Main idea: The results suggest that the partial hydrolyzation of milk proteins (mainly casein) reduces subjective symptoms to some extent in subjects with functional gastrointestinal disorders. The mechanism remains to be resolved.
Unspecified gastrointestinal symptoms associated with milk consumption are common. In addition to lactose also other components of milk may be involved. The current research studied whether the partial hydrolyzation of milk proteins would affect gastrointestinal symptoms in subjects with functional gastrointestinal disorders. In a randomized, placebo-controlled crossover intervention, subjects (n = 41) were given ordinary or hydrolyzed high-protein, lactose-free milkshakes (500 mL, 50 g protein) to be consumed daily for ten days. After a washout period of ten days, the other product was consumed for another ten days. Gastrointestinal symptoms were recorded daily during the study periods, and a validated irritable bowel syndrome-symptom severity scale (IBS-SSS) questionnaire was completed at the beginning of the study and at the end of both study periods. Blood and urine samples were analyzed for markers of inflammation, intestinal permeability, and immune activation. Both the IBS-SSS score and total symptom were significantly reduced when participants consumed the hydrolyzed product. Less bloating was reported during both study periods when compared with the baseline (p < 0.01 for both groups). Flatulence (p = 0.01) and heartburn (p = 0.03) decreased when consuming the hydrolyzed product but not when drinking the control product. No significant differences in the levels of inflammatory markers (tumor necrosis factor-alpha, TNF-α and interleukin 6, IL-6), intestinal permeability (fatty acid-binding protein 2, FABP2), or immune activation (1-methylhistamine) were detected between the treatment periods.