Milk products

 

From a mechanistic viewpoint, whey protein administered before a meal exerted insulinotropic effects and reduced postprandial insulinemic fluctuations in healthy participants (41) and in type 2 diabetic patients (42). Even though the available evidence is not conclusive, some studies suggest that milk and its derivatives might actually be beneficial to some population segments. These effects have been observed in healthy participants as well as in overweight, obese (21, 24–27), and diabetic (8, 28) patients. Studies have been performed on these compounds as either isolated molecules (3–9) or as components of milk and dairy products (5, 7, 8, 10–12). As an example, the effects of milk (notably skimmed milk) on body weight appear to be well documented, and the conclusions of the vast majority of published studies indicate that dairy consumption does not increase cardiovascular risk or the incidence of some cancers. In addition to casein, whey protein appears to be particularly effective (29, 30), and their actions seem to be mediated by several mechanisms that include increased satiety and decreased appetite (29). Even though mammals produce milk to feed their offspring, in many areas of the world humans continue to consume milk throughout their life. Although future studies will help elucidate the role of milk and dairy products in human health, their use within a balanced diet should be considered in the absence of clear contraindications.

Milk is an essential component of the diet of ~6 billion people. In particular, visceral adipose tissue was significantly affected (26). The world production of milk reaches 730 million tons/y (1, 2). Milk is recognized as being useful during childhood and adolescence because of its composition; however, its relatively high saturated fat proportion raises issues of potential detrimental effects, namely on the cardiovascular system. However, no beneficial effect of increasing dairy consumption on body weight and fat loss was seen in long-term studies or in studies without energy restriction, which calls for caution in attributing milk to slimming properties.

. In agreement with these studies, Dove et al. (44) reported that the intake of 600 mL of skimmed milk at breakfast (by 34 overweight men and women) had a stronger satiating effect (evaluated 4 h later) than that of an isocaloric intake of fruit juice. In particular, the fat portion of milk (largely composed of SFAs) and some of its minor components, notably calcium and oligosaccharides, are being actively researched for their potential health roles.

This review summarizes the most recent studies on milk and human health and critically discusses the putative actions of milk and principal dairy constituents.

Of all the bioactive milk components, calcium and vitamin D have been chiefly studied for their effects on body weight and adipose tissue. For example, in addition to calcium and vitamin D, dairy proteins are being suggested as reducers of adipose mass (namely, visceral fat) and body weight (11, 14, 22, 23). In particular, inhibition of gastric secretion by cholecystokinin (31) and some branched amino acids, the abundance of leucine (32), increased secretion of glucagon-like peptide 1 (GLP-1)4 (33, 34) and glucose- dependent insulinotropic polypeptide (GIP) (35), the concomitant suppression of ghrelin secretion (36), and the potent satiating effects of α-lactoalbumin (37) synergistically contribute to weight control.

The most recent studies in this area include randomized clinical trials and meta-analyses. This effect is quantitatively comparable to that of sulfonilureas (43). A marked reduction in adipose tissue and an increase in lean mass were observed in 90 overweight and obese premenopausal women after 4 mo of a hypocaloric diet that included milk and dairy products. Male participants also witnessed a protective effect on abdominal obesity. Proposed targets include thermogenesis and lipid oxidation (which are enhanced by calcium and vitamin D) (13–15) and increased lipid fecal excretion (16–19).

In the past few years, some studies have been published on other milk components and their potential effects on body weight (20, 21). In the latter, consumption of whey protein before a high-glycemic-load (white bread and potatoes) breakfast or lunch increased insulin response by 30–50% and reduced glycemia by ~20%, compared with controls (42). Milk is a widely consumed beverage that is essential to the diet of several millions of people worldwide because it provides important macro- and micronutrients. A study conducted in 903 healthy adolescents (15–16 y) that included at least 2 servings/d [1 serving = 200 mL of milk, 125 g of yogurt, or 28 g of cheese (38)] of dairy reported a significant weight loss and a reduction in body fat (39, 40). Therefore, the impact of milk and dairy products on human health is quantitatively relevant and has been the subject of several investigations, on both whole products and their isolated components. This review evaluates the most recent literature on dairy and human health, framed within epidemiologic, experimental, and biochemical evidence. However, it must be emphasized that lactose intolerance is widespread throughout the world and that a large proportion of the world's population would not benefit from the putative benefits of milk.

In addition to milk, several dairy products such as cream, butter, yogurt, kefir, and cheese have been produced and consumed worldwide for millennia. A significantly lower consumption of foods offered ad libitum at lunch (i.e., after 4 h) was also recorded (44).

A recent meta-analysis (45) that reviewed the effect of 29 randomized clinical trials comprising 2101 cases confirmed the weight-loss effect of milk and dairy products when incorporated into hypocaloric diets