The effects of dietary nitrate ingestion on physical performance tests in 50–65 years old postmenopausal women: A pilot randomized, double-blind, placebo-controlled, and crossover study

Background & aims: The post-menopausal period represents a noteworthy stage in a woman's life characterized by hormonal shifts that can influence diverse biological processes encompassing energy metabolism and physical performance. NO₃⁻ effects on physical performance in 50–65 years old postmenopausal women after short-term supplementation remain unknown. 

Methods: This is a randomized, double-blind, placebo-controlled, crossover study. After two sessions in non-consecutive days of familiarization tests, fifteen post-menopausal women aged between 50 and 65 were enrolled in this study. The trial consisted of two eight-day arms: a) NO₃⁻ −70 mL of beetroot juice (BRJ) with ˜400 mg of NO₃⁻, and b) placebo (PLA) −70 mL of BRJ NO₃⁻ depleted. Both interventions were obtained from the same manufacturer's product, presenting the same organoleptic properties. After this period, five physical performance tests (handgrip strength, arm curl, sit-to-stand, agility and dynamic balance and 6-min walk test (6MWT)) were applied. 

Results: Fourteen participants completed all experimental protocols, including a minimum seven-day washout period between protocols. NO₂⁻ plasma concentrations were consistently elevated in the NO₃⁻ condition at 0.41 (0.40) μM compared to the PLA at 0.18 (0.18) μM (p < 0.001). The 6MWT showed higher values in BRJ with NO₃⁻ condition (19.6 m [95%CI: 1.33 to 37.88]; p = 0.038), while the other physical performance tests did not show significant difference between conditions (p > 0.05). 

Conclusions: Our findings suggest benefits in the physical performance of activities with longer durations, indicating that the adaptation caused by ingestion of NO₃⁻ may be related to the cardiorespiratory capacity.