Ingrid Dean, PharmD Candidate
Earlier studies reported no such correlation between vitamin D and its negative influence on fasting glucose, improved insulin secretion, or reduction in hemoglobin A1c. However, these studies were limited by small sample sizes, non-diverse sample populations, and normal baseline vitamin D levels. On the other hand, most recent studies have compared the usage of insulin alone versus insulin and vitamin D combination therapy. Patients who received the combination therapy displayed long-term maintenance of beta cell function in contrast to those subjects treated with monotherapy.
For the most part, vitamin D is obtained through dietary intake but can be produced in the skin under ultraviolent radiation. Once obtained through dietary intake it is converted to its active metabolite calcitriol. Vitamin D is thought to enhance insulin production in the pancreas, improve insulin sensitivity, and improve long-term maintenance of beta cell function.
Researchers are also looking into vitamin D’s role in the treatment of metabolic syndrome (also known as syndrome X). Metabolic syndrome is a combination of several cardiovascular risk factors in a single patient which includes; insulin resistance, hypertension, and hypercholesterolemia. It is thought that as vitamin D increases insulin secretion and reduces insulin resistance, beta cells will then transport glucose into the cell resulting in lower blood glucose levels.
Cardiovascular disease, cerebrovascular disease, retinopathy, nephropathy, and neuropathy are complications associated with diabetes mellitus. Researchers suggested that insufficient amounts of vitamin D may be a contributing factor for the development of hypertension in diabetic patients. Zitterman and associates treated patients with calcitriol. The findings indicated that calcitriol decreases rennin activity and angiotensin levels; thereby, reducing patients’ risk of developing complications associated with diabetes mellitus.
Due to small sample sizes and normal baseline vitamin D levels, further research must be conducted to determine vitamin D potential benefit in patients suffering from diabetes mellitus. Also, further studies must include how sufficient if any reduction in hemoglobin A1c and fasting blood glucose levels is seen in patients. If it is determined to greatly alter hemoglobin A1c and blood glucose levels, vitamin D therapy could be considered adjunct therapy to insulin.
Alfonso B, Liao E, Busta A, et al. Vitamin D in Diabetes Mellitus – A New Field of Knowledge poised for D-velopment. Diabetes Metabolism Research and Reviews. 2009; 25:417-419.
Penckofer S, Kouba J, Wallis DE, et al. Vitamin D and Diabetes: Let The Sunshine In. The Diabetes Educator. 2008; 34:939-954.
Zitterman A. Vitamin D and Disease Prevention with Special Reference to Cardiovascular Disease. Prog Biophys Mol Biol. 2006; 92:39-48.