The study, which was funded by The a2 Milk Company, monitored the gastrointestinal symptoms of 600 Chinese adults with self-reported lactose intolerance and digestive discomfort after drinking milk.
The double blind, randomized, cross-over study, subjects were given milk containing A1 and A2 beta casein (conventional milk) and A2 beta casein milk (provided by The a2 Milk Company) in randomized treatment sequences: receiving conventional milk on the first day and milk containing A2 beta casein on the eighth day, or vice versa, according to the study.
Subjects used a food diary to record milk intake and completed a visual analogue scale (VAS) to monitor their gastrointestinal symptoms after one hour of consuming the milk sample. After three hours, subjects provided a urine sample and another VAS for gastrointestinal symptoms.
The subjects continued a dairy-free diet for seven days and on day eight, returned to the study site to repeat the study procedures and consume the corresponding milk product.
Gastrointestinal symptoms (bloating, abdominal pain, stool frequency, etc.) scores were graded on a numeric scale at three different times -- one,
three, and 12 hours following consumption of each milk sample.
The combined results of the gastrointestinal reactions of all participants after consuming conventional milk ranged between 0 and 3 (0=no discomfort), and A2 β-casein milk symptoms scores ranged between 0 and 2.
"The symptom scores for all six symptoms were consistently lower with milk containing A2 β-casein than with conventional milk at both 1 and 3 h after consumption," researchers said.
“These findings suggest that, in some individuals with self-reported lactose intolerance, the adverse gastrointestinal symptoms following milk intake might be related to the presence of A1 β-casein in milk rather than lactose itself.”
Source: Nutrition Journal
“Effects of cow’s milk beta-casein variants on symptoms of milk intolerance in Chinese adults: a multicentre, randomised controlled study”
Authors: Mei He, et al