabolism were measured before and after six months of high-dose vitamin D supplementation.
Although only 46% of participants were determined to have low vitamin D levels at the start of the study, supplementation significantly improved the action of insulin in muscle tissue after six months.
“I would suggest that current vitamin D supplementation recommendations be followed”
Senior study author Dr Claudia Gagnon said: “The reason we saw improvements in glucose metabolism following vitamin D supplementation in those at high risk of diabetes, or with newly diagnosed diabetes, while other studies failed to demonstrate an effect in people with long-standing type 2 diabetes, is unclear.
“This could be due to the fact that improvements in metabolic function are harder to detect in those with longer-term disease or that a longer treatment time is needed to see the benefits.”
Dr Gagnon suggested future studies should evaluate whether there were individual clinical or genetic factors that affected how different people responded to vitamin D supplementation.
She added: “Type 2 diabetes and pre-diabetes are a growing public health concern and, although our results are promising, further studies are required to confirm our findings, to identify whether some people may benefit more from this intervention, and to evaluate the safety of high-dose vitamin D supplementation in the long term.
“Until then, I would suggest that current vitamin D supplementation recommendations be followed,” she said.
The new findings have been published this month in the European Journal of Endocrinology, the official clinical journal of the European Society of Endocrinology.