Supplements: Dietary Nitrates — Beetroot Juice and Exercise Performance
Beetroot juice at 400–600mg nitrate (70ml concentrate) reduces O2 cost at submaximal exercise by 1–3% and improves time trial performance by ~1–2%. Peak plasma nitrate occurs 2–3 hours post-ingestion. Elite athletes show consistently smaller responses than recreational athletes.
| Measure | Value | Unit | Notes |
|---|---|---|---|
| Evidence Tier | 2 | tier | Tier 2 — consistent mechanistic and performance evidence in recreational/trained athletes; attenuation in elite athletes reduces broad applicability |
| Standard Nitrate Dose | 400–600 | mg NO3− | Per 70ml beetroot juice concentrate shot; standard single dose for acute performance studies |
| O2 Cost Reduction (submaximal) | 1–3 | % | Nitric oxide reduces the O2 cost of producing a given mechanical output — effectively improving exercise efficiency |
| Time Trial Improvement | ~1–2 | % | Across cycling and running time trials in trained recreational athletes; effects are smaller in elite athletes |
| Peak Plasma Nitrate Timing | 2–3 | hours post-ingestion | Peak plasma NO3−/NO2− at approximately 2–3 hours after ingestion; consume 2–3h before exercise |
| Duration of Loading Protocol | 3–7 | days | Chronic loading (daily doses for 3–7 days) may provide greater ergogenic effect than single acute dose |
| Oral Bacteria Requirement | Critical | factor | NO3−→NO2− conversion requires oral bacteria; antibacterial mouthwash before beetroot juice eliminates most of the effect |
The Nitrate Pathway: NO3− → NO2− → NO
Unlike most supplements where the mechanism is direct, dietary nitrate works through a two-step biological conversion pathway that depends critically on gut and oral bacteria:
- Absorption: Inorganic nitrate (NO3−) from food or supplements is absorbed primarily in the small intestine
- Salivary secretion: ~25% of absorbed NO3− is actively secreted into saliva by salivary glands
- Bacterial reduction: Oral bacteria reduce NO3− to nitrite (NO2−) — this step is eliminated by antibacterial mouthwash
- Gastric reduction: Swallowed NO2− is reduced to nitric oxide (NO) in the stomach (especially under acidic conditions)
- Systemic effects: NO causes smooth muscle relaxation (vasodilation), reduces the O2 cost of mitochondrial ATP production, and may improve contractile efficiency
The efficiency of step 3 is highly individual, explaining some of the variation in response to dietary nitrate supplementation.
Performance Response by Population
| Population | Exercise Type | Nitrate Dose | Performance Improvement | Evidence Quality | Notes |
|---|---|---|---|---|---|
| Untrained (<45 mL/kg/min VO2max) | Cycling time trial | 400mg | ~3–5% | Tier 2 | Largest responses seen |
| Recreationally trained (45–55 mL/kg/min) | Running/cycling time trial | 400–600mg | ~1–3% | Tier 1–2 | Majority of published RCTs |
| Well-trained (55–65 mL/kg/min) | Cycling time trial | 400–600mg | ~0.5–2% | Tier 2 | Smaller and more variable response |
| Elite (>65 mL/kg/min) | Time trial | 400–800mg | ~0–1% | Tier 2 | Hoon 2013: no significant effect in elite rowers |
| Older adults (60+) | Submaximal cycling | 400mg | ~3–5% | Tier 2 | Age-related decline in eNOS may increase response |
| Altitude exercise | Cycling power output | 400–600mg | ~2–4% | Tier 2 | Hypoxia enhances NO2−→NO conversion |
Sources: Food vs Supplement
Concentrated beetroot juice shots (70ml) are the most extensively studied form, providing ~400–600mg NO3−. Dietary sources include:
- Rocket/arugula: ~480mg NO3−/100g — most concentrated vegetable source
- Spinach: ~250mg NO3−/100g
- Beetroot (raw): ~250mg NO3−/100g
- Celery: ~200mg NO3−/100g
Notably, food preparation matters: boiling vegetables removes 50–80% of nitrate into the cooking water. Raw or lightly steamed vegetables retain the most nitrate. Sodium nitrate supplements are also available but have less published research than the beetroot juice formulation.
What Doesn’t Work
Nitric oxide “booster” supplements based on L-arginine (the immediate NO precursor) have consistently failed to replicate the performance effects of dietary nitrate in healthy individuals. This is because intestinal first-pass metabolism and limited L-arginine uptake by eNOS in healthy endothelium makes oral L-arginine a poor NO substrate at typical supplement doses. The NO3−→NO pathway bypasses this limitation.
Related Pages
Sources
- Jones AM. (2014). Dietary nitrate supplementation and exercise performance. Sports Med 44(Suppl 1):35–45.
- Hoon MW et al. (2013). The effect of variable doses of inorganic nitrate-rich beetroot juice on simulated 2000m rowing performance in trained athletes. Int J Sports Physiol Perform 9(4):615–620.
- Porcelli S et al. (2016). Aerobic fitness affects the exercise performance responses to nitrate supplementation. Med Sci Sports Exerc 48(8):1577–1585.
Frequently Asked Questions
How does the nitrate-to-nitric oxide pathway work?
Dietary nitrate (NO3−) is absorbed in the small intestine and ~25% is secreted into saliva. Oral bacteria (primarily Veillonella and Actinomyces species) reduce salivary NO3− to nitrite (NO2−). Swallowed NO2− is absorbed and reduced to nitric oxide (NO) in the stomach and bloodstream — a process enhanced by low-oxygen (hypoxic) conditions such as exercising muscle. NO causes vasodilation (increases blood flow), improves mitochondrial efficiency, and reduces the O2 cost of ATP production.
Why do elite athletes respond less to dietary nitrates?
Elite athletes have chronically higher baseline nitric oxide production due to greater training volume, higher cardiac output, and more efficient endothelial NO synthase (eNOS) activity. When baseline NO production is already high, supplemental dietary nitrate has less additional effect — there is a ceiling on vasodilation and mitochondrial efficiency gains. Porcelli et al. (2016) showed the performance response is inversely correlated with VO2max: untrained athletes (~40 mL/kg/min) show the largest benefits; elite athletes (>65 mL/kg/min) show negligible effects.
Can mouthwash ruin the effect of beetroot juice?
Yes. Antibacterial mouthwash (especially chlorhexidine-based products) kills the oral bacteria responsible for NO3−→NO2− conversion. Studies show that using antibacterial mouthwash before or after beetroot juice consumption eliminates 60–90% of the salivary nitrite response and substantially attenuates blood pressure and performance effects. If using beetroot juice for performance, avoid antibacterial mouthwash on the day of supplementation. Standard toothpaste is less disruptive.
Is a single pre-exercise dose sufficient or is loading required?
Acute single doses (400–600mg, 2–3 hours before exercise) show significant performance effects in most studies. Chronic loading (same dose daily for 3–7 days) may produce greater plasma nitrite concentrations and potentially larger performance effects. For single-event competition use, an acute dose is practical. For training phases where nitrate's O2-efficiency benefits are targeted systematically, 3–7 days of loading before a key block is a reasonable protocol. Tolerance does not appear to develop with chronic use the way it does with caffeine.