Vitamin D goes by many names – wonder vitamin, sunshine nutrient, miracle worker. What makes it unique is its ability to convert itself into calcitriol, a hormone that helps regulate calcium and phosphorus levels in the body. Vitamin D also has the ability to absorb calcium from calcium-rich foods and use it to strengthen bones in the body.1
The link between vitamin D levels and glucose metabolism has been an active area of research. Many studies now associate low levels of vitamin D in the body with increased insulin resistance and higher chances of diabetes. Vitamin D sufficiency in turn is thought to provide protection against type 2 diabetes.
So What’s The Connection?
Type 2 diabetes develops when our body stops making enough insulin or becomes resistant to it, resulting in an impaired glucose metabolism. Vitamin D is supposed to have a predominant role in producing insulin, reducing resistance to insulin, and controlling glucose levels. A deficiency in vitamin D, therefore, can induce insulin resistance and increase chances of type 2 diabetes.2
Another connection between diabetes and vitamin D is attributed to the role of calcium. Vitamin D regulates calcium, which in turn controls the release of insulin. If there are fluctuations in the levels of calcium in the body, there is less insulin regulation, leading to diabetes. Vitamin D therefore indirectly controls insulin by regulating calcium.3
According to Clemente-Postigo et al., people with low levels of vitamin D are more prone to type 2 diabetes, prediabetes, and metabolic syndrome than people with normal vitamin D levels, irrespective of their weight.4 Another study by Dutta et al. showed that in prediabetic individuals with vitamin deficiency, a combination of vitamin D and calcium supplements, diet, and exercise could lower the chances of type 2 diabetes.5 According to the researchers, the risk of diabetes dropped by 8% for every unit increase in vitamin D levels achieved through supplementation. Large-scale interventionist studies will help make this connection clearer.
Vitamin D has an impact on diabetics too. According to an observational study by Joergersen et al., type 1 diabetes participants with very low levels of vitamin D were more likely to die (of varied causes) than those with sufficient levels of vitamin D. No link was found between vitamin D levels and the development of diabetes-induced kidney or eye disease. The researchers noted the need for further investigations to assess whether vitamin D supplements would benefit people with diabetes.6
Vitamin D, Be My Sunshine
Very few natural foods contain vitamin D. Fatty fish (mackerel, tuna, salmon), fish liver, beef liver, cheese, and egg yolks are some sources. One natural and easily accessible source of vitamin D is sunlight. When bare skin is exposed to sunlight, it quickly synthesizes vitamin D in the body. Approximately 5–30 minutes of sun exposure between 10 am and 3 pm at least twice a week to the face, arms, legs, or back without sunscreen leads to sufficient vitamin D content in the body.7 The amount of vitamin D absorbed from the sun depends on the color of the skin, time of the day, and the amount of skin exposed.
In dietary supplements and fortified foods, vitamin D is available as ergocalciferol and cholecalciferol. Some natural supplements include mushrooms grown in UV light, canned tuna, and fortified milk, cereals, and orange juice. The Food and Nutrition Board recommends the following daily intake of vitamin D: infants, 400 UI/day; children, 600 UI/day; adults, 600 UI/day; and seniors, 800 UI/day.8
Don’t Go Overboard
Excess intake of vitamin D can be harmful, causing vitamin D toxicity. This happens when you take 40,000 UI/day of vitamin D supplements for a long time. Consuming large amounts of vitamin D leads to the production of a chemical called 25(OH)D by the liver. High levels of this chemical can in turn lead to an increase in calcium levels in the blood, resulting in hypercalcemia.9
|↑1||Vitamin D (Calcitriol), Colorado State Uiversity.|
|↑2||Akankasha Goyal, Michelle Carey, Roger Maginley, Sarah Reda, Meredith Hawkins, Preeti Kishore, “Vitamin D administration improves hepatic insulin sensitivity and adipose tissue inflammation in obese, insulin resistant humans.” Endocrinology Division, Department of Medicine, Montefiore Medical Center/ AECOM, Bronx, NY, United States.|
|↑3||Type II diabetes, The Vitamin Council.|
|↑4||Clemente-Postigo, Mercedes, Araceli Muñoz-Garach, Marta Serrano, Lourdes Garrido-Sánchez, M. Rosa Bernal-López, Diego Fernández-García, Inmaculada Moreno-Santos et al. “Serum 25-hydroxyvitamin D and adipose tissue vitamin D receptor gene expression: relationship with obesity and type 2 diabetes.” The Journal of Clinical Endocrinology & Metabolism 100, no. 4 (2015): E591-E595.|
|↑5||Dutta, Deep, Samim Ali Mondal, Subhadip Choudhuri, Indira Maisnam, Abu Hena Hasanoor Reza, Basudeb Bhattacharya, Subhankar Chowdhury, and Satinath Mukhopadhyay. “Vitamin-D supplementation in prediabetes reduced progression to type 2 diabetes and was associated with decreased insulin resistance and systemic inflammation: An open label randomized prospective study from Eastern India.” Diabetes research and clinical practice 103, no. 3 (2014): e18-e23.|
|↑6||Joergensen, Christel, Peter Hovind, Anne Schmedes, Hans-Henrik Parving, and Peter Rossing. “Vitamin D levels, microvascular complications, and mortality in type 1 diabetes.” Diabetes care 34, no. 5 (2011): 1081-1085.|
|↑7||Holick, M.F., 2002. Sunlight and vitamin D. Journal of General Internal Medicine, 17(9), pp.733-735.|
|↑8||How do I get the vitamin D my body needs? Vitamin D Council.|
|↑9||Am I getting too much vitamin D? Vitamin D Council.|