Beijing Research Institute for Nutritional Resources, Beijing, China.
Clinical Nutrition Center, Huadong Hospital Affiliated to Fudan University, Shanghai, China.
Nutr J. 2017 Oct 25;16(1):72. doi: 10.1186/s12937-017-0275-0.
A major protein component of cow's milk is β-casein. The most frequent variants in dairy herds are A1 and A2. Recent studies showed that milk containing A1 β-casein promoted intestinal inflammation and exacerbated gastrointestinal symptoms. However, the acute gastrointestinal effects of A1 β-casein have not been investigated. This study compared the gastrointestinal effects of milk containing A1 and A2 β-casein versus A2 β-casein alone in Chinese adults with self-reported lactose intolerance.
In this randomised, crossover, double-blind trial, with a 3-day dairy washout period at baseline, subjects were randomised to consume 300 mL of milk containing A1 and A2 β-casein (ratio 58:42; conventional milk) or A2 β-casein alone; subjects consumed the alternative product after a 7-day washout period. Urine galactose was measured at baseline after a 15 g lactose load. Subjects completed 9-point visual analogue scales for gastrointestinal symptoms (borborygmus, flatulence, bloating, abdominal pain, stool frequency, and stool consistency) at baseline and at 1, 3, and 12 h after milk consumption.
A total of 600 subjects were included. All six symptom scores at 1 and 3 h were significantly lower after consuming A2 β-casein versus conventional milk (all P<0.0001). At 12 h, significant differences remained for bloating, abdominal pain, stool frequency, and stool consistency (all P<0.0001). Symptom scores were consistently lower with A2 β-casein in both lactose absorbers (urinary galactose ≥0.27 mmol/L) and lactose malabsorbers (urinary galactose <0.27 mmol/L).
Milk containing A2 β-casein attenuated acute gastrointestinal symptoms of milk intolerance, while conventional milk containing A1 β-casein reduced lactase activity and increased gastrointestinal symptoms compared with milk containing A2 β-casein. Thus, milk-related gastrointestinal symptoms may result from the ingestion of A1 β-casein rather than lactose in some individuals.
NCT02878876 , registered August 16, 2016. Retrospectively registered.
牛奶的主要蛋白质成分是β-酪蛋白。在奶牛群体中，最常见的变体是 A1 和 A2。最近的研究表明，含有 A1β-酪蛋白的牛奶会促进肠道炎症，并加重胃肠道症状。然而，A1β-酪蛋白的急性胃肠道影响尚未得到研究。本研究比较了含有 A1 和 A2β-酪蛋白的牛奶与单独含有 A2β-酪蛋白的牛奶对自述乳糖不耐受的中国成年人的胃肠道影响。
在这项随机、交叉、双盲试验中，在基线时有 3 天的奶制品清洗期，参与者被随机分配饮用 300 毫升含有 A1 和 A2β-酪蛋白（比例为 58:42；常规牛奶）或单独的 A2β-酪蛋白；在 7 天的清洗期后，参与者饮用另一种产品。在摄入 15 克乳糖负荷后，基线时测量尿液半乳糖。在基线和牛奶摄入后 1、3 和 12 小时，参与者完成 9 点视觉模拟量表，用于胃肠道症状（肠鸣音、胀气、腹胀、腹痛、排便频率和粪便稠度）。
共有 600 名参与者入选。在摄入 A2β-酪蛋白后，1 小时和 3 小时的所有六种症状评分均显著低于常规牛奶（均 P<0.0001）。在 12 小时时，腹胀、腹痛、排便频率和粪便稠度仍有显著差异（均 P<0.0001）。在乳糖吸收者（尿半乳糖≥0.27mmol/L）和乳糖吸收不良者（尿半乳糖<0.27mmol/L）中，A2β-酪蛋白的症状评分均持续较低。
含有 A2β-酪蛋白的牛奶减轻了乳糖不耐受的急性胃肠道症状，而含有 A1β-酪蛋白的常规牛奶与含有 A2β-酪蛋白的牛奶相比，降低了乳糖酶活性并增加了胃肠道症状。因此，在某些个体中，与牛奶相关的胃肠道症状可能是由于摄入 A1β-酪蛋白而不是乳糖引起的。
NCT02878876，2016 年 8 月 16 日注册。回顾性注册。
