Controversies in Vitamin D Supplementation
Concurrent with the rise in vitamin D ingestion were the epidemic onsets of atherosclerosis and osteoporosis, which led to the hypothesis that vitamin D excess contributes to the development of these illnesses (1). A recent study found that vitamin D induced an increase in vascular smooth muscle cell migration in rat aorta, suggesting a possible mechanism of vitamin D in atherosclerosis (2). On the other hand, Rucker and colleagues found that 34% of the 188 healthy Canadians whom they tested were vitamin D insufficient in at least one occasion and recommended more aggressive vitamin D supplementation (3). Chapuy et al. reported that elderly women who took calcium and vitamin D supplements had reduced hip bone loss and risk of hip fracture (4). Although the research on vitamin D supplementation is still inconclusive, the potential association between high vitamin D ingestion and diseases such as atherosclerosis provides ample reason for caution. Since 15 minutes of exposure to sunlight three times a week is sufficient to produce the body's requirement of vitamin D, there is no need for healthy individuals to take vitamin D supplements (5). In addition, the current practice of rampant fortification of foods with vitamin D should be reevaluated.