Milk, dairy products and cheeses they are important elements of our diet and provide essential nutrients for our psycho-physical well-being. Beyond the important role they play as sources of calcium highly assimilable, their importance in the diet is also linked to the contribution of specific strategic nutrients contained in both the protein and lipid components of these foods.
The protein degradation process, which occurs during cheese ripening, plays a particularly important role from a nutritional point of view, determining both an increase in the digestibility of the protein due to the increase in free amino acids and the release of bioactive peptides, i.e. peptides which have a beneficial action on human health by exercising antihypertensive, antimicrobial, opioid, antioxidant, immunomodulatory, and mineral element binding activity.
In the case of cheeses, the proteolytic activity originates both from enzymes naturally present in milk and from enzymes contributed by lactic acid bacteria or from exogenous sources, which, overall, contribute to the generation of bioactive peptides. The release of these peptides also occurs during the enzymatic hydrolysis connected with the intestinal digestion of milk proteins. For some of these peptides it has already been demonstrated effective antihypertensive action in randomized clinical trials.
Milk lipids are often remembered only for the content of saturated fatty acids, believed to have a negative effect on cardiovascular pathologies, forgetting that milk fat contains many others fatty acids, even unsaturated, which have been ascertained to have a positive effect on human health. The content of bioactive substances in milk fat can be suitably enhanced through natural feeding systems that respect animal welfare, such as those based on pasture. Numerous researches have focused on the enrichment of milk with fatty acids of which specific bioactive properties are known; among these are vaccenic acid (VA, C18:1 t11), conjugated linoleic acid (CLA, C18:2 c9t11) and α-linolenic acid (ALA, C18:3n-3).
CLA is a fatty acid with numerous biological functions, but the most important are the anticancer one (confirmed for the moment only on laboratory animals and cell cultures), anti-inflammatory and anti-cholesterolemic. CLA is a functional component of ruminant milk and, in this sense, cheeses are considered one of the most important food sources in the human diet. Sheep's milk, compared to bovine milk, contains 3-4 times higher quantities of VA and CLA, because, in the case of dairy sheep, breeding systems based on pasture are more widespread.
Cheeses with high CLA contents are also characterized by high VA contents. The biological role of VA, for many years, was considered negatively, given the belonging of this substance to the category of trans fatty acids, of which their cholesterol-lowering effect is known. However, recent studies have shown that VA is able to perform a synergistic action with CLA in the control of blood cholesterol.
Sheep's cheese also contains moderate amounts of ALA, on average double those found in bovine cheeses. This fatty acid, in addition to playing the role of precursor of the other longer chain omega-3 polyunsaturated fatty acids, has an independent bioactive action, also recognized by EFSA, which has also set recommended daily intake values (RDA, 2g/d), so that a control action on plasma cholesterol can be carried out. The great interest of research for these fatty acids with bioactive action has found an important confirmation in the results of clinical studies that evaluated the effect of pecorino enriched in VA, CLA and ALA on humans.
For example, in clinically healthy subjects, the consumption of 200 g/week, for ten weeks, of a pecorino with medium-high contents of VA and RA (3,26 and 1,56 g/100 lipids, respectively), compared a control cheese with lower VA and RA concentrations (0,4 and 0,19 g/100 lipids, respectively), reduced the blood concentration of pro-inflammatory cytokines (Sofi et al., 2010). The consumption of 90 g/d for three weeks of pecorino naturally enriched in VA, CLA and ALA (respectively 6,3; 2,5 and 2,1 g/100 g of fat) compared to a control pecorino (respectively 1,7, 0,8 and 0,6 g/100 g of fat), reduced blood LDL cholesterol concentration by 7% in hypercholesterolaemic individuals and induced a marked reduction in the blood concentration of an endocannabinoid called anandamide, which is thought to be involved both in the inflammatory response and, more generally, in dyslipidemic phenomena (Pintus et al., 2013).
Based on the scientific evidence that has accumulated over the past 15 years, it would appear that the overall balance of the effect relating to the various lipid molecules contained in milk and cheese is completely positive, rehabilitating milk fat, compared to the negative evaluation that accompanied it for many years.
