Dietary nitrates from vegetables are converted to nitrite by bacteria on the tongue and then to nitric oxide in the bloodstream and tissues. Nitric oxide is a vasodilator that reduces peripheral vascular resistance, improves mitochondrial efficiency, and enhances oxygen delivery to working muscle. The discovery that vegetable nitrates produce these effects, rather than the synthetic nitrates in processed meat which behave differently, is one of the significant nutritional research findings of the past decade.
The Highest Nitrate Vegetables
- Beetroot and beetroot juice: 250mg nitrate per 250ml juice; the most studied vegetable nitrate source for exercise performance
- Rocket: the highest nitrate content of any common salad green at approximately 480mg per 100g
- Spinach: 250mg nitrate per 100g
- Celery: 200mg per 100g
- Swiss chard and watercress: 150 to 200mg per 100g
What the Research Shows for Exercise
A meta-analysis of 23 randomised controlled trials found that dietary nitrate supplementation from beetroot juice significantly improved time trial performance in recreational and trained athletes. The effect size was 3 percent improvement in endurance performance, which translates to meaningful real-world gains. For older adults, the benefits extend beyond performance: a 2016 study found that nitrate-rich spinach improved cognitive performance alongside physical performance, potentially through improved cerebral blood flow.