A great deal of effort is put into “humanizing” milk formulas; this is mainly achieved by adjusting the casein-to-whey ratio to mimic that of human milk. We have shown above that significant differences exist between the milks of human, chimp, mouse, and cow. Therefore, we wanted to investigate if significant differences exist in the AA composition of human milk proteins versus bovine milk proteins compared with the differences observed over the full genome of human versus cow. More importantly, we wanted to know which AA exhibited the greatest degree of change between human and cow. To address this question, we subtracted the frequency of each AA in human from its frequency in cow. We carried out this approach first for all milk proteins and second for all nonmilk proteins (see Methods).