Recruitment:~Flyers, emails, and advertisements in local and university newspapers will be used for recruitment of study participants.~Phone screening:~Interested individuals will be contacted via phone by study staff to assess eligibility by asking questions listed in the inclusion and exclusion criteria.~Informed consent:~If the individual is eligible through phone screening, the study staff will read and explain the informed consent to the individual. Informed consent will contain all the information regarding study procedure, compensation, risks and benefits. If Informed Consent is granted, the participant will be contacted through their preferred method of contact (email or phone) to schedule a hydrogen breath test (HBT).~Screening lactose maldigesters via HBT:~Maldigestion will be classified by a rise of breath hydrogen concentration of greater than 20ppm after a challenge dose of 2% commercial milk containing 0.5g lactose per kg body weight. Participants will consume a low-fiber meal and then fast 12 hours prior to HBT. A breath sample will be obtained from participants just before drinking the milk dose. Participants will then consume milk containing 0.5 grams lactose per kilogram body weight. Breath samples will be obtained according to the following schedule: 0 hour (pre dose), 30 minutes, 1 hour, 90 minutes, 2 hours, 3 hours, 4 hours, 5 hours and 6 hours. Participants who exhibit a rise of breath hydrogen concentration of greater than 20ppm between any two timepoints of the 6-hour test will be classified as lactose maldigesters, and will be qualified to enter the intervention portion of the study.~Intervention:~There will be two in-person visits in intervention. The visits will be at least 6 days apart.~Visit 1:~Participants will consume a low-fiber dinner and fast for 12 hours prior to the visit. Participants will provide their first breath sample before consumption of milk. Participants will then consume a challenge dose of first randomized milk containing 0.5g lactose per kg body weight. Breath samples will be collected at 0 hour (pre dose), 30 minutes, 1 hour, 90 minutes, 2 hours, 3 hours, 4 hours, 5 hours and 6 hours. Participants will be asked to report and rate any symptoms including abdominal pain, bloating, flatulence, fecal urgency, and diarrhea they might experience during the 6 hour test.Blood will be drawn from participants at 0 hour (pre-dose), 1 hour , 2 hours and 3 hours time-point via catheter and serum will be isolated from whole blood for analyses of markers including hs-CRP, IgG, IgG1, Il-4, GSH and BCM-7.~Visit 2:~There will be at least a 6-day interval between Visit 1 and Visit 2. The same procedure from visit 1 will be followed in visit 2. Participants will consume the second randomized milk containing 0.5 grams lactose per kilogram body weight during this visit.
Cow's milk contains two types of β-casein: A1 and A2. It is evident from human clinical trials that milk with A1 protein produces more hydrogen and symptoms of lactose intolerance. A pro-inflammatory μ-opioid peptide BCM-7 is released from A1 but not from A2. Milk containing A1 β-casein produced more inflammatory markers than A2 β-casein. This is a double-blinded, randomized, controlled trial conducted to determine if A1 beta-casein containing milk causes acute effects on inflammatory markers following a single milk feeding, as compared to milk containing only A2 beta-casein.