Protein distribution, quantity and quality is optimized by protein intervention in frail community-dwelling older adults during resistance training: a randomized controlled trial

Protein interventions are widely implemented alongside resistance training in older adults. However, research has mainly focused on increasing protein intake, while changes in protein distribution and protein quality remain insufficiently explored. Therefore, this randomized controlled trial investigated the effect of a protein intervention consisting of dietary counselling and protein supplementation during resistance training on protein distribution, quantity and quality in frail community-dwelling older adults. This secondary analysis included 295 frail community-dwelling older adults (mean age 73.9 ± 6.0, 69% female) into a twelve-week resistance training only (control; n = 146) or resistance training with a protein intervention ( n = 149). The protein intervention group received dietary counselling and daily provision of whey protein supplements (20 g) to support achieving a protein intake of 1.2–1.5 g/kg/day. Dietary intake was measured using 3-day dietary record. Protein quality was assessed using the meal protein quality score per eating occasion and a score of > 100 indicates adequate protein quality. Linear mixed models were used to examine the between-group (intervention) effects ( p < 0.05). At follow-up, protein intake was significantly higher in the protein intervention group than in the control group with an adjusted between-group difference of 29.1 g/day ( p < 0.001). Between-group differences at follow-up in protein intake were observed across all eating occasions (breakfast: 9.1 g/day, first snack: 2.4 g/day, lunch: 5.2 g/day, second snack: 2.3 g/day, dinner: 3.2 g/day, evening snack: 7.4 g/day; all p ≤ 0.028). At follow-up, overall protein quality was significantly higher in the protein intervention group than in the control group (33.8 points, p < 0.001), as well as at all eating occasions (all p ≤ 0.005). The differences in protein intake were primarily attributable to protein supplements, eggs, cheese, and milk products. At follow-up, energy and fat intake were significantly higher in the protein intervention group than in the control group (208.9 kcal/day, p < 0.001; 7.3 g/day, p = 0.022, respectively). No significant between-group difference was observed for carbohydrate intake. The protein intervention, combining dietary counselling with protein supplementation, improved protein quantity and quality, especially at typically protein-poor eating occasions, such as breakfast, lunch, and evening snack. The higher protein intake observed after twelve weeks was mainly attributed to the protein supplements. NL-OMON54919 (at ICTRP Search Portal), date of registration: 09-02-2021.