USDA researchers recently found that breeding to “improve” wheat varieties over the past 130 years (a period during which yields of grain per acre tripled) had reduced levels of iron by 28 percent and zinc and selenium by roughly a third. Similarly, milk from modern Holstein cows (in which breeders have managed to more than triple daily yield since 1950) has considerably less butterfat and other nutrients than that from older, less “improved” varieties like Jersey, Guernsey, and Brown Swiss.
