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Rapid Responses to:
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Electronic letters published:
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Obesity, inflammation, mortality, and iron.
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Jerome L Sullivan, MD, PhD University of Florida College of Medicine, Luca Mascitelli, MD and Francesca Pezzetta, MD
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jlsullivan{at}pol.net Jerome L Sullivan, et al.
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Van Dam et al (1) found that higher adiposity at age 18 years is associated with increased premature death in women. Hazard ratios for death were adjusted for potential confounders, including smoking, alcohol use, and physical activity. They were unable to exclude residual confounding by “unknown confounders” (1). A potential confounder not addressed by the authors is iron storage level. Stored iron level may be associated with mortality from multiple causes including cardiovascular diseases, neoplasms and infectious diseases (2). Iron accumulation is also positively associated with adiposity (3). Complex interactions may be involved in the association of iron stores with BMI, however these likely include the simple mechanism of a net increase in iron absorption from increased exposure of gut mucosa to an absolute increase in iron associated with elevated food consumption. Storage iron is regarded as normal. Humans have a system to assure that unused iron is stored in the body under conditions of excess dietary iron. An evolved system is also in place to assure that excess food is stored as fat. Those with an uninterrupted super-sized abundance of food tend to become overweight with the passage of decades. Higher than optimal set points for stored iron and stored fat may have evolved to assure adequate supplies of both in times of deprivation. Both set points may be excessively high for conditions of continuous excesses of available food and highly absorbable iron. Iron and food intakes may each have two optima: high levels associated with maximal growth rates, but much lower levels to assure maximal longevity (2). Stored iron is an obesity-associated factor that can be manipulated more easily than other confounders such as smoking, alcohol use or physical activity. Long term maintenance of a state of iron depletion, e.g. by a series of phlebotomies, is more feasible than successful weight reduction. Iron stores can be controlled by non-dietary methods independently of BMI. Increased iron may in part explain the association of obesity with oxidative stress and inflammation (4). Removal of all storage iron or induction of a state of “near iron deficiency” (5) can be accomplished without reduction in BMI. It should thus be possible in a clinical trial to determine the contribution of increased stored iron to the effects of obesity on biomarkers of oxidative stress and inflammation. In a number of experimental systems, removal of stored iron is protective against oxidative or inflammatory injury (2). (1) van Dam RM, Willett WC, Manson JE, Hu FB. The Relationship between Overweight in Adolescence and Premature Death in Women. Ann Intern Med. 2006;145:91-97. (2) Sullivan J. Is stored iron safe? J Lab Clin Med. 2004;144:280- 284. (3) Liu JM, Hankinson SE, Stampfer MJ, Rifai N, Willett WC, Ma J. Body iron stores and their determinants in healthy postmenopausal US women. Am J Clin Nutr. 2003;78:1160-1167. (4) Vincent HK, Taylor AG. Biomarkers and potential mechanisms of obesity-induced oxidant stress in humans. Int J Obes. 2005;30:400-418. (5) Facchini FS, Saylor KL. Effect of iron depletion on cardiovascular risk factors: studies in carbohydrate-intolerant patients. Ann N Y Acad Sci. 2002;967:342-51. Conflict of Interest:None declared |
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