New Delhi, Jan. 9: Doctors in Calcutta have suggested that vitamin D therapy can reduce the risk of onset of diabetes among people who are already susceptible to developing the disease in the first such study in India.
The doctors at the Institute of Postgraduate Medical Education and Research (IPGMER) and SSKM Hospital have shown that vitamin D can delay diabetes in sections of patients who have impaired glucose tolerance.
Endocrinologists have described the study’s findings as significant because vitamin D deficiency and impaired glucose tolerance — a precursor to diabetes in which the body cannot efficiently mop up blood sugar despite normal insulin levels — are believed to be widely prevalent across India. The findings are published this week in the international journal Diabetes Research and Clinical Practice.
“We’ve found vitamin D offers a clear benefit to people with high levels of fasting glucose or post-meal glucose but do not have diabetes yet,” said Satinath Mukhopadhyay, professor of endocrinology at the IPGMER.
The other IPGMER-SSKM team members are Deep Dutta, Samim Ali Mondal, Subhadip Choudhuri, Indira Maisnam, Abu Hena Hasanoor Reza, Basudeb Bhattacharya and Subhankar Chowdhury.
While several earlier studies have shown that vitamin D deficiency increases the risk of diabetes, doctors say there is no conclusive evidence thus far on the effectiveness of vitamin D to prevent the onset of diabetes among people already at risk.
Over the past decade, medical studies from across the country have indicated a widespread prevalence of vitamin D deficiency — ranging from 50 per cent to 80 per cent — among healthy people.
While vitamin D is available from certain fatty fish such as mackerel and, in tiny amounts, from egg yolk, its primary source is sunshine — the body synthesises this vitamin when the skin is exposed to sunlight.
Mukhopadhyay and his colleagues selected 115 patients who had been diagnosed with impaired glucose tolerance and randomised them into two groups — those in one group received vitamin D and calcium, while those in the second received only calcium.
The doctors also prescribed patients in both groups lifestyle changes such as diet and exercise and followed them up for more than two years during the duration of the study from 2009 through 2013.
The proportion of patients with impaired glucose status who developed diabetes was lower and the proportion who reverted to normal glucose levels was higher among those who received vitamin D than among those who did not.
The patients were prescribed vitamin D once a week for eight weeks, then once a month during the rest of the study.
Their analysis has shown that every unit increase in the vitamin D levels in the body in those who had impaired glucose tolerance was associated with an 8 per cent decreased risk of progression to diabetes.
“Without diet and lifestyle changes, nothing works,” said Dutta, an endocrinologist and team member at the IPGMER and SSKM Hospital. Members of both groups lost some weight during the study period.
But the researchers saw no change in weight and documented anticipated levels of progression to diabetes among members of a third group of people who had impaired glucose tolerance but no vitamin D deficiency that were also followed up in the study.
Doctors caution that the findings are based on a small sample of patients and would need to be validated through larger studies. “The idea that vitamin D therapy can delay or prevent onset of diabetes has not been solidly established yet,” said Ambrish Mithal, the chairman of endocrinology and diabetes at Medanta hospital in New Delhi, who was not associated with the Calcutta study.
“It’s been widely shown that vitamin D deficiency increases the risk of diabetes, but an intervention study actually showing a delay in onset would be an interesting development,” Mithal told this newspaper.
Surveys in select Indian cities suggest that 8 per cent to 15 per cent of the adult population may suffer from impaired glucose tolerance. “About one-third of people in this pre-diabetes state spontaneously return to normal glucose levels — with vitamin D, we show the proportion that reverts is higher,” said Mukhopadhyay.
Medical researchers in the US, too, are investing in similar studies. The US National Institutes of Health last October approved $40-million grant to Tufts Medical Centre in Boston for a nationwide study to determine if vitamin D therapy can reduce the likelihood of developing diabetes among people at high risk.
“While there is a lot of hype about vitamin D and its health benefits, including for diabetes, there is not yet enough evidence from clinical trials to support (the use of) vitamin D for diabetes prevention,” Anastassios Pittas, an endocrinologist at Tufts said in a media release issued last October announcing the launch of the trial.
The US study will recruit 2,500 people from 17 states across the country. “We now need a similar large multi-centred study in India,” Mukhopadhyay said.