This is a myth. Drinking cow’s milk will not make your breast milk better. In Japan, they did comparative study between infants fed by mother’s breast milk vs. cow’s milk formula. This study showed that breast milk was more superior in vision development, brain development, less food and skin allergy (Atopic Dermatitis), and less incidence of diabetes type I (autoimmune disease). However, subsequent repeat of the study a decade later did not show any significant difference between mother’s breast milk vs. formula. This really puzzled the researchers. Superficial observation could conclude that newer formula is as good as breast milk. However, when researchers looked into the lifestyles and diets of the mothers, they noted a unique difference. They found that the mothers from the newer study were more americanized and they were consuming much more dairy on daily basis compared to mothers on the initial study, who were consuming traditional japanese food not containing much dairy. In my opinion, this shows that drinking cow’s milk will decrease the quality of the breast milk!