CORRESPONDENCE: LETTER TO THE EDITOR
Vitamin D, Outdoor Happiness, and the Meaning of Deficiency
Dariush Mozaffarian, MD, DrPH*
* Division of Cardiovascular Medicine and Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Departments of Epidemiology and Nutrition, Harvard School of Public Health, 665 Huntington Avenue, Building 2-319, Boston, Massachusetts 02115 (Email: dmozaffa{at}hsph.harvard.edu).
Lee et al. (1) informatively review the emerging evidence for vitamin D as a lifestyle risk factor for cardiovascular disease. Two overlooked points should be highlighted. First, as the investigators note, the great majority of vitamin D is derived from sun exposure, rather than dietary consumption. Thus, effect estimates in studies of vitamin D levels and cardiovascular risk may be confounded, at least in part, by challenging-to-measure differences in lifestyles, behaviors, dispositions, and opportunities that lead individuals to enjoy and spend time in the sun, such as physical and social activities. Whereas vitamin D itself may still provide benefit, being outside and enjoying these activities are likely to provide additional health benefits that erroneously may be attributed as effects of vitamin D.
Second, vitamin D deficiency has become popularly (and variably) defined by suppression of counter-regulatory hormone levels or by risk of chronic disease, resulting in remarkably high proportions or even majorities of healthy populations being defined as deficient (2,3). Even if vitamin D is convincingly determined to prevent cardiovascular disease or cancer, as may be quite plausible, the departure of such metrics from more typical definitions of deficiency (4) based on prevention of overt deficiency symptoms or comparable biologic indicators must be explicitly recognized. Such novel definitions of deficiency could be arguably justified to reduce risk of chronic disease in the population because policy makers, health providers, and the public each seem to respond much more urgently to concerns over individuals having deficient versus suboptimal exposures. Based on this same logic, however, the strength, consistency, and breadth of scientific evidence would argue for highlighting more strongly the current worldwide pandemics of omega-3 deficiency, whole-grain deficiency, vegetable deficiency, and physical activity deficiency, among others. For example, long-chain omega-3 fatty acids have robust associations with lower risk of coronary heart disease death in numerous well-performed observational studies, including 16 prospective cohort studies of 326,572 generally healthy individuals from the U.S., Europe, and Asia; significant cardiovascular benefits in 4 of 5 large randomized controlled trials of dietary or supplement omega-3s in 36,431 patients with and without established heart disease; and 10-fold differences in risk of sudden cardiac death with modest differences in circulating blood levels (5). At a time when the Institute of Medicine is being urged to revise dietary requirements for vitamin D based on novel definitions of deficiency, these considerations and comparisons cannot be overlooked.
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Footnotes
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Please note: Dr. Mozaffarian has received research grants (significant) from the National Heart, Lung, and Blood Institute and National Institute of Environment Health Sciences (K08 HL 075628-01, R01 HL 085710-01, R01 ES 014433-01A2); the Searle Scholar Award from the Searle Funds at the Chicago Community Trust; the Genes and Environment Initiative at the Harvard School of Public Health; the Gates Foundation/World Health Organization Global Burden of Diseases, Injuries, and Risk Factors Study; and GlaxoSmithKline, Sigma Tau, and Pronova for an investigator-initiated trial of fish oil to prevent post-surgical arrhythmia. He has also received small royalty payments (<$1,000/year) for a chapter on fish oil in UpToDate and honoraria (modest) from scientific associations and universities for speaking at scientific conferences and reviewing on topics related to diet and cardiovascular disease, including from the U.S. Food and Drug Administration, Food and Agriculture Organization of the United Nations, World Health Organization, American Diabetes Association, American Dietetic Association, American Oil Chemists Society, National Lipid Association, Institute of Food Technologists, International Life Sciences Institute, Aramark, Medical Society of Delaware, Johns Hopkins University, Columbia University, University of New Hampshire, University of Guelph, and Washington University.
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References
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1. Lee JH, O'Keefe JH, Bell D, Hensrud DD, Holick MF. Vitamin D deficiency an important, common, and easily treatable cardiovascular risk factor? J Am Coll Cardiol 2008;52:1949-1956.[Abstract/Free Full Text]2. Looker AC, Dawson-Hughes B, Calvo MS, Gunter EW, Sahyoun NR. Serum 25-hydroxyvitamin D status of adolescents and adults in two seasonal subpopulations from NHANES III Bone 2002;30:771-777.[CrossRef][Web of Science][Medline] 3. Rovner AJ, O'Brien KO. Hypovitaminosis D among healthy children in the United States: a review of the current evidence Arch Pediatr Adolesc Med 2008;162:513-519.[Abstract/Free Full Text] 4. Institute of Medicine Dietary Reference Intakes: The Essential Guide to Nutrient RequirementsWashington, DC: National Academies Press; 2006. 5. Mozaffarian D, Rimm EB. Fish intake, contaminants, and human health: evaluating the risks and the benefits JAMA 2006;296:1885-1899.[Abstract/Free Full Text]
Related Article
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- James H. O'Keefe, John H. Lee, David S.H. Bell, and Michael F. Holick
J. Am. Coll. Cardiol. 2009 53: 2012-2013.
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