The Vitamin D Debate: Conundrums and Complexities

Recent Studies Investigating Vitamin D Supplementation for Nonskeletal Indications

Despite the cautionary approach of the USPSTF, research into vitamin D suggests noteworthy associations between vitamin D deficiency and risk of nonskeletal conditions, including CVD, stroke, obesity, cancer, asthma, preterm births, and all-cause mortality.

• Researchers analyzed data of 2,148 subjects from the Cardiovascular Risk in Young Finns Study. The 25-hydroxyvitamin D [25-(OH)D] levels of subjects aged 3–18 years at baseline (in 1980) were measured from stored serum in 2010. Subjects were examined at age 30–45 years (in 2007). The main outcome measure was the carotid intima-media thickness (IMT), which is a surrogate measure of atherosclerosis. The researchers found that low 25-(OH)D levels in childhood were associated with increased carotid IMT in adulthood. They concluded that low 25-(OH)D levels in childhood “might have deleterious effects on vasculature.”⁵
• Stroke patients with low vitamin D levels were found to be more likely than those with normal vitamin D levels to suffer severe strokes and have poor health outcomes following the stroke. Henninger et al analyzed data from 96 stroke patients over a one-year period and found that patients who had low vitamin D levels (defined as <30ng/mL) had twice the areas of dead tissue resulting from obstruction of blood supply, as compared to patients with normal vitamin D levels. For each 10ng/mL reduction in vitamin D level, the chance for healthy recovery in the three months following the stroke decreased by almost half, regardless of the patient’s age or initial stroke severity.⁶
• Vitamin D deficiency has been associated with obesity and diabetes but the relationship is not clearly understood. Clemente-Postigo et al found that 25-(OH)D were diminished in prediabetic and diabetic patients, compared to normoglycemic subjects, independently of BMI and were closely related to glucose metabolism variables. They suggested that “vitamin D deficiency is associated more with carbohydrate metabolism than with obesity.”⁷