Author’s response to reviews Title: Effects of cow's milk beta-casein variants on symptoms of milk intolerance in Chinese adults: a multicentre, randomised controlled study

4. -"... conventional milk reduced lactase activity and..." Can you really say that conventional milk reduced lactase activity? According to Table 5, urinary galactose concentrations increased after consumption of both milk relative to baseline. Reply: Table 5 shows that, although both A1/A2 and A2 milk increased galactose levels, the greater change from baseline was seen for milk containing A2 β-casein only in most cases. In accordance with the reviewer's comment, this sentence was revised as follows (line 45–47): “Milk containing A2 β-casein attenuated acute gastrointestinal symptoms of milk intolerance while conventional milk containing A1 β-casein reduced lactase activity... compared with milk containing A2 β-casein.” 5. "galactose absorbers and malabsorbers", should be lactose absorbers and malabsorbers Reply: We thank the reviewer for this comment and have revised this throughout the manuscript as suggested. 6. Urinary galactose (page 7): No reference is given for the method for the analysis of urinary galactose. Where does the cut off value 0.27 mmol/l, which was used to divide the subjects into lactose absorbers and malabsorbers come from? Please provide references. Reply: Participants are classified as lactose malabsorbers if they have a urinary galactose concentration <0.9 mmol/L after a 50-g oral lactose intake. In our study, subjects ingested 15 g of lactose (corresponding to 300 ml of regular milk). Therefore, we used 0.9*(15/50)=0.27 mmol/L as the threshold to distinguish lactose absorbers from malabsorbers. We have now explained this in the revised manuscript (lines 179–182 and cited the following two references in support of this: [13] Reha Artan, Zafer Bicakci, Fahri Isitan. Urinary lactose tolerance test for the detection of lactose malabsorption. Turk J Gastroentero 1998; 9 (4): 361-365. [14] Riitta Korpela. Symptoms of “lactose intolerance”. Scandinavian Journal of Nutrition 2001; 45: 171-173. 7. Were galactose concentrations adjusted for urinary creatinine? Reply: Galactose concentrations were not adjusted for urinary creatinine, and urinary creatinine was not measured. Importantly, for the duration of this study, equivalent volumes of milk/liquid were consumed by study subjects; therefore, we believe no adjustment should be necessary.