What is nitrate?
Nitrate (NO3-) is a naturally occurring ion found in several plant-based foods, including green leafy vegetables and beets (beetroot), and will be the focus of this page.[11][12][13] However, nitrate salts (nitrate bound to ammonium, sodium, potassium, or calcium) are also used to manufacture processed meats.[9][16] Additionally, nitrate salts are used in fertilizers,[17] which leach into groundwater and, consequently, enter the drinking water supply.[18][12] Therefore, people ingest nitrate from several sources.
Naturally occurring dietary nitrate is often claimed to improve blood pressure and cardiovascular health.[19][20] Furthermore, nitrate-containing beetroot juice and nitrate-enriched “beetroot extracts” are marketed as dietary supplements claimed to improve blood pressure and sports performance.[21]
What are nitrate’s main benefits?
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.[22][23] 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[24][1][2] and increase flow-mediated dilation in large blood vessels (a.k.a. vascular function).[3][24] However, the effect of nitrate on blood pressure in people with hypertension is variable and needs further research.[25][2][24][26][27][28] 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.[4][29][30][31][32] 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.[5][6][7] However, not all studies confirm such findings, and the effects vary between studies.[5][6][7] Supplementation with nitrate/beetroot juice might also reduce the oxygen cost of exercise and, therefore, improve running/cycling economy.[29]
Although nitrate is converted to nitrite by bacteria in the mouth to allow humans to synthesize nitric oxide from nitrate (see How does nitrate work?),[33][34] consuming nitrate also provides oral bacteria with a source of nitrite, which may play a role in maintaining oral health.[35][36][37]
Does using antiseptic mouthwash prevent the beneficial effects of nitrate?
Do nitrate-rich foods improve exercise performance?
Does nitrate improve exercise tolerance and exercise capacity in people with chronic obstructive pulmonary disease (COPD)?
Does nitrate improve exercise capacity in people with heart failure?
What factors influence the effect of nitrate on sports performance?
What are nitrate’s main drawbacks?
Because nitrate can lower blood pressure (see What are nitrate’s main benefits?), 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).[14][15] 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.[11][38][39] High levels of nitrate intake during pregnancy have also been associated with heart defects in newborns.[40]
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.[18] High levels of nitrate salts are also used as food additives to manufacture processed meats.[16][9] 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.[41][42][43][44][45] However, the relationship is complicated, so please read Does nitrate cause cancer?) for further details.
Studies that have examined the effect of nitrate/beetroot juice on exercise performance have done so when participants are well rested and not fatigued.[4][29][5][6][7] Therefore, it is not currently known whether nitrate/beetroot juice has the same effect on performance when participants are fatigued (i.e., when participants complete a performance test at the end of a tiring exercise bout). It is also important to note that, in general, the evidence underpinning the benefits of nitrate on exercise performance has a risk of bias because the studies have small sample sizes, sometimes lack a control group, and were funded/authored by manufacturers of the supplements/foods containing nitrate.[4][29][5][6][7]
While adverse effects of nitrate intake are uncommon, some people who drink beetroot juice as a source of supplemental nitrate can develop beeturia (temporary beetroot-colored urine), which occurs due to pigments called betacyanins in beetroot.[46] While unusual, beeturia is a harmless (and fun) side effect of consuming beetroot.
How does nitrate work?
When nitrate (NO3-) is ingested, bacteria in the mouth convert most of it to nitrite (NO2-).[33][34][47] 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.[33][34][47] 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.[33][34][47] This step is vital because nitrite is then metabolized in the stomach to produce nitric oxide,[33][34][47] a molecule that is a major regulator of vascular function.[33][34][47] The subsequent rise in plasma nitric oxide increases vasodilation and blood flow, which helps increase the delivery of oxygen and nutrients to tissues.[11][48] Therefore, the benefits of supplementation with nitrate are likely caused by the subsequent increase in nitric oxide and its ensuing effect on vascular function.[33][47] Since nitric oxide also directly affects mitochondrial respiration, glucose uptake, and contractile function in skeletal muscle,[21][47] the effects of supplementation with nitrate on exercise performance are also likely driven by the rise in nitric oxide.
What are other names for Nitrate
- Beetroot extract
- Nitrite (reduced form)
- Nitric oxide (metabolite)
Dosage information
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:
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).[1][2]
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.[3]
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.[4]
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.[5][6][7]
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).[8][9][10]
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).[11][12][13]
Safety information:
Because nitrate can lower blood pressure (see What are nitrate’s main benefits?), nitrate may interact with drugs used to treat high blood pressure (hypertension). If you use blood-pressure-lowering medications, always consult your doctor before taking a nitrate supplement. Because of nitrate’s effect on blood pressure, nitrate may also interact with drugs that cause vasodilation. This includes heart failure medications and drugs used to treat erectile dysfunction.[14][15] Always consult your doctor before taking a nitrate supplement if you use any of these medications.
Frequently asked questions
Nitrate (NO3-) is a naturally occurring ion found in several plant-based foods, including green leafy vegetables and beets (beetroot), and will be the focus of this page.[11][12][13] However, nitrate salts (nitrate bound to ammonium, sodium, potassium, or calcium) are also used to manufacture processed meats.[9][16] Additionally, nitrate salts are used in fertilizers,[17] which leach into groundwater and, consequently, enter the drinking water supply.[18][12] Therefore, people ingest nitrate from several sources.
Naturally occurring dietary nitrate is often claimed to improve blood pressure and cardiovascular health.[19][20] Furthermore, nitrate-containing beetroot juice and nitrate-enriched “beetroot extracts” are marketed as dietary supplements claimed to improve blood pressure and sports performance.[21]
Nitrate is found in high amounts in green leafy vegetables, beetroot, radish, rhubarb, and more.[11][12][13] See the table below for more information.
| NITRATE-RICH VEGETABLES | Nitrates (mg) | Total oxalate (mg) | Soluble oxalate (mg) | Vitamin K~1~ (μg) |
|---|---|---|---|---|
| Arugula/rocket | 362.4 | 7.1 | <0.5 | 108.6 |
| Turnip greens | 346.7 | 50 | — | 251 |
| Dill | 259 | 159 | 60 | 0 |
| Collard greens | 254.5 | 450 | — | 437.1 |
| Spinach | 248.5 | 656 | 542.6 | 482.9 |
| Swiss chard | 236.3 | 964 | 207.7 | 830 |
| Turnips | 217.4 | 210 | — | 0.1 |
| Rhubarb | 199.9 | 805 | 223 | 29.3 |
| Beetroot | 199.2 | 121 | 74.9 | 0.2 |
| Celery | 196.4 | 17.5 | <0.5 | 29.3 |
| Mustard greens | 187.5 | 128.7 | — | 257.5 |
| Radish | 177.3 | 9.2 | <0.5 | 1.3 |
| Lettuce | 168.9 | 13.6 | <0.5 | 126.3 |
| Watercress | 164 | 10 | <0.5 | 250 |
| Bok choy | 162 | 2 | — | 45.5 |
| Kale | 137.5 | 20 | — | 704.8 |
| Parsley | 130.47 | 136 | 76 | 1640 |
This table is composed of averages from multiple samples. Farming techniques, transport, storage conditions, and cooking methods can all greatly affect the actual nitrate and oxalate content of food.
References: Jackson et al. Nutr Res Rev. 2017.[49] ● Lidder and Webb. Br J Clin Pharmacol. 2013.[50] ● Griesenbeck et al. Nutr J. 2009.[51] ● Tamme et al. Food Addit Contam. 2006.[52] ● Siener et al. Food Chem. 2006. DOI:10.1016/j.foodchem.2005.05.059 ● Hönow and Hesse. Food Chem. 2002.[53] ● Santamaria et al. J. Sci. Food Agric. 1999.[54] ● Dr. Duke's Phytochemical and Ethnobotanical databases ● FoodData Central
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.[22][23] 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[24][1][2] and increase flow-mediated dilation in large blood vessels (a.k.a. vascular function).[3][24] However, the effect of nitrate on blood pressure in people with hypertension is variable and needs further research.[25][2][24][26][27][28] 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.[4][29][30][31][32] 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.[5][6][7] However, not all studies confirm such findings, and the effects vary between studies.[5][6][7] Supplementation with nitrate/beetroot juice might also reduce the oxygen cost of exercise and, therefore, improve running/cycling economy.[29]
Although nitrate is converted to nitrite by bacteria in the mouth to allow humans to synthesize nitric oxide from nitrate (see How does nitrate work?),[33][34] consuming nitrate also provides oral bacteria with a source of nitrite, which may play a role in maintaining oral health.[35][36][37]
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[55] and in clinical studies that have manipulated the oral microbial environment by adding anaerobic bacteria into the mouth[56] or by using antiseptic mouthwash.[57][58][59][58][60] The typical rise in plasma nitrite after consuming nitrate is also blunted after using antiseptic mouthwash.[61][58]
Interestingly, one epidemiological study that examined 945 individuals over 3 years found that frequent mouthwash users (at least twice daily) had a 55% greater risk of developing prediabetes or type 2 diabetes compared to less frequent users and a 49% greater risk compared to nonusers.[62] While this study did not examine mechanisms, the disruption of the nitrate-to-nitrite conversion pathway in the mouth, which is catalyzed by oral bacteria,[33] was discussed as one possible explanation for the findings.
Because supplementation with nitrate has been shown to improve exercise performance for some types of exercise (see What are nitrate’s main benefits?), 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.[63] 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 (and indeed on other outcomes like blood pressure and vascular function).
Current evidence shows that nitrate supplementation can lower subjective perceptions of exertion during exercise in people with chronic obstructive pulmonary disease (COPD).[64] 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,[65][66][67] 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.[68][64][69] Consequently, while there is potential for nitrate supplementation to improve exercise capacity in people with COPD, further high-quality randomized controlled trials are needed to fully understand its efficacy.[68][64][69]
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.[70] However, currently only three randomized controlled trials have examined this topic,[70] so further research is needed to make conclusions about the effect of nitrate on exercise capacity in people with heart failure.
Systematic reviews and meta-analyses have found that supplementation with nitrate tends to work best when taken approximately 2 to 3 hours before exercise.[30] 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 (i.e., tests measuring how long a person can run/cycle at a low to moderate intensity).[29][31][32] That said, some analyses have shown nitrate to work best during shorter exercise bouts (lasting between 2 and 10 min).[30] Nitrate might also be more effective in men than women; however, very few studies in women have been published, so more research is needed to understand whether a sex difference exists.[31][32][30]
The major problem with such analyses is that very few randomized controlled trials have been specifically designed to examine dose-response effects, time course effects, sex differences, etc. Plus, the existing studies include a small number of participants. Further high-quality research is needed to understand when and in whom nitrate works best.
Because nitrate can lower blood pressure (see What are nitrate’s main benefits?), 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).[14][15] 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.[11][38][39] High levels of nitrate intake during pregnancy have also been associated with heart defects in newborns.[40]
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.[18] High levels of nitrate salts are also used as food additives to manufacture processed meats.[16][9] 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.[41][42][43][44][45] However, the relationship is complicated, so please read Does nitrate cause cancer?) for further details.
Studies that have examined the effect of nitrate/beetroot juice on exercise performance have done so when participants are well rested and not fatigued.[4][29][5][6][7] Therefore, it is not currently known whether nitrate/beetroot juice has the same effect on performance when participants are fatigued (i.e., when participants complete a performance test at the end of a tiring exercise bout). It is also important to note that, in general, the evidence underpinning the benefits of nitrate on exercise performance has a risk of bias because the studies have small sample sizes, sometimes lack a control group, and were funded/authored by manufacturers of the supplements/foods containing nitrate.[4][29][5][6][7]
While adverse effects of nitrate intake are uncommon, some people who drink beetroot juice as a source of supplemental nitrate can develop beeturia (temporary beetroot-colored urine), which occurs due to pigments called betacyanins in beetroot.[46] While unusual, beeturia is a harmless (and fun) side effect of consuming beetroot.
The International Agency for Research on Cancer (IARC) has classified ingested nitrate as “probably carcinogenic to humans” (a Group 2A carcinogen).[8][45] This means that “there is limited evidence of carcinogenicity in humans and either sufficient evidence of carcinogenicity in experimental animals or strong mechanistic evidence” from cell-culture experiments (in vitro studies).[71] In humans, this evidence comes from epidemiological observational studies that have shown that higher dietary intakes of nitrate are associated with an increased risk of some types of cancer.[41][42][43][44] Further human evidence is derived from studies that show that drinking tap water that contains high levels of nitrate is associated with several conditions, including colorectal cancer.[72] Similarly, an excessive nitrate intake from processed foods has also been associated with an increased risk of conditions, including gastrointestinal cancer.[11] However, the strength of the association between nitrate intake and cancer risk is variable between the studies, and some studies show that a greater nitrate intake is associated with a lower risk. Consequently, it is unclear whether consuming nitrate directly causes cancer in humans.
The associations between nitrate intake and cancer risk might be explained by the formation of N-nitroso compounds (NOCs) caused by nitrate. This is important because, like nitrate, several N-nitroso compounds have also been classified as “possibly carcinogenic to humans”.[45] Interestingly, drinking water containing nitrate can lead to increased levels of NOCs,[73][74] and high levels of red meat ingestion are also associated with higher levels of NOCs in the body.[73][75][76][77] One clinical study has even shown that drinking beetroot juice can cause a small increase in the formation of NOCs.[78]
The above-described information indicates that ingesting nitrate has the potential to cause cancer. It even suggests that drinking beetroot juice in excessive amounts might pose a health risk due to the possible formation of NOCs. However, there is no known association between drinking beetroot juice and cancer risk.[79] Additionally, nitrate intake through plant-based food sources (green leafy vegetables, beetroot, etc.) has never been found to be associated with health risks. Furthermore, nitrate-containing vegetables (including beetroot) also contain many other nutrients — vitamins and phytochemicals — that function as antioxidants and can inhibit the conversion of nitrate into NOCs.[8] Therefore, the cancer risk from drinking beetroot juice or eating nitrate-containing vegetables is likely to be very low. Furthermore, it is generally agreed that consuming a variety of fruits and vegetables can protect against chronic conditions, including cancer.[80][81]
To summarize, while consuming nitrates in excessive levels may increase the risk of cancer, it is currently believed that nitrate is unlikely to pose a major risk in the amounts people typically consume. However, if people want to reduce their exposure to any potential hazard posed by nitrate, they can choose to refrain from eating processed meats and from drinking tap water in nitrate-contaminated areas.
When nitrate (NO3-) is ingested, bacteria in the mouth convert most of it to nitrite (NO2-).[33][34][47] 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.[33][34][47] 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.[33][34][47] This step is vital because nitrite is then metabolized in the stomach to produce nitric oxide,[33][34][47] a molecule that is a major regulator of vascular function.[33][34][47] The subsequent rise in plasma nitric oxide increases vasodilation and blood flow, which helps increase the delivery of oxygen and nutrients to tissues.[11][48] Therefore, the benefits of supplementation with nitrate are likely caused by the subsequent increase in nitric oxide and its ensuing effect on vascular function.[33][47] Since nitric oxide also directly affects mitochondrial respiration, glucose uptake, and contractile function in skeletal muscle,[21][47] the effects of supplementation with nitrate on exercise performance are also likely driven by the rise in nitric oxide.
Although the food products that contain nitrates differ widely, the nitrates present in processed meats and vegetables are chemically identical.
From an epidemiological perspective, nitrates are commonly thought to be adverse to health due to a long-standing restriction on how much nitrate can be in drinking water (50mg/L) or ground water (due to accumulating in vegetables) due to the risk of infantile methemoglobinemia (baby blue syndrome)[82][83] which does appear to apply to vegetables.[84][85] More commonly, the association between processed meat products that are pink in color (which very commonly use sodium nitrate as a preservative) and cancer occurrence also paints nitrates in the same negative light.[86] Conversely, vegetables are commonly stated to not be associated with cancer risk (which then raises concern about whether or not they are the same molecules).
Both consumption of vegetables (most commonly researched is beetroot[87]) and consumption of the sodium nitrate preservative cause increases in serum nitrate and nitrite, and are considered bioequivalent. In some studies that assess nitrate's bioactivity, liquid solutions of sodium nitrate are even used.[88][89][88]
There are still differences between eating processed meat and vegetables in this regard (intake of sodium through the preservative sodium nitrate and higher intake of potassium via vegetables; less conversion of nitrate into nitrosamines with coingested antioxidants) but the molecule itself is the same.
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