Vitamin D Deficiency and Diabetes
While vitamin D deficiency has long been linked with bone disorders such as rickets, a large number of research studies have found evidence that it may increase a person’s risk for autoimmune disorders, particularly type 1 diabetes. More recent studies have found that a lack of vitamin D may also increase the risk of type 2 diabetes. Conversely, having consistently adequate levels seems to offer protection from colon cancer, as well as infections. This may seem like a pretty broad effect but studies have uncovered some facts that may explain that.
According to the article “Role of Vitamin D in Insulin Resistance,” by C. Sung, et al (Journal of Biomedicine and Biotechnology, volume 2012, article ID 634195) vitamin D has been found to be involved in tempering both the adaptive immune and inflammatory responses. It is also involved in managing cell proliferation and differentiation. That translates to helping the body attack foreign invaders but keeping it from attacking its own tissues. Autoimmune disorders are caused by the immune cells attacking the body’s tissues. Many immune cells have vitamin D receptor so it isn’t surprising that immune cells damaged by a vitamin D deficiency would be more likely to do that.
It is a little more complicated how vitamin D deficiency may promote the development of type 2 diabetes. What we do know is that there are receptors for vitamin D on pancreatic cells and the vitamin protects the insulin-producing beta cells in the pancreas from harmful immune cell attacks. It also improves beta cell functioning.
Insulin receptors are found on skeletal muscles, fat cells and in the liver. When insulin fits in these receptors, it causes the cells to allow glucose to enter so that the cells can make energy. But those receptors don’t work very well in those with type 2 diabetes. It is significant that vitamin D improves insulin receptor functioning, or, as it is often called, insulin sensitivity. If the vitamin protects insulin producing cells in the pancreas and enhances the functioning of the insulin receptors, it isn’t surprising that it lowers the risk of type 2 diabetes.
Since vitamin D is a fat-soluble vitamin, it is difficult for the body to get rid of excess vitamin D. The recommended intake for adults up to age 71 is 600 IU/day, and for those 71 and older its 800 IU/day. The upper limit is 4,000 IU/day. In The Clinical Advisor for August 2017, a study of vitamin D intake noted that people are taking more of it (“High-dose vitamin D supplements and adverse events”). 3% in the study exceeded that amount. It is too soon to say what the harmful effects are from too much vitamin D, but there doesn’t seem to be any benefit from exceeding that upper limit. This information isn’t intended to replace consultation with your health care provider and their recommendations.