By Harold McGee
Nearly all milks contain the same battery of nutrients, the relative proportions of which vary greatly from species to species. Generally, animals that grow rapidly are fed with milk high in protein and minerals. A calf doubles its weight at birth in 50 days, a human infant in 100; sure enough, cow’s milk contains more than double the protein and minerals of mother’s milk. Of the major nutrients, ruminant milk is seriously lacking only in iron and in vitamin C. Thanks to the rumen microbes, which convert the unsaturated fatty acids of grass and grain into saturated fatty acids, the milk fat of ruminant animals is the most highly saturated of our common foods. Only coconut oil beats it. Saturated fat does raise blood cholesterol levels, and high blood cholesterol is associated with an increased risk of heart disease; but the other foods in a balanced diet can compensate for this disadvantage.