Mineral composition of cow milk - а mini review

Milk is a secretory product of the mammary glands which synthetic capacity is extremely high at the peak of lactation. Cow's milk is a generally recognized source of Ca, K, Mg, Na, P, Se, and Zn for human nutrition. About 50 mineral elements were found in milk (A.V. Skalny, 2019). Given the fact that the deficiency of micro- and macroelements is becoming global (R.L. Bailey, 2015; A.V. Skalny, 2019), interest in milk to solve this problem is increasing (M.L. Astolfi, 2020). Milk is the only source of nutrients for newborn calves. The composition and proportions of milk components are optimal for their gastrointestinal absorption, which ensures the successful survival of the species. The quantity and structural composition of macro- and microelements of milk are complementary to active anabolism and the development of the musculoskeletal system, in particular the skeleton of young animals. The purpose of our review is to summarize relevant data on micro- and macroelements in milk with regard to their biological role in cows. Comparative analysis shows a wide range of mineral content of milk. The content of Zn can vary from 3.09 to 6.48 mg/kg, Cu from 0.83 to 1.73 mg/kg (S.M. Zain, 2016; S. Kinal, 2007). This may be due to i) alimentary factors (A. Costa, 2021) which are closely related to the natural distribution of micro- and macroelements in the Earth’s crust (S.M. Zain, 2016) and ii) synergistic and antagonistic interactions of elements in their assimilation (N. Bortey-Sam, 2015; A.V. Skalny, 2019). For example, an excess of potassium and calcium reduces the absorption of magnesium and phosphorus (A.V. Skalny, 2019), and a deficiency of vitamin D disrupts the absorption of Ca (W.P. Weiss, 2017). We also note the variability of the mineral content depending on the lactation period, season of the year (S.M. O’Kane, 2018; E.S. Kandinskaya, 2019), type of housing and feeding (V.S. Kozyr, 2015; I. Orzhales, 2018). Milk iodine and selenium concentration measured by inductively coupled plasma mass spectrometry were higher than indicated in previously created food composition databases (S.M. O’Kane, 2018). Thus, reliance on previously created databases should be partial when choosing milk as a source of mineral components to compensate for the identified deficiency in the human diet. Newly formed databases should be more accessible to the consumer. In addition, molecular tools should help to identify target genes and proteins as markers for assessing the level of macro- and microelements (W.P. Weiss, 2017; A. Costa, 2021), but so far little progress has been made in this research area. Precise elemental analysis of milk is necessary both to confirm its safety in terms of toxic macro- and microelements, and to solve the mineral deficiency problem.