Safety of milk-derived bioactive peptides.

Discipline: dairy and health; Key words: bioactive peptides, cytotoxicity, mutagenicity, immunomodulatory function, side effects.

Food-derived bioactive peptides are health-promoting substances which have regulatory functions in the human body beyond their normal nutritional contribution, hence they are part of what is defined as nutraceuticals. In milk and dairy products the biological activity of these peptides are latent until they are released by digestion in the gut, or fermentation of dairy products or enzymatic action on protein complexes. The health-promoting benefits of some of these bioactive peptides have been well studied, including: hypocholesterolemic, antithrombonic, antioxidant, antimicrobial, immunomodulatory opioid, mineral absorption and antihypertensive. What is less known is whether the consumption of laboratory or factory isolated bioactive peptides from milk and dairy products are safe for human consumption. In the review by Dr L.M. Beltrán-Barrientos and co-workers attention was given to several safety-associated components: cytotoxicity, mutagenicity, and possible adverse and side effects of bioactive peptides derived from milk. The review was published in the International Journal of Dairy Technology, Volume 17 of 2017, pages 16 to 22, the title being: Safety of milk-derived bioactive peptides.

Cytotoxicity caused by food proteins and peptides plays a significant role in regulation of human bodily functions and development and therefore in vitro methods have been developed to screen products derived from milk which may be concentrated to levels several fold those found in milk. At present there is no evidence that these products contribute to cytotoxicity. There is strong evidence though that bioactve peptides affect malignant cells, leaving normal cells unharmed which suggest that a cancer protective mechanism may exist. This is supported by studies on the milk protein lactoferrin which has been shown to inhibit intestinal tumours and possibly other tumours in the body.

The mutagenicity potential of hydrolysed casein and fermented milk has been studied by determining their ability to cause chromosomal aberrations in hamsters. No evidence was found in either short term or long term studies that hydrolysed casein or fermented milk caused chromosomal aberrations, changes in cell growth or polyploids.

Some individuals due to genetic make-up show reactions related to immunomodulatory function, particularly allergenicity. Milk proteins because of their diversity are most often implied. However, the incidence is relatively low as surveys have shown that allergenicity only develop in 2.2 to 2.8% of infants, of whom 85% outgrow the reactivity by four years of age. The allergic reaction is most often characterized by increased respiratory tract mucus production and asthma. In terms of side effects studies on products derived from milk bioactive peptides have shown no response in typical criteria such as dry cough, exanthemia, skin itching, dysgeusia, head ache or dizziness, and in general no adverse effects on skin, gastrointestinal, pulmonary or neurologic systems.

It was concluded that currently there is no evidence of toxicity or significant side effects which overwhelmingly suggest that the benefits of milk bioactive peptides outweigh the possible negative influences. The authors, though, do propose that more studies are needed as the literature available to the review was comparatively limited.