Does Milk Cause Constipation? A Crossover Dietary Trial

The aims of this study were to: (1) determine whether replacement of cow's milk protein with soy resolves Chronic Functional Constipation (CFC); and (2) investigate the effects of cow's milk beta casein A1 and cow's milk beta casein A2 on CFC. Children diagnosed with CFC were recruited to one of two crossover trials: Trial 1 compared the effects of cow's milk and soy milk; Trial 2 compared the effects of cow's milk beta casein A1 and cow's milk beta casein A2. Resolution of constipation was defined as greater than eight bowel motions during a two week intervention. Thirteen children (18 to 144 months) participated in Trial 1 (6 boys, 7 girls). Nine participants who completed the soy epoch all experienced resolution (p < 0.05). Thirty-nine children (21 to 144 months) participated in Trial 2 (25 boys, 14 girls). Resolution of constipation was highest during the washout epoch, 81%; followed by cow's milk beta casein A2, 79%; and cow's milk beta casein A1, 57%; however, the proportions did not differ statistically. The results of Trial 1 demonstrate an association between CFC and cow's milk consumption but Trial 2 failed to show an effect from type of casein. Some other component in cow's milk common to both A1 and A2 milk may be causing a problem in these susceptible children.