Vitamin D and Blood Glucose Management
As summer approaches in the Northern Hemisphere, we look forward to spending more time outdoors. This is good because our skin can synthesize vitamin D when exposed to sunlight. With most people spending most of their days indoors, serum 25(OH)D concentrations are known to decrease through the fall and winter months. The most recent data (NHANES 2007-2014) finds 24% of Americans have insufficient vitamin D levels (<50 nmol/L).
Historically, vitamin D requirements were construed to prevent rickets. Then in 2010, dietary recommendations were revised based on new data linking serum 25(OH)D3 concentrations associated with maintain bone health. However, emerging evidence suggests low vitamin D status may affect blood pressure, immune function, cardiovascular health and blood glucose control.
Glycosylated hemoglobin (HbA1c) is a measure of blood glucose control over the past 2-3 months. When blood glucose concentrations are elevated, glucose binds (glycosylates) hemoglobin to make HbA1c. For people without diabetes, HbA1c normally ranges between 5.7-6.4%. Levels above 6.5% are found in individuals with diabetes.
Sawah and colleagues recruited 197 children and adolescents (7-18y) with type 1 diabetes from a diabetes center in Philadelphia, PA. There found a high prevalence of vitamin D insufficiency with 41% of participants having serum 25-hydroxyvitamin D concentrations below 50 nmol/L. Only 10% were > 75 nmol/L. Mean HbA1c was 8.6%. As reported by Petitti and colleagues, low serum 25(OH)D3 concentrations were associated with higher glycosylated hemoglobin (HbA1c).
According to the American Diabetes Association, ~1.25 million American children and adults have type 1 diabetes. Type 2 diabetes is the more common form. In the US, diagnosed diabetes costs for 2012 are estimated at $245 billion. After adjusting for population age and sex differences, average medical expenditures among people with diagnosed diabetes were 2.3 times higher than what expenditures would be in the absence of diabetes.
Managing blood glucose levels is an important goal for individuals with diabetes. Maintaining sufficient vitamin D status (>50 nmol/L) is an important goal for everyone.
Sawah SA, Compher CW, Hanlon AL, Lipman TH. 25-hydroxyvitamin D and glycemic control: A cross-sectional study of children and adolescents with type 1 diabetes. 2016 Diab Res Clin Pract doi: 10.1016/j.diabres.2016.03.002
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Blondon M, Cushman M, Jenny N, Michos ED, Smith ML, Kestenbaum B, de Boer IH. Associations of serum 25-hydroxyvitamin D with hemostatic and inflammatory biomarkers in the Multi-Ethnic Study of Atherosclerosis. 2016 JCEM doi: 10. 1210/jc.2016-1368
Petitti DB, Klingensmith GJ, Bell RA, Andrews JS, Dabelea D, Imperatore G, Marcovina S, Pihoker C, Standifore D, Waitzfelder B, Mayer-Davis E. Glycemic control in youth with diabetes: The SEARCH for Diabetes in Youth Study. 2008. J Pediatr doi: 10.1016/j.jpeds.2009.05.025