Key takeaways
- L-arginine, L-citrulline and beetroot nitrate all appear in “pump” formulas.
- Much of the arginine you swallow is broken down before it reaches the bloodstream; citrulline is converted into arginine in the body.
- None of these ingredients has an authorised UK health claim, so be wary of big promises on labels.
- Sleep, food, training and hydration matter far more than any pump ingredient.
In this guide
What each ingredient is
L-arginine is an amino acid found in meat, fish, dairy, nuts and pulses. The body uses it to make nitric oxide.
L-citrulline is an amino acid found in watermelon. The body converts it into arginine. Citrulline malate is citrulline bound to malic acid.
Beetroot nitrate comes from beetroot, a naturally rich source of dietary nitrate. It's popular with endurance athletes.
Side-by-side comparison
| L-arginine | L-citrulline | Beetroot nitrate | |
|---|---|---|---|
| Food source | Meat, nuts, pulses | Watermelon | Beetroot, leafy greens |
| How it's used | Partly broken down in the gut and liver | Converted into arginine in the kidneys | A separate nitrate pathway |
| Research | Mixed | Mixed, growing | Mostly endurance studies |
| Authorised UK claim | None | None | None |
Why many formulas use both: combining arginine with citrulline is a common approach, since citrulline provides a slower route to arginine. Research on the combination is still limited.
Reading a pre-workout label
- Check amounts, not just names. “Proprietary blends” can hide tiny doses.
- Check the caffeine. A strong coffee has around 100mg; some pre-workouts have 300mg or more. See our low-caffeine pre-workout guide.
- Look for authorised claims. Vitamins and minerals such as B12 and magnesium have them; pump ingredients don't.
- Tingles usually come from beta-alanine. See beta-alanine tingles.
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Intra-Workout Blend
- 750mg L-citrulline malate, 750mg L-arginine aspartate and 500mg beetroot nitrate
- Just 40mg caffeine per serving
- Vitamin B12, vitamin C and niacin contribute to the reduction of tiredness and fatigue; magnesium contributes to normal muscle function
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Shop the blend →Safety points
Pre-workouts aren't suitable for under-18s, or during pregnancy or breastfeeding. If you have low or high blood pressure, a heart condition, or take blood pressure medicine or nitrates, speak to your GP before using arginine, citrulline or nitrate products. Count caffeine from all sources.
Questions people ask
Is citrulline better than arginine?
Citrulline is often preferred because less of it is broken down before it reaches the bloodstream, but research on both is mixed.
Is citrulline malate the same as L-citrulline?
Citrulline malate is citrulline bound to malic acid, so a given weight contains less citrulline.
Does beetroot juice work like a pre-workout?
Beetroot is a natural source of nitrate and is popular with endurance athletes. It has no authorised UK health claim.
Why does beetroot turn my wee pink?
That's beeturia, a harmless effect of the beetroot pigment in some people.
Can I take a pump product without caffeine?
Yes. Arginine, citrulline and nitrate don't contain caffeine. Check the full label.
Sources: NHS: caffeine and drinks · EFSA: arginine claims opinion · GB NHC register
This article is general information, not medical advice. Food supplements should not replace a varied, balanced diet and healthy lifestyle.
