Authors: Reinhold Vieth, Heike Bischoff-Ferrari, Barbara J Boucher, Bess Dawson-Hughes, Cedric F Garland, Robert P Heaney, Michael F Holick, Bruce W Hollis, Christel Lamberg-Allardt, John J McGrath, Anthony W Norman, Robert Scragg, Susan J Whiting, Walter C Willett and Armin Zittermann
The report by Hyppönen and Power in this issue of the Journal (1) highlights a frustrating and regrettable situation for nutrition researchers. In the early 1970s, the same serum 25-hydroxyvitamin D [25(OH)D] concentrations reported by Hyppönen and Power were thought to be indicative of “healthy” white adults in the United Kingdom (2). However, during those early years after the discovery of 25(OH)D, the adequacy of its serum concentration was based simply on whether the concentration was enough to prevent osteomalacia or rickets. Three decades later, we know that 25(OH)D concentrations relate to many other aspects of health, including fracture risk, bone density, colon cancer, and even tooth attachment (3); we also know that much higher concentrations of 25(OH)D are needed to prevent adverse outcomes. Indeed, in the 1958 British birth cohort, lower 25(OH)D is associated with a higher percentage of hemoglobin A1C (a measure of long-term glucose concentration), which further emphasizes the need to maintain optimal 25(OH)D concentrations.
Human diets do not provide sufficient vitamin D; if they did, the abovementioned associations between health and serum 25(OH)D concentrations would not be so routinely observed. The vitamin D provided by foods and supplements is overwhelmed by the effect of skin exposure to ultraviolet B light. Geography, season, skin color, and sun-related behavior are the main predictors of vitamin D nutritional status (6-10). Correction of low 25(OH)D concentrations can happen only if some or all of the following are implemented: the encouragement of safe, moderate exposure of skin to ultraviolet light; appropriate increases in food fortification with vitamin D; and the provision of higher doses of vitamin D in supplements for adults.
Evaluation of most relations of health and disease that involve vitamin D leads to the conclusion that a desirable 25(OH)D concentration is ≥75 nmol/L (30 ng/mL) (3-5). If a concentration of 75 nmol/L is the goal to be achieved by consumption of vitamin D, then why is it so rare for members of the population to accomplish this? One reason is that almost every time the public media report that vitamin D nutrition status is too low, or that higher vitamin D intakes may improve measures of health, the advice that accompanies the report is outdated and thus misleading. Media reports to the public are typically accompanied by a paragraph that approximates the following: “Current recommendations from the Institute of Medicine call for 200 IU/d from birth through age 50 y, 400 IU for those aged 51–70 y, and 600 IU for those aged >70 y. Some experts say that optimal amounts are closer to 1000 IU daily. Until more is known, it is wise not to overdo it.” The only conclusion that the public can draw from this is to do nothing different from what they have done in the past.
Supplemental intake of 400 IU vitamin D/d has only a modest effect on blood concentrations of 25(OH)D, raising them by 7–12 nmol/L, depending on the starting point. To raise 25(OH)D from 50 to 80 nmol/L requires an additional intake of {approx}1700 IU vitamin D/d (11). Safety is the first priority when giving advice to increase supplementation or fortification with any nutrient. A recent review in this Journal applied the risk assessment method used by the Food and Nutrition Board to update the safe tolerable upper intake level (UL) for vitamin D (12). The method focuses on the risk of hypercalcemia. The conclusion was that the UL for vitamin D consumption by adults should be 10 000 IU/d (12). This indicates that the margin of safety for vitamin D consumption for adults is >10 times any current recommended intakes.
The balance of the evidence leads to the conclusion that the public health is best served by a recommendation of higher daily intakes of vitamin D.
Emphasis mine. Originally published June 2007. http://www.ajcn.org/cgi/content/full/85/3/649
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