The traditional view is that calcium is required for muscle contraction and skeletal health, but beyond these functions is generally not of concern to mainstream medicine. Further, the growing scientific evidence showing an inverse association between calcium intake and adiposity has been greeted in the mainstream by a resounding silence. The mainstream medical solution to weight gain is simply to instruct individuals to exercise more and eat less. This is despite a large body of research suggesting that neither calorie restriction nor exercise are effective long term solutions to obesity. Obesity may in fact be characterised by multiple mineral deficiencies that causes metabolic abnormalities and subsequent physiological changes. Data from animal studies, epidemiology and human clinical trials now suggests that dietary calcium is able to prevent weight gain through known and identified cellular mechanisms. Calcium deficiency should therefore be considered a risk factor for weight gain and obesity.
Nutritional researchers have been aware of the link between calcium and obesity for at least a decade, and the subject is well studied. For example, researchers1 investigated the relationship between calcium intake and body composition in 49 post-menopausal women. A 3-day diet record was used to estimate calcium intake and medical records and questionnaires were used to assess anthropometric measurements. Lean mass and fat mass were then measured with dual energy x-ray absorptiometry (DXA) total body scans. The mean body mass index of the women was 26.9kg/m2 and the mean percentage body fat was 42.8. The calcium intake for the subjects was estimated to be 1151mg/d. Calcium intake was significantly inversely associated with percentage body fat and abdominal fat mass, and lower calcium intakes were predictive of higher total body fat. However, there was no association between calcium and body mass index.
The results from this study support the theory that low calcium intakes cause insulin resistance, which in turn increases the risk of developing metabolic syndrome and obesity. Insulin resistance is a known risk factor for abdominal obesity and the relationship between calcium and abdominal obesity suggests that dietary calcium plays a role in maintaining insulin sensitivity. Low calcium intakes are known to cause plasma levels of calcium to fall. Metabolically, a plasma calcium deficiency may cause an increase in cellular levels of calcium through the action of 1,25-dihydroxyvitamin D in a process called the calcium paradox. The paradox exists because despite a low calcium intake, cellular levels of calcium increase. Increased cellular calcium interferes with the insulin receptor cascade, and results in insulin resistance. High calcium diets can reverse this process by suppressing plasma levels of 1,25-dihydroxyvitamin D and increasing insulin sensitivity.
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