The metabolic syndrome is a conditions characterised by insulin resistance and abdominal weight gain, and can increase the risk of developing diabetes and cardiovascular disease. The abdominal obesity associated with metabolic syndrome results in increased oxidative stress and inflammation due to the suppression of adiponectin and increased expression of cytokines. This pro-inflammatory condition is thought to be the mechanism that links abdominal obesity to an increased risk of cardiovascular disease. Calcium has shown beneficial properties in preventing weight gain in clinical trails, although its anti-obesity effect is not understood. In addition, epidemiological studies show an inverse association between dairy intakes and obesity risk. There is therefore interest in the effects of high calcium and dairy diets in the treatment of obesity and metabolic syndrome. Results from clinical studies suggest that increased dairy intakes are beneficial to subjects with metabolic syndrome.
Researchers1 have investigated the effects of two different dairy intakes on physiological parameters of metabolic syndrome in 40 overweight individuals. Subjects were randomly assigned to receive a high dairy diet containing 1200mg/d calcium or a low dairy diet containing 600mg/d calcium for 12 weeks. The results showed that by day 7, the high dairy intake decreased malondialdehyde and oxidised low density lipoprotein (LDL) by 35 and 7%, respectively. These markers of oxidative stress showed further reductions at 12 weeks. Reductions at day 7 and further declines at week 12 were also seen for the inflammatory markers tumour necrosis factor-α (-35%), interleukin-6 (-21%) and monocyte chemoattractant protein 1 (-24%). There was also a 55% increase in the plasma levels of adiponectin at week 12. In contrast, there was no change in the markers of oxidative stress or inflammatory stress in the low dairy group.
Interestingly, there was a decrease in the waist circumference and trunk fat of the subjects assigned to the high calcium diets, although there was no change in overall bodyweight. This suggests that the reason for the improvement in oxidative stress and inflammation may have been a reduction in abdominal adiposity seen with increased calcium intake. The rapid reductions in oxidative stress and inflammation may however suggest that the calcium caused beneficial metabolic effects aside from its weight loss effects. It has been shown that calcitonin stimulates inflammatory cytokine production in adipocytes in mice and that increasing the calcium intake attenuates the production and circulation of calcitonin. In addition, milk proteins in the whey fraction of milk are known to have insuliotropic effects and milk is also a source of conjugated linoleic acid that is known to have weight loss effects.
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