While researchers have known that there is some link between Vitamin D deficiency and Type 2 diabetes, they still do not know whether or how one affects the other. A recently published review by US researchers looks at the factors that lead to differences in Vitamin D levels in the blood despite similar exposure to sun or supplementation. The study points out that absorption of vitamin D is higher when the exposure to sun is at a non-inflammatory level, obese individuals need more supplements as Vitamin D can get stored in the fat tissues, and that women usually have higher levels of vitamin D because oestrogen likely increases its levels in the blood. Dr Anoop Misra, Chairman of Fortis-CDOC Centre of Excellence for Diabetes, Metabolic Diseases and Endocrinology in New Delhi, and his team has also worked with Vitamin D deficiency and Type 2 diabetes. He says that although the connection between the two is not very well understood, Vitamin D supplementation can be given to people in prediabetic stages to slow progression to diabetes. Does Vitamin D have a role in the treatment of Type 2 diabetes? We still do not understand the connection between the two. However, the results of a number of cross-sectional studies in the Western population as well as the Indian population are quite convincing. They show that a link does exist. This is especially important because we have a very high prevalence of Vitamin D deficiency in the population, even in those who live in rural areas with a very high exposure to the sun. However, prospective studies from the West on whether Vitamin D supplementation in prediabetic patients helps have not been convincing. However, a similar study by our team has shown that Vitamin D supplementation can help in slowing the progression to Type 2 diabetes. The difference in results could be because of the difference in physiology. We have higher levels of Vitamin D deficiency, and we have a higher prevalence of Type 2 diabetes. Some think that Vitamin D perhaps increases the sensitivity of cells to insulin thereby preventing diabetes. So, along with the existing interventions like diet and exercise, Vitamin D supplements can also be given to prediabetics, provided they are taken in safe levels under medical supervision. What are safe levels for Vitamin D supplements? Vitamin D supplementation should not be overdone. If you test the levels of vitamin D in the blood and then supplement it accordingly, it is completely safe. However, it may not be safe to administer it in very high levels with multiple high dose injections. (Some studies claim that high doses of Vitamin D supplementation are needed to maintain its levels in the blood.) What are the determinants of Vitamin D absorption in a person? And, why despite our exposure to sunlight, the deficiency is high among Indians? Environmental factors like when the exposure happens, our skin colour, our metabolism and obesity play a role in our levels of Vitamin D. What we know so far is that the exposure should ideally happen between 11 am and 2 pm for around 20 minutes. We know that Vitamin D levels in the blood are lower for those who are obese. Skin colour is one of the biggest determinants of how much Vitamin D is produced despite similar exposures to the sun. The darker the skin, the less the levels of Vitamin D they have. More importantly, Vitamin D levels are low even among rural populations in India. Why the people who are out working in the fields should have low levels of Vitamin D is still a mystery. Most studies show that Vitamin D deficiency in India ranges from 70 per cent to 90 per cent of the population. A study by our team found the deficiency to be over 85 per cent even in rural areas. If 90 per cent of our population has low levels of Vitamin D, shouldn’t the low levels be normal for us? Who can say what “normal” levels of vitamin D are? All we can say is what are the 90th percentile levels, 70th percentile levels and so on. Vitamin D has an impact on several systems in the body. We all know its importance when it comes to bone health. It also strengthens immunity and has a big impact on infections, especially pulmonary infections and tuberculosis. It also has some impact on cardiovascular diseases. It is linked to almost all the systems but that’s not proven enough. There is a need for long-term prospective studies with focus on a disease to see the impact of Vitamin D levels and whether supplementation helps. So, at present who should be given supplements? Well, if a person has osteoporosis (a condition where bone density and mass decreases) and low levels of Vitamin D, they should be given supplements. If a person has very low Vitamin D levels, they should also be advised supplements. And, even for preventing progression of people from prediabetes to diabetes, Vitamin D supplements may be given. (Why Dr Misra? Dr Anoop Misra is the Chairman of Fortis-CDOC Centre of Excellence for Diabetes, Metabolic Diseases, and Endocrinology in New Delhi. His team has conducted several studies to check the levels of Vitamin D in the population and the associated levels of type-2 diabetes. He has been an advisor to the Ministry of Health, the Indian Council of Medical Research (ICMR), and the Department of Biotechnology, offering his expertise on several issues related to diabetes and other non-communicable diseases. In the past two years, Dr Misra has published 40 papers on Diabetes and Covid-19 in top science journals.)
