8-3 |
Modulation of disease risk through individualized diets: Role of calcium and dairy |
M. B. ZEMEL, Dept. of Nutrition, Univ. of Tennessee, 1215 W. Cumberland Ave., Knoxville, TN 37996-1920 Dietary calcium plays a pivotal role in the regulation of both blood pressure and energy metabolism/obesity risk. Intracellular calcium ([Ca2+]i) is a fundamental factor linking these conditions, and modulation of [Ca2+]i in target tissues by calcium-regulatory hormones provides an opportunity to modulate disease risk with dietary calcium. The increase in calcitriol in response to suboptimal calcium diets increases vascular smooth muscle [Ca2+]i and thereby increases blood pressure, while suppression of calcitriol with dietary calcium normalizes [Ca2+]i and thereby reduces blood pressure. Further, food calcium sources are markedly more effective than supplementary sources in controlling blood pressure. [Ca2+]i is also a key regulator of adipocyte lipid metabolism, as increased [Ca2+]i stimulates lipogenic gene expression and activity and inhibits lipolysis, resulting in increased adipocyte lipid accumulation. Further, calcitriol stimulates adipocyte Ca2+ influx and thereby promotes adiposity, while dietary calcium-suppression of calcitriol reduces adiposity. In support of this concept, low calcium diets accelerate weight gain and fat accretion in obesity-prone transgenic mice, while high calcium diets markedly inhibit lipogenesis, accelerate lipolysis, and suppress fat accretion and weight gain in animals maintained at identical caloric intakes and markedly accelerate fat loss secondary to caloric restriction. These concepts are confirmed by epidemiological and clinical trial data, both of which confirm protection from obesity with high calcium intakes. As with hypertension, dairy sources of calcium exert a markedly greater “anti-obesity” effect. This is likely attributable to additional bioactive compounds in dairy which act synergistically with calcium to attenuate adiposity; these include angiotensin converting enzyme (ACE) inhibitory peptides which limit angiotensin II stimulation of lipogenesis. However, although the dairy ACE inhibitor does attenuate adiposity, enriching the diet with both calcium and a dairy ACE inhibitor is significantly less effective than intact milk, suggesting that multiple components of dairy interact synergistically to exert a maximal anti-obesity effect.
Session 8, Tailoring food choices to improve health: What role will the food industry play?
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