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Human and Clinical Nutrition
Abbreviations: TC, total cholesterol
It is now estimated that over 20 % of adults in many Western countries have the metabolic syndrome with numbers continuing to increase(1,2). The metabolic syndrome is classified as a combination of risk factors such as obesity, atherogenic dyslipidaemia, hypertension, glucose intolerance and insulin resistance, which significantly increases the risk of developing CVD and type 2 diabetes mellitus(3,4). Many studies, including the National Health and Nutrition Examination Survey (1999-2004), and the Coronary Artery Risk Development In Young Adults study have suggested that higher dairy consumption reduces the risk of obesity(5,6). It has been proposed that specific components of dairy, such as Ca, other minerals, casein or whey proteins(7), may have beneficial effects on metabolic risk factors.
Milk contains two major protein groups: caseins and whey proteins. Caseins account for almost 80 % and whey accounts for 20 % of total protein in bovine milk(8). Casein and whey are both heterogeneous groups of proteins containing all the common amino acids, and are especially rich in the essential ones. Whey proteins contain globular proteins that can be isolated from whey, a by-product of cheese manufactured from cows' milk(8).
A study by Bowen et al.(9) suggested that the whey and casein protein components of dairy appear to be more important for weight loss than Ca in overweight adults due to their high concentrations of branched-chain amino acids. However, there is little evidence of beneficial effects of casein beyond it being a good quality source of protein and having a possible hypotensive effect(10-12). In a separate article, we have shown that both whey and casein proteins consumed over 12 weeks significantly reduced diastolic and systolic blood pressure from baseline in overweight individuals; however, whey protein consumption also significantly reduced arterial stiffness(12). Some studies demonstrate that dairy whey proteins have a better effect on appetite control than other protein sources such as egg and casein(13-15). In addition,...