Minerals, vitamins and antioxidants

Milk contains many minerals, vitamins and antioxidants. The antioxidants have a role in prevention of oxidation of the milk, and they may also have protective effects in the milk-producing cell, and for the udder. Most important antioxidants in milk are the mineral selenium and the vitamins E and A. As there are many compounds that may have antioxidative function in milk, measurement of total antioxidative capacity of milk may be a useful tool [119].

Calcium

The calcium concentration in bovine milk is about 1 g/l (Table 1). Dairy products provide more than half of the calcium in the typical American diet [4], and daily intake of milk and milk products thus has a central role in securing calcium intake. In human nutrition adequate calcium intake is essential. Getting enough calcium in the diet gives healthy bones and teeth, and it may also help prevent hypertension, decrease the odds of getting colon or breast cancer, improve weight control and reduce the risk of developing kidney stones [4].

Selenium

The selenium concentration in body fluids and tissues are directly related to selenium intake. The selenium concentration in Scandinavian food is low, and the concentration in Norwegian bovine milk is about 11 ug/l (own results, 2006), and 37 ug/l in the US [9]. For plant products the situation is even worse; the selenium concentration in wheat flour (whole grain) is less than 20 ug/kg in Norwegian wheat (own results), compared to 707 ug/kg in the US [9].

Selenium is important in human health; it has a role in the immune- and antioxidant system and in DNA synthesis and DNA repair [120]. Selenoprotein P is an antioxidative defence enzyme having similar function as the selenoenzyme phospholipid hydro peroxide glutathione peroxidase (Gpx-4) inside the cells and it also protects LDL towards peroxidation [121,122]. A strong negative correlation between the concentration of selenium and the concentration of plasma lipid peroxidation products has been reported in a Canadian study [123]. These observation are in line with epidemiological observations from USA, where a strong negative correlation between mortality of ischemic cardiac disease and hypertension among men and women in the age group 55–64 years comparing states with different selenium intake [124,125].

Selenium protects against many (but not all) types of cancer [4]. There are indications that selenium may protect against asthma, and that low selenium intake may worsen the asthma symptoms [126]. Selenium deficiency has even been linked to adverse mood states [127]. Selenium is also a component of enzymes involved in metabolism of thyroid hormone.

As selenium is of fundamental importance to human health, the low selenium availability in Scandinavian soil is of concern. Different strategies can be used to increase human selenium intake, and addition of selenium-rich yeast to the feed of domestic animals is one option. Recommended daily intake of selenium is 55 ug [4], and the optimal selenium concentration in bovine milk may be discussed. If milk contains about 50–100 ug selenium/l, it would be a good selenium source.