Almond protein and whey protein beverages elicit comparable appetite regulation, gastrointestinal symptoms and hydration responses in postmenopausal women: a randomised crossover trial.

INTRODUCTION: Postmenopausal women experience physiological changes in appetite regulation, gastrointestinal function and hydration that may influence utility of protein supplements. Almond protein powder (APP), a plant-derived by-product of almond oil extraction, provides protein alongside fibre and unsaturated fat, which may influence these outcomes differently from whey protein (WP). Objectives of this study were to compare acute appetite, gastrointestinal and hydration responses to APP, WP, placebo and water ingestion in postmenopausal women. MATERIALS AND METHODS: Nine postmenopausal women (60 ± 4 y) completed a randomised crossover trial involving four treatments: APP (29.5 g protein), WP (29.5 g protein), placebo and water. Appetite and gastrointestinal symptoms (GIS) were assessed over 180 min using visual analogue scales. Hydration outcomes included urine colour, urine specific gravity, urine and plasma osmolality, fluid balance and beverage hydration index (BHI). Outcomes were analysed using linear mixed models with significance accepted at p < 0.05. RESULTS: APP and WP suppressed appetite relative to baseline and water during the first 60 min post-ingestion period. Appetite area under the curve differed significantly between water and all other treatments (all p < 0.001), with APP, WP and placebo associated with lower appetite than water. GIS burden was low across all treatments, with no severe symptoms reported. Hydration markers demonstrated expected temporal changes; early dilution followed by progressive reconcentration. Significant treatment effects were observed for several hydration variables, including urine colour (p = 0.005), fluid balance (p < 0.001) and BHI (p = 0.017). Post-hoc comparisons identified differences between water and each nutrient-containing beverage for most hydration markers. CONCLUSION: APP and WP elicited comparable acute appetite suppression, gastrointestinal tolerance and hydration responses in postmenopausal women. While all nutrient-containing beverages reduced appetite relative to water during the early post-ingestion period, no meaningful differences were observed between APP and WP across appetite, GIS or hydration outcomes. These findings suggest that APP may represent a well-tolerated plant-based alternative to WP for protein supplementation in postmenopausal women. However, given the small sample size and acute nature of the intervention, larger and longer-term studies are required to determine whether these responses translate to habitual use and clinically relevant health outcomes. CLINICAL TRIAL REGISTRATION: Identifier 2024/HE000669; ACTRN12625000127404p. https://www.anzctr.org.au.