It’s common knowledge that dairy products are a rich source of several health-promoting nutrients, notably protein and calcium. But did you know that the different structures and textures of dairy products can have an impact on how much of these nutrients reach your bloodstream? That’s why fermented products such as yogurt may hold certain nutritional advantages over non-fermented dairy products. Greater understanding of dairy food structure and nutrient absorption could pave the way to developing innovative dairy products that improve the nutritional status of the elderly or people who are obese.
Much of what we know about healthy eating has come from studies of the health effects of single nutrients (e.g. protein, fat, vitamins, minerals). But we know now that the relationship between nutrition and health is much more complicated than that. For a start, we don’t eat single nutrients by themselves, but a mixture of whole foods. Studies have shown that the different structures and textures of dairy foods can determine how well nutrients are digested and absorbed by our bodies.
What is a food matrix?
Dairy foods are a complex mix of various nutrients and other components which together form the ‘food matrix’. There are three main types of dairy food matrix – liquid (milk and some fermented milks), semi-solid (yogurt and some fresh cheeses) and solid (most cheeses). The nutritional value of dairy foods depends not only on the nutrients they contain but also on their matrix structures, say the authors of this article.
The food matrix effect means that the nutrient content of a food does not necessarily predict its health properties. A good example is cheese. Although cheese contains a lot of saturated fat, which is linked to high levels of harmful fats in the blood and heart disease, studies have failed to show that cheese consumption increases the risk of heart disease.
What is bioavailability?
Not all the nutrients in the foods we eat are absorbed during their passage through our gut. Bioavailability refers to the proportion of a nutrient in the food that is absorbed into our bloodstream and is available for use by our bodies.
Processing methods may affect nutrient bioavailability in dairy foods
The processing methods involved in making the dairy products we eat can affect the bioavailability of nutrients. Fermenting milk to form yogurt or cheese releases, from proteins, some amino acids that can be absorbed directly, and may also improve protein digestion in the gut. Fermentation also seems to increase the solubility of calcium in the gut so that it’s more readily absorbed.
Firmer dairy products such as yogurt and cheese delay transit through the gut and are broken down less rapidly during digestion, and so the nutrients are absorbed more gradually and we may feel fuller for longer.
‘It is believed that lactic fermentation is responsible for the formation of new peptides during gastrointestinal digestion. Compared to milk, yogurt could also delay intestinal nitrogen delivery, but not final absorption.’ – Fardet et al, 2018.
Homogenisation of milk so that the cream does not separate reduces the size of the fat droplets. This increases the surface area on which fat-digesting enzymes can act, releasing more fatty acids that can be absorbed.
Understanding the dairy food matrix could improve nutrition
The matrix effect of dairy foods needs to be looked at more closely, say the authors. This knowledge could then be put to good use. Different dairy matrices may be better suited to particular groups of people. For example, elderly people may benefit from dairy foods that allow high levels of nutrients to be absorbed rapidly, whereas people who are obese may benefit from products that release nutrients more slowly.
‘Data collected show different kinetics of bioavailability of amino acids, fatty acids and calcium according to the physicochemical parameters of these [dairy] matrices, including compactness, hardness, elasticity, protein/lipid ratio, P/Ca [phosphorus/calcium] ratio, effect of ferments, size of fat globules, and possibly other qualitative parameters yet to be discovered.’ – Fardet et al, 2018.