Can vitamin D supplementation improve blood glucose levels in diabetics?

This study examined whether vitamin D supplementation can improve vitamin D levels, liver function and blood glucose levels in type 1 and type 2 diabetics.

Type 1 diabetes (T1D) is an autoimmune disease, meaning that the immune system attacks the cells of the pancreas which produce insulin and patients therefore don’t produce insulin. In type 2 diabetes (T2D), patients tend to produce insulin but it fails to work in the body. Some T2D patients eventually require insulin injections if the pancreas can’t release more insulin.

Both T1D and T2D patients can develop a vitamin D deficiency; however vitamin D deficiency is more common in T2D patients. Vitamin D is thought to improve blood glucose levels by increasing the release of insulin from the pancreas. Obesity, which is common among T2D patients, is associated with liver dysfunction. This liver dysfunction is believed to result in a vitamin D deficiency. 

This study compared vitamin D levels, liver function and blood glucose levels in T1D and T2D patients. This study involved 131 children and adolescents (88 T1D patients and 43 T2D patients). All participants lived in the same geographical area and so had similar sun exposure.

All participants took vitamin D supplements for an average of 3 months (7000IU for 2 months or 400-4000IU for 4 months). The dose of vitamin D given was based on the patient’s age and weight. Vitamin D levels and liver function were measured after 3 months supplementation. The HbA1c (a measurement of average blood glucose levels over the past 3 months) was measured over a 9 month period from the beginning of the study. 

Both T2D and T1D patients had higher vitamin D levels after 3 months. T2D patients had a greater improvement in liver function and a lower HbA1c (8.7% to 7.7% after 3 months), whereas T1D patients did not (8.5%).

This study concluded that vitamin D supplementation is associated with higher vitamin D levels, improved liver function and a decrease in average blood glucose levels in type 2 diabetes. 

The compliance of vitamin D supplementation was not assessed. Vitamin D supplementation was only given for 3 months so it’s not known whether longer supplementation might improve blood glucose levels in T2D or T1D patients. 

Consult your physician regarding the benefits of vitamin D supplementation for T2D.