HEALTH ASSOCIATED FUNCTIONS OF MILK AND DAIRY FOODS

Discipline: dairy & health; Key words: gouda-type cheese, glucose tolerance, dairy food intake, cognitive function, cow’s milk oestrogen, cancer.

Milk and dairy products always seem to be under barrage when it comes to health issues, sometimes negative sometimes positive! Thus, one continuously observes research papers to that effect. Positively though, one remains amazed by the nutraceutical possibilities and other benefits that are discovered. For example, Dr Uenishi and co-workers recently discovered that a water-soluble extract of a gouda-type cheese showed inhibitory activity of the enzyme dipeptidyl-peptidase 4 (DPP-4), which in a rat model improved glucose tolerance in type 2 diabetes [H. Uenishi et al., 2012. International Dairy Journal, Volume 22, pages 24 to 30; Isolation and identification of casein-derived dipeptidyl-peptidase 4 (DPP-4)-inhibitory peptide LPQNIPPL from gouda-type cheese and its effect on plasma glucose in rats].

Two other studies in the same volume of this journal are intriguing. The one is on cognitive behaviour and the other on oestrogens, the references respectively: G.E. Crichton et al., 2012. International Dairy Journal, Volume 22, pages 15 to 23: Relation between dairy food intake and cognitive function: The Maine-Syracuse Longitudinal Study, and P.W. Parodi, 2012. International Dairy Journal, Volume 22, pages 3 to 14: Impact of cows’ milk estrogen on cancer risk.

Diet may play a role in modification of age-related function, one being by altering the course of age-related cognitive decline.  Observational findings suggest that dairy food intake may be positively related to cognitive function in young children, but overall information is limited. The aim of the study of Dr Crichton and co-workers was therefore to investigate whether dairy food intake in 972 aged study participants is associated with cognitive function, before and after adjustment for cardiovascular, lifestyle and dietary factors. It was determined that participants who consumed dairy products at least once per day had significantly higher scores on multiple domains of cognitive function compared with those who never or rarely consumed dairy foods. The underlying causal mechanisms, however, are still to be determined.

Oestrogens (e.g oestradiol) have been implicated in cancer at sites which respond to hormone action, such as the breast, ovaries, endometrium and the prostate. Because cow’s milk contains oestrogens, some authors have suggested that its consumption may contribute to the risk of cancer at these sites. However, Dr Parody in his review argued that these authors did not recognize the complex mechanisms these sites possess to regulate oestradiol levels. Hormone-responsive and many other cells contain all the necessary enzymes for manufacturing of oestradiol from abundantly present precursors and for inactivation of unwanted oestrogens. Oestradiol from dairy products is extensively inactivated in the gastro-intestinal tract and only about 5% survive absorption to the liver. This implies that daily dairy product intake would supply only about 0.25% of the FAO/WHO upper acceptable daily intake of oestradiol. Therefore, according to Dr Parody, the epidemiological evidence thus far does not suggest an association between dairy product consumption and risk of cancer at these sensitive sites.