Dairy Foods, Obesity, and Metabolic Health: The Role of the Food Matrix Compared with Single Nutrients

Abstract

In the 20th century, scientific and geopolitical events led to the concept of food as a delivery system for calories and specific isolated nutrients. As a result, conventional dietary guidelines have focused on individual nutrients to maintain health and prevent disease. For dairy foods, this has led to general dietary recommendations to consume 2-3 daily servings of reduced-fat dairy foods, without regard to type (e.g., yogurt, cheese, milk), largely based on theorized benefits of isolated nutrients for bone health (e.g., calcium, vitamin D) and theorized harms of isolated nutrients for cardiovascular diseases (CVDs) and obesity (e.g., total fat, saturated fat, total calories). However, advances in nutrition science have demonstrated that foods represent complex matrices of nutrients, minerals, bioactives, food structures, and other factors (e.g., phoshopholipids, prebiotics, probiotics) with correspondingly complex effects on health and disease. The present evidence suggests that whole-fat dairy foods do not cause weight gain, that overall dairy consumption increases lean body mass and reduces body fat, that yogurt consumption and probiotics reduce weight gain, that fermented dairy consumption including cheese is linked to lower CVD risk, and that yogurt, cheese, and even dairy fat may protect against type 2 diabetes. Based on the current science, dairy consumption is part of a healthy diet, without strong evidence to favor reduced-fat products; while intakes of probiotic-containing unsweetened and fermented dairy products such as yogurt and cheese appear especially beneficial.

Keywords: calories; dairy; dietary guidelines; microbiome; probiotics; vitamins; weight loss.

FIGURE 1

Why our infatuation with single nutrients? Although food and nutrition have been studied for centuries, modern nutritional science is surprisingly young. This timeline shows how scientific and geopolitical developments in the early 20th century together helped shape our understanding and led to a reductionist notion of food as a delivery vehicle for total calories and isolated nutrients. Adapted from reference with permission (open access).

FIGURE 2

Association of different foods and beverages with long-term weight gain or loss. Among 120,877 US adults in 3 separate cohorts followed for up to 24 y, with time-varying multivariable adjustment for age, sex, baseline BMI, sleep duration, smoking, physical activity, television watching, and all dietary factors jointly. HPFS, Health Professionals Follow-Up Study; NHS, Nurses’ Health Study; NHS2, Nurses’ Health Study 2. Adapted from reference with permission.

FIGURE 3

Relevant characteristics of dairy foods and selected molecular pathways potentially linked to cardiometabolic disease. Dairy foods are characterized by a complex variety of nutrients and processing methods that may influence cardiovascular and metabolic pathways. Examples of relevant constituents include specific fatty acids, calcium, and probiotics. Relevant processing methods may include animal breeding and feeding, fermentation, selection and cultivation of bacterial and yeast strains (e.g., as fermentation starters), and homogenization. Such modifications can alter the composition of the food (e.g., fermentation leads to production of vitamin K2 from vitamin K1) and its lipid structures (e.g., homogenization damages milk fat globule membrane), each of which can affect downstream molecular and signaling pathways. BCSFA, branched-chain saturated fats; GLP-1, glucagon-like peptide 1; MCSFA, medium-chain saturated fats; MFGM, milk fat globule membrane; MGP, matrix glutamate protein; mTOR, mammalian target of rapamycin; OCSFA, odd-chain saturated fats. Reproduced from reference with permission.