An increase in dairy food intake produces significant and substantial suppression of the oxidative and inflammatory stress associated with overweight and obesity. This trial was registered at clinicaltrials.gov as NCT00686426.

Background: The effects of dairy on energy metabolism appear to be mediated, in part, by leucine and calcium which regulate both adipocyte and skeletal muscle energy metabolism. We recently demonstrated that leucine and calcitriol regulate fatty acid oxidation in skeletal muscle cells in vitro, with leucine promoting and calcitriol suppressing fatty acid oxidation. Moreover, leucine coordinately regulated adipocyte lipid metabolism to promote flux of lipid to skeletal muscle and regulate metabolic flexibility. We have now investigated the role of mitochondrial biogenesis in mediating these effects.

We have recently shown 1alpha,25-dihydroxycholecalciferol increased oxidative stress and inflammatory stress in vitro, whereas suppression of 1alpha,25-dihydroxycholecalciferol with dietary calcium (Ca) decreased oxidative and inflammatory stress in vivo. However, dairy products contains additional factors, such as angiotensin-converting enzyme inhibitors, which may further suppress oxidative and inflammatory stress. Accordingly, this study was designed to study the effects of the short-term (3 wk) basal suboptimal Ca (0.4%), high-Ca (1.2% from CaCO(3)), and high-dairy (1.2% Ca from milk) obesigenic diets on oxidative and inflammatory stress in adipocyte fatty acid-binding protein-agouti transgenic mice. Adipose tissue reactive oxygen species (ROS) production and NADPH oxidase mRNA and plasma malondialdehyde (MDA) were reduced by the high-Ca diet (P < 0.001) compared with the basal diet and ROS and MDA were further decreased by the high-dairy diet (P < 0.001). The high-Ca and -dairy diets also resulted in suppression of adipose tissue tumor necrosis factor alpha and interleukin (IL)-6 mRNA (P = 0.001) compared with the basal diet, whereas an inverse pattern was noted for adiponectin and IL-15 mRNA (P = 0.002). Consequently, we conducted a follow-up evaluation of adiponectin and C-reactive protein (CRP) in archival samples from 2 previous clinical trials conducted in obese men and women. Twenty-four weeks of feeding a high-dairy eucaloric diet and hypocaloric diet resulted in an 11 (P < 0.03) and 29% (P < 0.01) decrease in CRP, respectively (post-test vs. pre-test), whereas there was no significant change in the low-dairy groups. Adiponectin decreased by 8% in subjects fed the eucaloric high-dairy diet (P = 0.003) and 18% in those fed the hypocaloric high-dairy diet (P < 0.05). These data demonstrate that dietary Ca suppresses adipose tissue oxidative and inflammatory stress.

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