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Nitrate

Also known as: Beetroot extract, Nitrite, Nitric oxide

Overview

Nitrate (NO3) is a naturally occurring ion found in several plant-based foods, including green leafy vegetables and beets (beetroot). In the human body, dietary nitrate is used to produce nitric oxide, which plays a major role in regulating vascular function. Nitrate supplements are claimed to improve blood pressure, cardiovascular health, and exercise performance.

Benefits

When nitrate (NO3) is ingested, bacteria in the mouth convert most of it to nitrite (NO2). The remaining nitrate is absorbed in the intestine and enters the blood; however, nitrate circulating in the blood can be taken up by the salivary glands to be reduced to nitrite. This means that nitrate taken in a capsule initially bypasses the oral bacteria, but it is eventually taken up by the salivary glands to be reduced to nitrite. Interestingly, the human body lacks the biological enzymes necessary to convert nitrate to nitrite, so humans rely on bacteria in the mouth to complete this conversion. This step is vital because nitrite is then metabolized in the stomach to produce nitric oxide, a molecule that is a major regulator of vascular function. The subsequent rise in plasma nitric oxide increases vasodilation and blood flow, which helps increase the delivery of oxygen and nutrients to tissues. Therefore, the benefits of supplementation with nitrate are likely caused by the subsequent increase in nitric oxide and its ensuing effect on vascular function. Since nitric oxide also directly affects mitochondrial respiration, glucose uptake, and contractile function in skeletal muscle, the effects of supplementation with nitrate on exercise performance are also likely driven by the rise in nitric oxide.

How it works

Observational studies have shown that a higher intake of nitrate from dietary vegetables is associated with a lower risk of cardiovascular disease and of cardiovascular disease mortality. Accordingly, some randomized controlled trials have shown that supplementation with nitrate can improve variables associated with cardiovascular health. For example, supplementation with nitrate (sodium nitrate/potassium nitrate capsules, beetroot juice, or beetroot extract) has been shown to lower blood pressure and increase flow-mediated dilation in large blood vessels (a.k.a. vascular function). However, the effect of nitrate on blood pressure in people with hypertension is variable and needs further research. Furthermore, it has yet to be determined whether nitrate-induced improvements in blood pressure or vascular function contribute to a lowered risk of cardiovascular disease. Supplementation with nitrate or beetroot juice before exercise shows only trivial effects when pooling all types of aerobic exercise performance tests but small to moderate beneficial effects on time to exhaustion at a fixed intensity. Some studies have also found a benefit of nitrate/beetroot juice on sprint performance metrics and power/velocity during resistance-based exercises, suggesting that supplementation with nitrate might improve explosive exercise performance. However, not all studies confirm such findings, and the effects vary between studies. Supplementation with nitrate/beetroot juice might also reduce the oxygen cost of exercise and, therefore, improve running/cycling economy.

Side effects

Formulations: Tablets (sodium/potassium nitrate, beetroot extract) or liquid (beetroot juice). Range of dosages studied: 200 to 1,488 mg (3 to 24 mmol) of nitrate per day. Effective dosage: Blood pressure - Adults: The effective dosage for reducing blood pressure is 744 to 1,488 mg (12 to 24 mmol) of sodium/potassium nitrate in capsules per day or 70 to 250 mL of beetroot juice per day (providing approximately 200 to 800 mg, or 3 to 12 mmol, of nitrate). Vascular function - Adults: The effective dosage for improving vascular function is approximately 200 to 1,000 mg (5 to 16 mmol) of nitrate provided in 70 to 250 mL of beetroot juice. Aerobic exercise performance - Adults: The effective dosage for improving performance during time-to-exhaustion tests is 70 to 500 mL of beetroot juice (providing approximately 250 to 1,000 mg, or 4 to 17 mmol, of nitrate) taken 2 to 3 hours before exercise. Anaerobic exercise performance - Adults: The effective dosage for improving explosive exercise performance is 370 to 1,000 mg (6 to 16 mmol) of nitrate per day provided in beetroot juice (up to 250 mL/day), taken approximately 2 to 3 hours before exercise. Please note that because beetroot juice does not have a standardized nitrate concentration, the nitrate concentration of beetroot juice is variable between manufacturers. In the studies cited on this page, the range of effective dosages studied for beetroot juice is 70 to 500 milliliters per day (providing approximately 200 to 1,000 mg, or 3 to 17 mmol, of nitrate). Other Considerations: The current acceptable daily intake (ADI) — the daily intake over an entire lifetime of a human that appears to be without adverse effects or harm to health — for nitrate is 3.7 mg per kilogram of body weight per day (equivalent to 222 mg/day in a 60 kg person). Nitrate supplements, beetroot extracts, and beetroot juice are not typically taken with food in the studies that have tested their effects. However, their efficacy in the presence vs. the absence of food has not been examined. It is also important to note that nitrate is found naturally in several plant-based foods, including green leafy vegetables and beets (beetroot).

Dosage

Because nitrate can lower blood pressure, taking a nitrate supplement might cause an excessive drop in blood pressure in people who take blood-pressure-lowering medications. Similarly, nitrate may also interact with drugs that cause vasodilation (e.g., drugs used to treat heart failure and erectile dysfunction). Always consult your doctor before taking a nitrate supplement if you use any of these types of medication. Nitrate may pose a health risk to infants and young children, because a high intake can cause methemoglobinemia, a disorder where hemoglobin cannot transport oxygen effectively. High levels of nitrate intake during pregnancy have also been associated with heart defects in newborns. Nitrate in the naturally occurring levels found in vegetables is likely safe for consumption, as is the intake of nitrate at levels typically found in dietary supplements. Furthermore, nitrate-rich vegetables probably have nitrate-induced health benefits. However, due to the increased use of nitrate salts (ammonium nitrate, sodium nitrate, potassium nitrate, calcium nitrate, etc.) in fertilizers, excessive nitrate levels are being found in vegetables and the water supply. High levels of nitrate salts are also used as food additives to manufacture processed meats. This creates an issue, because excessive nitrate intake can increase the levels of N-nitroso compounds (NOCs) in the body. Both high NOC levels and a high dietary nitrate intake have been associated with an increased cancer risk. However, the relationship is complicated.

FAQs

What is nitrate?

Nitrate (NO3) is a naturally occurring ion found in several plant-based foods, including green leafy vegetables and beets (beetroot). However, nitrate salts (nitrate bound to ammonium, sodium, potassium, or calcium) are also used to manufacture processed meats. Additionally, nitrate salts are used in fertilizers which leach into groundwater and, consequently, enter the drinking water supply. Therefore, people ingest nitrate from several sources. Naturally occurring dietary nitrate is often claimed to improve blood pressure and cardiovascular health. Furthermore, nitrate-containing beetroot juice and nitrate-enriched "beetroot extracts" are marketed as dietary supplements claimed to improve blood pressure and sports performance.

What foods contain nitrate?

Nitrate is found in high amounts in green leafy vegetables, beetroot, radish, rhubarb, and more.

What are nitrate’s main benefits?

Does using antiseptic mouthwash prevent the beneficial effects of nitrate?

Some studies have shown that altering the quantity or function of bacteria in the mouth blunts the beneficial effects of dietary nitrate. Such effects have been observed in animal studies of germ-free mice and in clinical studies that have manipulated the oral microbial environment by adding anaerobic bacteria into the mouth or by using antiseptic mouthwash. The typical rise in plasma nitrite after consuming nitrate is also blunted after using antiseptic mouthwash.

Do nitrate-rich foods improve exercise performance?

Because supplementation with nitrate has been shown to improve exercise performance for some types of exercise, it is interesting to explore whether nitrate-rich foods have similar effects. The current evidence shows that beetroot (predominantly administered using beetroot juice) can cause a very small improvement in exercise performance, whereas red spinach, Swiss chard, and rhubarb cannot. However, a limited number of studies have examined this topic, so further research is needed to fully understand the effects of nitrate-rich foods on exercise performance.

Does nitrate improve exercise tolerance and exercise capacity in people with chronic obstructive pulmonary disease (COPD)?

Current evidence shows that nitrate supplementation can lower subjective perceptions of exertion during exercise in people with chronic obstructive pulmonary disease (COPD). Therefore, nitrate might improve exercise tolerance in this population. However, while some trials have found that nitrate/beetroot juice can increase the distance people with COPD can walk, all of the current evidence compiled in systematic reviews and meta-analyses shows large variability in the effect of nitrate on exercise capacity between studies.

Does nitrate improve exercise capacity in people with heart failure?

A systematic review and meta-analysis published in 2020 found that supplementation with nitrate did not increase the length of time people with heart failure could exercise or the distance they could walk. However, currently only three randomized controlled trials have examined this topic, so further research is needed to make conclusions about the effect of nitrate on exercise capacity in people with heart failure.

What factors influence the effect of nitrate on sports performance?

Systematic reviews and meta-analyses have found that supplementation with nitrate tends to work best when taken approximately 2 to 3 hours before exercise. Meta-analyses have also found that the effects of nitrate might be influenced by training status. For example, some meta-analyses have found that effects tend to be diminished in endurance athletes with a high performance level (e.g., elite athletes) and that nitrate tends to work best in recreational athletes or nonathletes during longer-duration time-to-exhaustion tests.