Spinach and other leafy greens high in nitrates

Spinach and other leafy greens are high in nitrates.

An athlete seeking an edge over the competition might want to consider a diet high in nitrates. Those simply seeking better exercise performance or better cardiovascular health might also want to consider a high nitrate diet.

In this article we will discuss why and how high-nitrate foods increase athletic performance and cardiovascular health. We will also give you a ranking list of high-nitrate foods

Why are nitrates so special?

Exercise demands that our blood deliver glucose, oxygen and other nutrients to muscle cells. Then the blood must remove the byproducts of energy production from the muscle cells.

During strenuous exercise, our blood vessels can expand and contract to increase blood flow to muscle cells. The better our blood vessels can expand, the more blood can get to muscles. This means more oxygen, glucose and other nutrients get delivered when our blood vessels are more supple and flexible. So they can expand wider.

Think of it like crimping a water hose. A crimped water hose will slow water flow through the hose. But a fully open and flexible hose will allow more water to flow through it.

The ability of blood vessels to expand takes place through a process called the nitric oxide synthase dependent pathway. This pathway is driven by the availability of nitrates – which form nitric oxide.

A number of studies have confirmed that supplementing with nitrates can seriously increase exercise capacity. Research has illustrated that nitrate supplements such as beetroot juice decrease blood pressure and increase blood flow to the muscles.

This means that nitrate supplements like beetroot taken a few hours or days before exercise can increase exercise performance. A 2015 study of 18 adults from the University of Sidney confirmed this. Four days of beetroot supplementation reduced muscle fatigue and exhaustion among the subjects.

But what about a longer-term strategy? Will regularly consuming nitrate-rich foods increase exercise performance on a more permanent basis?

Nitrate diet increases strength, stamina and other factors

Research from Italy’s National Research Council and the Catholic University of the Sacred Heart studied the effect of such a diet. The researchers tested 7 athletes active in basketball, badminton and soccer. Their current diets were tested for a week. Then they were given a list of foods to eat for the next six days. The athletes then went back to their normal diets for 20 days. After that, they ate a high-nitrate diet for six days.

The athletes were told that both diets were good for exercise performance. They were also instructed not to use mouthwash or chewing gum. See section below on this.

On the fifth and sixth days of each diet, the researchers tested the athletic performance of the athletes. In addition to their normal training, the researchers had the athletes do cycling tests, isometric knee extensions and repeated cycling sprinting tests. During the training regimen, the scientists measured breathing capacity, heart rate, blood lactate, muscle force tests, power and resistance tests, and various blood tests. These of course measured plasma blood levels of nitric oxide.

The researchers found the high-nitrate diet significantly increased oxygen uptake among the athletes. It also resulted in lower heart rates for the same exercise output. Pulmonary ventilation and carbon dioxide output levels were also lower. And blood lactate levels were lower among the athletes after six days of the high-nitrate diet.

The high-nitrate diet also resulted in greater muscle contraction and higher torque in the isometric exercises.

The high-nitrate diet also increased the athletes’ peak power output during the sprint testing compared to the control diet.

What foods were in the high-nitrate diet?

The high-nitrate diet included these foods each day:

• Raw spinach – 40 grams a day
• Cooked collard greens – 80 grams a day
• Banana – 130 grams a day
• Pomegranate juice – half a liter per day

What about other nitrate-rich foods?

Certainly, this diet didn’t contain one of the foods most known for nitrate levels: Beetroot. It is likely the reason was not to tip-off the athletes, as the diet with the beets would likely be known as the exercise-boosting diet.

There are, in fact, many other foods that are high in nitrates other than beetroot. And there are many that have more nitrates than beetroot.

The European Food Safety Authority accumulated a number of laboratory analyses in 2008. Here is a list of higher-nitrate foods coming from that and other research, in order of nitrate content (in milligrams per 100 grams):

Top 40 Nitrate Foods

1. Arugula lettuce (480 mg/100g)
2. Amaranth greens (266 mg/100g)
3. Corn salad (Valerianella locusta) (266 mg/100g)
4. Rhubarb (281 mg/100g)
5. Coriander/Cilantro (247 mg/100g)
6. Butter lettuce (198 mg/100g)
7. Mixed lettuce (188 mg/100g)
8. Basil (182 mg/100g)
9. Beet leaf (177 mg/100g)
10. Curly Green leaf lettuce (162 mg/100g)
11. Oakleaf lettuce (155 mg/100g)
12. Borage (153 mg/100g)
13. Chard (151 mg/100g)
14. Endive lettuce (147 mg/100g)
15. White radish (126 mg/100g)
16. Black radish (124 mg/100g)
17. Dill (112 mg/100g)
18. Mustard greens (116 mg/100g)*
19. Beetroot (110-250+ mg/100g)*
20. Romaine lettuce (110 mg/100g)
21. Red Radish (73 mg/100g)
22. Iceberg lettuce (84 mg/100g)
23. Spinach (78-741 mg/100g)*
24. Fennel (78 mg/100g)
25. Celery (69-250+ mg/100g)*
26. String beans (61 mg/100g)
27. Parsley (48 mg/100g)
28. Broccoli (39 mg/100g)*
29. Tomato (39 mg/100g)*
30. Green beans (32 mg/100g)
31. Turnip (31 mg/100g)
32. Chives (30 mg/100g)
33. Escarole lettuce (30 mg/100g)
34. Carrot juice (27 mg/100g)*
35. Vegetable juice (26 mg/100g)*
36. Leeks (26 mg/100g)
37. Dandelion (20 mg/100g)
38. Vegetable soup (21 mg/100g)*
39. Pomegranate juice (13 mg/100g)
40. Carrot (12 mg/100g)

*Note that a 2009 study from the University of Texas measured spinach with a average content of 741 mg/100 grams. Other foods marked with * indicate this same study. This study also gave carrot a 143 mg/100g average and indicated beetroot and celery with more than 250 mg/100g.

In other words, for those who buy U.S.-grown spinach, this food may well be the highest source of nitrates compared to other foods.

high nitrate diet boosts exercise

High nitrate feta salad with spinach, beets and assorted lettuce.

The European Food Safety study is likely more reliable for most growing regions, since the data was accumulated from a number of tests. That said, growing conditions and fertilizer levels can significantly affect nitrate levels in the foods grown there. Spinach, lettuces and beets grown in the U.S. may well have higher nitrate levels due to greater nitrate-based fertilizers used.

Nonetheless, this food chart gives you a recipe-builder for designing meals around high nitrates. From this research we also find the surprising fact that beetroot isn’t the best source of nitrate. The reason why beetroot has been used by many studies is because it is quite convenient to drink beet juice, and it can be concentrated.

We can add to this that red beet juice is quite tasty.

Oral probiotics assist nitric oxide pathway

Mouthwash or chewing gum decrease oral probiotic bacteria counts. Oral probiotics were found to assist in the process of converting nitrate foods to beneficial nitric oxide.

Researchers from Sweden’s Karolinska Institute tested seven adult subjects in a 2008 study. The subjects each took nitrate supplements on separate occasions. Prior to some, they used antibacterial mouthwash. They also took the nitrate supplement without either.

The researchers found when the subjects used mouthwash before nitrate supplementation, their blood nitrite levels did not increase. But when they didn’t use the mouthwash, their blood nitrite levels jumped after the nitrate supplementation.

They concluded:

“We conclude that the acute increase in plasma nitrite seen after a nitrate load is critically dependent on nitrate reduction in the oral cavity by commensal bacteria. The removal of these bacteria with an antibacterial mouthwash will very likely attenuate the NO-dependent biological effects of dietary nitrate.”

The term “commensal bacteria” refers to our oral probiotics.

There may also be health affects to some of these mouthwashes.

In 2016, Duke University researchers tested 12 healthy men using different types of mouthwash. They gave the men 40 milliliters of beet juice and 15 minutes later they gargled with water, a commercial mouthwash (Listerine®), or an antibacterial mouthwash including one with chlorhexidine.

The researchers found a difference in their blood pressure levels after the water and the commercial mouthwash, and the antibacterial mouthwashes. The antibacterial mouthwashes affected blood pressure significantly more.

We can conclude from this research that the beneficial effects of nitrate foods can be muted if our oral bacteria are not healthy.

oral probiotics

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REFERENCES:

Porcelli S, Pugliese L, Rejc E, Pavei G, Bonato M, Montorsi M, La Torre A, Rasica L, Marzorati M. Effects of a Short-Term High-Nitrate Diet on Exercise Performance. Nutrients. 2016 Aug 31;8(9). pii: E534. doi: 10.3390/nu8090534.

Kapil V, Weitzberg E, Lundberg JO, Ahluwalia A. Clinical evidence demonstrating the utility of inorganic nitrate in cardiovascular health. Nitric Oxide. 2014 Apr 30;38:45-57. doi: 10.1016/j.niox.2014.03.162.

European Food Safety Authority (EFSA). Nitrate in vegetables – Scientific Opinion of the Panel on Contaminants in the Food chain. 5 June 2008. DOI: 10.2903/j.efsa.2008.689

Hoon MW, Fornusek C, Chapman PG, Johnson NA. The effect of nitrate supplementation on muscle contraction in healthy adults. Eur J Sport Sci. 2015;15(8):712-9. doi: 10.1080/17461391.2015.1053418.

Hord NG, Tang Y, Bryan NS. Food sources of nitrates and nitrites: the physiologic context for potential health benefits. Am J Clin Nutr. 2009 Jul;90(1):1-10. doi: 10.3945/ajcn.2008.27131.

Govoni M, Jansson EA, Weitzberg E, Lundberg JO. The increase in plasma nitrite after a dietary nitrate load is markedly attenuated by an antibacterial mouthwash. Nitric Oxide. 2008 Dec;19(4):333-7. doi: 10.1016/j.niox.2008.08.003.

Woessner M, Smoliga JM, Tarzia B, Stabler T, Van Bruggen M, Allen JD. A stepwise reduction in plasma and salivary nitrite with increasing strengths of mouthwash following a dietary nitrate load. Nitric Oxide. 2016 Apr 1;54:1-7. doi: 10.1016/j.niox.2016.01.002.