Acute Sensory And Gastrointestinal Responses To Protein Intake Prior To Resistance Training

Muscle mass is an important variable for health, daily life and sports performance. Protein consumption throughout the day is often recommended to stimulate muscle mass synthesis. However, given that palatability and potential gastrointestinal symptoms (GIs) may be factors that influence voluntary intake, any protein-rich products recommended for exercisers must be viable, convenient, and pleasant. PURPOSE: To compare the palatability of two protein-rich products before starting resistance exercise and potential GIs that may arise during exercise after their consumption. METHODS: Twenty-five physically active subjects visited the laboratory on two occasions. During each visit, a protein-rich product was consumed (a 200 mL liquid Greek yogurt, 25 g protein; or a 500 mL milk, 24 g protein) before completing a standardized resistance-exercise session. Consumption time (CT) and six palatability aspects (1-9 scale) were assessed. 17 GIs were reported (0-9 scale) before and after product consumption, halfway through and at the end of each session. RESULTS: Products were not different in the palatability variables; overall acceptance was 7.64 ± 0.99 (mean ± SD) for yogurt and 7.84 ± 0.85 for milk (p = 0.134). CT was greater for milk (370.6 ± 289. 47 s) than yogurt (171.12 ± 81.84 s) (p ≤ 0.01). Most GIs were mild or moderate with no difference between products, ranging from 0-4. Most severe were thick saliva (0-9, min-max) with 1.25 ± 1.91 for yogurt and 1.17 ± 1.92 for milk (p > 0.05), and burping (0-9, min-max) with 1.01 ± 1.63 for yogurt and 1.41 ± 1.78 for milk (p > 0.05). Only nausea, thick saliva, burping, and intestinal cramps increased with time and similarly for milk and yogurt; the urge to urinate was higher for milk (0.49 ± 0.17; 0-3, min-max) than for yogurt (0.14 ± 0.10; 0-5, min-max) (p = 0.012). Finally, abdominal bloating increased over time with milk from 0.16 ± 0.47 (0-2, min-max) before product consumption to 1.08 ± 2.3 (0-9, min- max) at the end of the session, but not with yogurt (p = 0.01 for the interaction). CONCLUSION: Both products showed good acceptance and reasonable tolerance, hence they could be considered as options for protein intake before resistance training.Funded by Dos Pinos Milk Producers Coop. of Costa Rica under a cooperation agreement with University of Costa Rica for research project VI-838-C4-326.