Vitamin D Deficiency: A Major Public Health Problem?

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Vitamin D Deficiency: A Major Public Health Problem?Hypovitaminosis D is epidemic, with possible clinical consequences.During the past decade, we've learned two remarkable things about vitamin D. First, many adults and children in the U.S. and other developed nations have vitamin D deficiency (JW Gen Med Mar

20 1998). Second, the adverse health effects of vitamin D deficiency could extend well beyond bone disease to encompass excess risk for cancer (particularly colon, prostate, and breast), hypertension, autoimmune diseases (e.g., multiple sclerosis, type 1 diabetes), and other diseases. Vitamin D deficiency also might be associated with all-cause and cardiovascular mortality. In the past year, several new studies have added to the evidence that hypovitaminosis D is epidemic, with possible clinical consequences.Data from 6275 children who were selected at random in the 2004 National Health and Nutrition Examination Survey (NHANES) showed vitamin D deficiency (serum 25-hydroxyvitamin D [25(OH)D] level <15 ng/mL) in 9% and insufficiency (15–29 ng/mL) in 61%, with considerably higher rates in non-Latino black teens. Data from NHANES also showed that 25(OH)D levels were related inversely to systolic blood pressure and plasma glucose in teens (JW Pediatr Adolesc Med Nov 4 2009).In another study, researchers found that half of 1300 randomly selected older adults (age range, 65–88) had 25(OH)D levels <20 ng/mL (JW Gen Med Apr 23 2009). The results of this study, and one other study of 1300 men older than 65 (JW Gen Med Aug 13 2009), showed adverse effects on bone metabolism (as reflected by bone-mineral

density, bone turnover markers, and serum parathyroid hormone levels) when 25(OH)D levels dropped lower than 20 ng/mL.In a population-based study, investigators compared vitamin D levels recorded in the NHANES database for 1988–1994 and for 2001–2004; they found that levels of 25(OH)D are decreasing. The prevalence of a serum level 30 ng/mL dropped from 45% to 23%, a trend that was present in both sexes, across all ethnic groups, and across all age groups (JW Gen Med Apr 21 2009).A meta-analysis of eight randomized trials that involved 2426 older patients showed that higher doses of daily vitamin D supplements (700–1000 IU) lowered risk for falling by 19%, presumably because of better muscle strength (JW Gen Med Nov 3 2009). Previous research had suggested that high-dose supplementation also prevents fractures (JW Gen Med Jun 3

2005).Major issues remain unresolved. A 25(OH)D level <20 ng/mL clearly is associated with adverse effects on bone. However, the protective effect of vitamin D on other diseases seems to be linear: Increasing levels are associated with a decreasing rate of morbidity (at least up to serum levels of around 70 ng/mL). So the definition of vitamin D "deficiency" remains unclear. Also unanswered is the question of whether doctors should obtain blood levels of 25(OH)D routinely and adjust supplemental doses

to achieve a target blood level — and what should that level be? A very large multi-year randomized trial has been designed to evaluate the possible effects of supplementation on many diseases; recruitment will begin in January 2010. Past observational studies that suggested other vitamin supplements might improve health often have not been confirmed by randomized trials.— L. Komaroff, MDPublished in Journal Watch General Medicine December 31, 2009 Regards, Vergelpowerusa dot org