Red spinach extract
Summary
Red spinach extract is a dried leaf extract of Amaranthus dubius that supplies dietary nitrate, about 90 mg per gram. It reliably raises blood nitrate. In small crossover trials of 10 to 16 people, effects on exercise were mixed: one test improved ventilatory threshold and bar speed, while bench-press endurance, offseason training gains and blood pressure did not change.
Key facts
How it works
ProposedInorganic nitrate from the extract is converted by mouth bacteria to nitrite and then to nitric oxide, which relaxes blood vessels and may make muscle use oxygen more efficiently. The trials confirmed higher blood nitrate after dosing; the downstream nitric oxide effects on muscle are proposed, not shown, for this extract.[1][2][6]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Training adaptations | Grade D | No effect | RCT · n = 16 · 2022 | 1 row |
| Endurance | Grade D | Mixed | Crossover RCT · n = 15 · 2017 | 1 row |
| Blood flow | Grade D | Mixed | Crossover RCT · n = 15 · 2016 | 1 row |
| Strength | Grade D | Mixed | Crossover RCT · n = 14 · 2025 | 2 rows |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Strength, power, body composition and blood pressure after 11 weeks of training | No effect | Grade D | RCT · n = 16 · 2022 Division I male baseball players (USA) Form: Red spinach extract, 2 g (180 mg nitrate) · Dose: 2 g/day · Duration: 11 weeks No group-by-time differences for bench-press 1RM, Wingate power, fat-free mass, muscle thickness, resting heart rate or blood pressure; a non-significant trend for peak Wingate power (p=0.095). | 33754923 (opens PubMed)Source [4] |
| Oxygen uptake at ventilatory threshold during a graded exercise test | Mixed | Grade D | Crossover RCT · n = 15 · 2017 Recreationally active young adults (USA) Form: Red spinach extract, single 1,000 mg dose (about 90 mg nitrate) · Dose: 1,000 mg once, about 70 minutes before testing · Duration: Single dose Oxygen uptake at the ventilatory threshold was 6.1% higher than placebo, but time to exhaustion and peak oxygen uptake did not improve (both slightly lower, not significant). | 29910440 (opens PubMed)Source [1] |
| Leg and arm blood-flow responses and blood pressure 1 hour after a dose | Mixed | Grade D | Crossover RCT · n = 15 · 2016 Healthy young adults (8 men, 7 women; USA) Form: Red spinach extract, 1,000 mg (about 90 mg nitrate) · Dose: 1,000 mg once · Duration: Single dose Peak calf blood flow after cuff release rose 13.7% (it fell 14.0% after placebo), but brachial artery flow-mediated dilation, blood pressure and heart rate did not change. | 27695978 (opens PubMed)Source [2] |
| Bench-press velocity, repetitions to exhaustion and perceived exertion | Mixed | Grade D | Crossover RCT · n = 14 · 2025 Resistance-trained men (USA) Form: Red spinach powder (VitaSpinach), dose providing 400 mg nitrate · Dose: Single dose providing 400 mg nitrate, 2 hours before exercise · Duration: Single dose Bar velocity rose (p=0.035) and perceived exertion fell, but total repetitions to exhaustion did not change (p=0.935). | 41441447 (opens PubMed)Source [5] |
| Bench-press repetitions, power, muscle oxygenation and Stroop test | No effect | Grade D | Crossover RCT · n = 10 · 2021 Resistance-trained men (USA) Form: Red spinach extract, 2 g (180 mg nitrate) · Dose: 2 g/day · Duration: 7 days (8th dose 40 minutes before testing) No difference from placebo in repetitions (p=0.549), peak or mean power, muscle oxygenation, Stroop performance or perceived performance. | 34071862 (opens PubMed)Source [3] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Red spinach extract (standardised powder or capsules) | Varies[1][3][4][5] | A single 2 g dose raised plasma and saliva nitrate and nitrite above placebo for at least 8 hours in 16 healthy adults; a 1 g dose raised plasma nitrate about 255–450% within roughly an hour.[6][1][2] | No adverse events were reported in the cited trials; a 2025 systematic review of four spinach-extract trials found no complications.[7][4] | Exercise performance and blood-flow trials (1–2 g/day, or a dose giving 400 mg nitrate) |
Studied doses
Doses studied in human trials ranged from 1,000 mg as a single dose (about 90 mg nitrate) to 2,000 mg/day (180 mg nitrate) for 7 days or 11 weeks. One 2025 trial gave a single dose of red spinach powder providing 400 mg nitrate.[1][3][4][5]
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
None found in our sources.
Who should be careful
- Blood-pressure and nitrate medicines
- No interaction studies exist. The extract is taken to raise nitric oxide, the pathway that nitrate angina drugs and PDE5 inhibitors (such as sildenafil) also act on. A 1 g dose did not change blood pressure in 15 healthy adults, but people on these medicines were not studied.[2][1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
How to read the label
- Check the nitrate, not just the gramsTrials dosed by nitrate: about 90 mg per gram of extract. A label that lists only milligrams of extract does not tell you how much nitrate you get.[1][3]
- Single dose vs daily useThe only positive performance findings came from single doses taken 1–2 hours before testing; 7 days and 11 weeks of daily use showed no benefit.[1][3][4][5]
Cost per studied dose, without the sales pitch
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Cost per studied dose
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Frequently asked questions
Is red spinach the same as regular spinach?
No. Red spinach is an amaranth (Amaranthus dubius), not true spinach (Spinacia oleracea). Supplements use a leaf extract standardised for nitrate.[1]
Does red spinach extract improve workouts?
The evidence is weak and mixed. Single doses improved ventilatory threshold in 15 people and bar speed in 14, but 7 days of use did not change bench-press performance and 11 weeks did not improve training gains.[1][3][4][5]
Does it lower blood pressure?
Not in the trials so far. A single 1 g dose did not change blood pressure in 15 healthy adults, and 11 weeks of 2 g/day did not change it in 16 athletes.[2][4]
How does it compare with beetroot?
Both supply inorganic nitrate. Red spinach extract is a concentrated powder (about 90 mg nitrate per gram); no trial has compared the two head to head.[1]
Sources
- [1]Red Spinach Extract Increases Ventilatory Threshold during Graded Exercise Testing.. Sports (Basel), 2017. crossover-RCT
- [2]Differential vascular reactivity responses acutely following ingestion of a nitrate rich red spinach extract.. Eur J Appl Physiol, 2016. crossover-RCT
- [3]Impact of Red Spinach Extract Supplementation on Bench Press Performance, Muscle Oxygenation, and Cognitive Function in Resistance-Trained Males.. Sports (Basel), 2021. crossover-RCT
- [4]Influence of Dietary Nitrate Supplementation on Physical Performance and Body Composition Following Offseason Training in Division I Athletes.. J Diet Suppl, 2022. RCT
- [5]Effects of Acute Red Spinach Powder (VitaSpinach(®)) Ingestion on Muscular Endurance and Resistance Exercise Performance.. Muscles, 2025. crossover-RCT
- [6]Pharmacokinetic study of amaranth extract in healthy humans: A randomized trial.. Nutrition, 2016. PK-study
- [7]Improved Effect of Spinach Extract on Physical Performance: A Systematic Review of Randomized Controlled Trials.. Cureus, 2025. systematic-review
What changed
- Independent adversarial review: all 7 PMIDs re-verified; evidence figures match abstracts. Clarified the nitrate/PDE5-inhibitor caution and the maker funding of the 2017 study (confirmed in the full text).
- Adversarial second pass: every PMID re-checked against NCBI esummary (title, year, no retraction, erratum or expression-of-concern flags) and every number in each evidence row re-read against its PubMed abstract (PMC full text where the abstract lacked dose or duration). Countries and funding notes kept only where the abstract or full text states them; interactions listed only where a source supports them, otherwise stated as unstudied.
- First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for the cited rows.