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Session: Amino Acid and Protein Metabolism (Oral 6)

(OR06-04-24) Healthy Older Adults Consuming the Protein RDA Show Similar Whole-Body Protein Kinetics While Consuming Vegan and Lacto-Vegetarian Diets

Saturday, June 29, 2024
5:36 PM – 5:48 PM CT
Location:  W183
Objectives: Dairy products are sources of high-quality proteins (i.e., rich in essential amino acids – EAA) and are commonly incorporated in flexible vegetarian diets to improve overall protein quality. However, no previous studies have measured the impact of replacing part of a 100% plant-based diet (i.e., vegan) with dairy on whole-body protein kinetics in older persons. We hypothesized that replacing plant-based protein sources with dairy-source proteins would enhance the whole-body anabolic response to meals.

Methods: In this study, twelve (n=5 males and n=7 females) healthy older participants (71± 3 years) were put on two different 17-day vegetarian diets, each providing the recommended dietary allowance (RDA) for protein (0.8 g/kg/day). One diet was entirely plant-based (Vegan - V), while the other included 2-3 servings of dairy (e.g., whole milk and cheeses) to replace a portion of the plant-based protein sources (Lacto-vegetarian - LV). The order of the diets was randomized, with a 7-day washout period in between. All food was provided. Body composition (DXA), food intake, and physical activity (accelerometry) were monitored. On the last day of each diet, a 16-hour metabolic study was conducted to measure whole-body protein kinetics using IV infusion of amino acids labelled with stable isotopes (tracers). Blood samples were collected throughout the metabolic study days to measure the concentration of fasting and post-prandial essential amino acids (EAA) and tracers.

Results: Eleven participants successfully consumed the RDA for protein daily during both diets. No significant changes were observed in body composition. Dairy sources accounted for 32.8 ± 0.2% of the daily protein during the LV diet. However, there were no significant differences in plasma EAA profiles between conditions (AUC: V = 15424 ± 1850 vs. LV = 15101 ± 1940 μmol/L/960min-1), whole-body protein synthesis, breakdown, or net protein balance when comparing the V vs LV metabolic conditions.

Conclusions: Contrary to our initial hypothesis, replacing plant-based protein sources with 2-3 servings of dairy did not increase whole-body anabolic response to meals in healthy older adults consuming the RDA for protein. Further analyses may reveal different responses at the skeletal muscle level.

Funding Sources: US National Dairy Council and Dairy Farmers of Canada