Comparison of the impact of bovine milk ß-casein variants on digestive comfort in females self-reporting dairy intolerance: a randomized controlled trial.

BACKGROUND: Lactose malabsorption (LM) is a major cause of digestive discomfort from dairy products. Recently, a role for bovine ß-casein A1 has been proposed. OBJECTIVES: We examined whether there are distinct symptoms of digestive discomfort due to either lactose or differing bovine ß-casein types. METHODS: Women (n = 40; age: 25.2 ± 0.5 y) with self-reported varying dairy tolerance underwent a 50-g lactose challenge. Based on postchallenge LM and digestive discomfort, participants were classified as either lactose intolerant (LI; n = 10, self-reported intolerant, diagnosed lactose intolerant), nonlactose dairy intolerant (NLDI; n = 20, self-reported intolerant, diagnosed lactose tolerant), or dairy tolerant (DT; n = 10, self-reported tolerant, diagnosed lactose tolerant). In a double-blinded randomized sequence, participants consumed 750 mL conventional milk (CON; containing A1 and A2 ß-casein and lactose), a2 Milk (A2M; exclusively containing A2 ß-casein with lactose), or lactose-free conventional milk (LF-CON; containing A1 and A2 ß-casein without lactose). Subjective digestive symptoms and breath hydrogen (measuring LM) were recorded regularly over 3 h, and further ad hoc digestive symptoms over 12 h. RESULTS: LI subjects experienced prolonged digestive discomfort with CON milk. A2M reduced (P < 0.05) some symptoms (nausea: A2M 8 ± 3 mm compared with CON 15 ± 3mm; fecal urgency: A2M 4 ± 1 compared with CON 10 ± 3 mm), and attenuated the rise in breath hydrogen over 3 h, relative to CON milk (A2M 59 ± 23 compared with CON 98 ± 25 ppm at 150 min; P < 0.01). In contrast, NLDI subjects experienced rapid-onset, transient symptoms (abdominal distension, bloating, and flatulence) without increased breath hydrogen, irrespective of milk type. CONCLUSIONS: In LI individuals, LM and digestive comfort with lactose-containing milks was improved with milk containing exclusively A2 ß-casein. Furthermore, self-reported dairy intolerance without LM (NLDI) is characterized by early-onset digestive discomfort following milk ingestion, irrespective of lactose content or ß-casein type. This trial was registered at www.anzctr.org.au as ACTRN12616001694404.

Dairy intolerance syndrome in Iranian young adult.

BACKGROUND: Dairy products intolerance is defined by existing of gastrointestinal symptoms following dairy product consumption. Its prevalence varies among different countries. This study is conducted to determine the frequencies and severities of intolerance symptoms in the consumption of different dairy products in Iranian students of Medical Sciences. METHODS: In this cross-sectional study, 1041 students from Isfahan University of Medical Sciences who apparently were healthy and had not used any drug before, participated. The questionnaire included information about dairy product consumption and avoidance, severity of dairy intolerance symptoms included gas passing, flatulence, diarrhea and abdominal pain and coexistence of irritable bowel syndrome (IBS) RESULTS: The frequencies of dairy intolerance syndromes in milk, yoghurt, cheese and ice cream consumption were 51.1% (532), 16.6% (173), 11.7% (122) and 13.4% (140), respectively. Most severe symptoms for milk, yoghurt, cheese and ice cream intolerance were diarrhea (2.11 ± 0.08), gas passing (1.56 ± 0.09) and flatulence (1.49 ± 0.09), respectively. Fifty (9.4%) of symptomatic respondents never drank milk. Correlation coefficient between symptoms severity and the avoidance of consumption in milk intolerance was 0.38. CONCLUSIONS: Students tolerate other dairy products better in comparison with milk. In the present study, the phenomenon as irritable bowel syndrome was not strongly associated with the severity of all symptoms in dairy intolerant persons. Also, there were weak association between the severity of symptoms with dairy consumption and avoidance, but more studies are needed to evaluate calcium absorption and osteoporosis in symptomatic cases.