L-Citrulline
The amino acid that replaced arginine in pre-workouts, for the good reason that arginine never survived digestion.
6-8 g citrulline malate, or 3-6 g pure L-citrulline
C Mixed or limited evidencePerformance
Performance
Beetroot (Dietary Nitrate)
Also known as: beet juice, dietary nitrate, nitric oxide, beetroot juice
One of the few endurance aids that genuinely works — and it works through a bacterial step in your mouth that mouthwash can abolish.
Grade BGood human evidence
Studied dose6.5-13 mmol nitrate (roughly 400-800 mg), typically one concentrated shot
TimingPeak plasma nitrite is 2-3 hours after …
EvidenceGrade B
CategoryPerformance
Consistent RCT evidence for improved exercise economy and time-to-exhaustion, with the clearest effects in recreational athletes. The benefit shrinks substantially in elite endurance athletes.
Beetroot is the rare supplement whose mechanism has a genuinely strange step in it. Swallow nitrate from beets or leafy greens and roughly a quarter of it is secreted back into your saliva, where bacteria living on the back of your tongue reduce it to nitrite. Swallow that, and in the oxygen-poor conditions of hard-working muscle it converts to nitric oxide. Which means antibacterial mouthwash, used at the wrong moment, can wipe out the effect entirely — a finding that has been replicated and is still the best party fact in sports nutrition.
The payoff is a measurable drop in the oxygen cost of submaximal exercise, on the order of 3-5%. You are, briefly, a slightly more efficient engine. In practice that shows up as longer time-to-exhaustion and better time-trial performance in efforts from about five to thirty minutes.
The important caveat is who benefits. The effect is clearest in recreational and moderately trained athletes and shrinks markedly in elite endurance competitors, whose muscle already runs close to its efficiency ceiling and whose habitual vegetable intake is often high enough to blunt any additional response. If you are a national-level cyclist the honest expectation is very little. If you are a decent club runner it is one of the few legal aids with a real effect size.
Use is simple. Concentrated shots deliver 6-13 mmol of nitrate in 70 ml; whole beetroot juice needs about half a litre. Take it two to three hours pre-event, or better, load daily for three to six days beforehand — multi-day protocols produce more reliable responses than a single dose. Skip the antibacterial mouthwash for the duration, and expect harmless pink urine.
One genuine caution: nitrate supplements interact meaningfully with nitrate-based heart medications and with erectile-dysfunction drugs, both of which work on the same nitric-oxide pathway. The combination can drop blood pressure sharply. That is a conversation with a prescriber, not a thing to experiment with.
How it works
Dietary nitrate is reduced to nitrite by bacteria on the tongue, then to nitric oxide in the low-oxygen environment of working muscle. The resulting vasodilation and improved mitochondrial efficiency lower the oxygen cost of a given workload.
What the evidence supports
- Improves exercise economy (lower O2 cost at a given workload) typically 3-5% in recreational athletesB
- Improves time-trial and time-to-exhaustion performance clearest in efforts of 5-30 minutesB
- Lowers resting blood pressure a few mmHg systolic, sustained with daily intakeB
- Improves performance in elite endurance athletes consistently smaller or absent at the top of the sportD
Safety
Beetroot juice is food, and the nitrate doses used in trials are comparable to a large serving of leafy greens. The dietary-nitrate-and-cancer worry derives from cured-meat nitrite chemistry and does not transfer to vegetable sources, which arrive with the vitamin C and polyphenols that block nitrosamine formation.
Reported side effects
- Beeturia — harmless red or pink urine and stool
- Mild GI upset from concentrated juice
Interactions
- Additive hypotension with nitrate heart medication (nitroglycerin, isosorbide) and PDE5 inhibitors such as sildenafil — do not combine without medical advice.
- Antibacterial mouthwash abolishes the oral bacterial step and with it most of the effect.
This guide is educational, not medical advice. Talk to a physician or pharmacist before starting any supplement, especially alongside prescription medication or a medical condition.
Common questions
- What does Beetroot (Dietary Nitrate) do?
- One of the few endurance aids that genuinely works — and it works through a bacterial step in your mouth that mouthwash can abolish. Its best-supported effects are improves exercise economy (lower O2 cost at a given workload) and improves time-trial and time-to-exhaustion performance.
- Does Beetroot (Dietary Nitrate) actually work?
- Good human evidence (grade B). Consistent RCT evidence for improved exercise economy and time-to-exhaustion, with the clearest effects in recreational athletes. The benefit shrinks substantially in elite endurance athletes.
- How much Beetroot (Dietary Nitrate) should I take?
- The studied range is 6.5-13 mmol nitrate (roughly 400-800 mg), typically one concentrated shot, daily for 3-6 days, or 2-3 hours before an event. Start at the low end — more is not better once the effective range is covered.
- When should I take Beetroot (Dietary Nitrate)?
- Peak plasma nitrite is 2-3 hours after ingestion — time a single dose accordingly. Multi-day loading works better than a one-off for most people.
- Is Beetroot (Dietary Nitrate) safe?
- Beetroot juice is food, and the nitrate doses used in trials are comparable to a large serving of leafy greens. The dietary-nitrate-and-cancer worry derives from cured-meat nitrite chemistry and does not transfer to vegetable sources, which arrive with the vitamin C and polyphenols that block nitrosamine formation. The most reported side effects are beeturia — harmless red or pink urine and stool, mild GI upset from concentrated juice.
- What should you not mix Beetroot (Dietary Nitrate) with?
- Additive hypotension with nitrate heart medication (nitroglycerin, isosorbide) and PDE5 inhibitors such as sildenafil — do not combine without medical advice. Antibacterial mouthwash abolishes the oral bacterial step and with it most of the effect. Ask a pharmacist or physician before combining it with prescription medication.
References
Evidence review last updated