Protein Yogurt vs. Whey in Strength-Trained Older Adults

We conducted an 8-week randomized intervention to compare whey protein (WP) powder with a high-protein yogurt (PY) as post-exercise supplements during supervised strength training in untrained older adults. Seventeen adults aged 60–70 years were assigned to consume either WP (25 g) or PY (24.5 g protein) three times per week in conjunction with a standardized strength-training program. Pre- and post-intervention assessments included body composition (BIA), muscle strength (10RM, isokinetic knee torque, handgrip), gait speed, resting metabolic rate, and gut microbiome profiling by 16S rRNA gene sequencing of fecal samples. Both groups increased skeletal muscle mass, strength, and gait speed, with no significant differences between WP and PY. Fat mass decreased only in the WP group, whereas resting metabolic rate increased only in the PY group. Gut microbiome analyses revealed distinct compositional and predicted functional shifts: WP increased the Firmicutes/Bacteroidota ratio and enriched Subdoligranulum, while PY increased alpha diversity and the abundance of Coprococcus. Overall, protein yogurt and whey protein similarly supported improvements in muscle and functional outcomes during strength training, but induced different microbiome responses, suggesting that protein yogurt may be a cost-effective alternative to whey with potential additional benefits for gut health in older adults.