Highlight
• Eight weeks of daily nitrate-rich beetroot extract supplementation significantly increased fasting nitrate and nitrite levels in postmenopausal women.
• Improved maximal knee extensor torque (muscle strength) was observed after long-term supplementation.
• Muscle power enhancements were particularly evident at specific angular velocities, indicating improved contractile muscle function.
• No evidence of nitrate tolerance was seen over the study duration, supporting the safety and efficacy of prolonged supplementation.
Study Background and Disease Burden
Menopause is characterized by a substantial decline in circulating estrogen levels, which results not only in classic vasomotor symptoms but also significantly impacts skeletal muscle function and quality of life. Reduced estrogen correlates with impaired nitric oxide (NO) bioavailability, a critical signaling molecule involved in vasodilation, mitochondrial efficiency, and muscle contractility. The decline in NO may contribute to the progressive loss of muscle strength and power seen in postmenopausal women, increasing risks of frailty, falls, and functional disability.
Dietary nitrate, particularly from beetroot, is an established precursor to NO via the enterosalivary nitrate-nitrite-NO pathway. Acute ingestion of nitrate-rich beetroot products has demonstrated improved NO bioavailability and muscle function in older adults; however, evidence on prolonged supplementation beyond two weeks remains limited. Understanding the long-term effects is clinically relevant to develop nutritional interventions that may mitigate muscle decline in this vulnerable population.
Study Design
This study was a randomized, double-blind, placebo-controlled, parallel-group trial assessing the impact of eight weeks of dietary nitrate supplementation on muscle contractile properties and nitrate tolerance in postmenopausal women.
Participants: Twenty-two postmenopausal women without overt comorbidities completed the study.
Interventions: Participants were randomized to receive daily 20 grams of nitrate-rich beetroot extract (BET) providing approximately 548 mg (8.8 mmol) nitrate or nitrate-depleted beetroot extract (PLA) with around 43 mg (0.7 mmol) nitrate for a duration of eight weeks.
Endpoints: Primary outcomes included fasting plasma nitrate and nitrite concentrations measured at baseline, week 4, and week 8. Secondary outcomes comprised measures of skeletal muscle contractile properties, focusing on maximal knee extensor torque (F0), maximal power (Pmax), and maximal velocity (Vmax) assessed at various angular velocities.
Key Findings
Circulating Nitrate and Nitrite: After four weeks, the BET group exhibited significantly elevated fasting nitrate levels compared to placebo, with a further significant increase in both nitrate and nitrite concentrations at eight weeks. This sustained elevation indicates continued NO precursor availability without apparent nitrate tolerance.
Muscle Contractile Properties: Maximal knee extensor torque (F0) was significantly greater in the BET group at week 8 compared with placebo (p=0.004), demonstrating enhanced muscle strength. Although maximal power (Pmax) and maximal velocity (Vmax) at a single point did not change significantly, analyses of peak torque and power over various angular velocities revealed improvements at clinically relevant speeds:
- Peak torque improvements at 60°·s⁻¹ and 90°·s⁻¹ angular velocities.
- Enhanced peak power at 90°·s⁻¹, 180°·s⁻¹, and 270°·s⁻¹ angular velocities.
These multidimensional enhancements suggest improved functional muscle performance potentially translating to better physical capacity in daily activities.
Nitrate Tolerance and Safety: There was no evidence of diminished nitrate/nitrite elevation or muscle performance benefit over the eight weeks, arguing against nitrate tolerance development with this regimen. Compliance and adverse events were not detailed but the intervention was well tolerated based on the completion rate.
Expert Commentary
This study provides compelling evidence that sustained dietary nitrate supplementation via beetroot extract enhances NO bioavailability and muscle function in postmenopausal women, a group at high risk of muscle decline. The use of a nitrate-depleted placebo strengthens causative inference by controlling for potential confounders inherent to beetroot’s other bioactive components.
The selective improvement in torque and power at specific angular velocities is physiologically relevant, as these parameters closely relate to functional movements such as walking, stair climbing, and preventing falls. The absence of changes in maximal velocity could indicate that nitrate supplementation preferentially affects force and power-generation pathways rather than contractile speed.
Although the sample size is modest and generalizability may be limited, findings align with the biological plausibility that dietary nitrate augments NO-mediated vascular and muscle energetics, reducing the impact of menopause-associated declines.
Future studies could expand on these results by examining longer supplementation durations, effects on muscle endurance, real-world functional outcomes, and interactions with hormone replacement therapy.
Conclusion
Eight weeks of daily nitrate-rich beetroot extract supplementation significantly raises fasting plasma nitrate and nitrite levels and enhances knee extensor muscle strength and power in postmenopausal women. These data suggest a promising nutritional strategy to mitigate menopause-related muscle function decline, potentially improving physical independence and quality of life. Larger trials with extended follow-up and mechanistic exploration are warranted to confirm these benefits and facilitate clinical translation.
References
Frederico Ramos Junior OJ, Pinheiro VDS, Alvares TS. Eight weeks of nitrate-rich beetroot extract supplementation on fasting nitrate and nitrite levels and skeletal muscle contractile properties in postmenopausal women: Results of a randomized, placebo-controlled, and parallel trial. Free Radic Biol Med. 2025 Oct;238:105-112. doi: 10.1016/j.freeradbiomed.2025.06.026. Epub 2025 Jun 17. PMID: 40553891.
Additional references relevant to nitrate supplementation and muscle function can be consulted but are beyond the scope of this summary.
