Nitrates and Nitrites

Few substances in the food supply are as misunderstood as nitrates and nitrites. They are simple nitrogen-and-oxygen compounds — a nitrate ion is one nitrogen atom bound to three oxygens, a nitrite is one nitrogen bound to two — and they turn up in three very different places: naturally in soil and drinking water, naturally and abundantly in vegetables, and deliberately added to cured and processed meats such as bacon, ham, and hot dogs. Because the same word appears on a bag of arugula, a slice of deli ham, and a well-water test report, people understandably assume it means the same thing everywhere. It does not.

The honest answer to “are nitrates and nitrites good or bad for me?” is that it depends almost entirely on the source and the company the compound keeps. The very same nitrate can help relax your blood vessels and lower blood pressure when it arrives inside a bowl of beets — or it can feed the formation of cancer-linked compounds when it comes from nitrite-cured meat fried at high heat. This page walks through the chemistry in plain terms, the real concern with processed meat, the surprising “vegetable paradox,” the marketing sleight-of-hand behind “uncured” and “celery-powder” labels, the separate question of nitrate in drinking water, and practical guidance that avoids both fear-mongering and false reassurance.

Overview: One Compound, Three Very Different Stories
The Chemistry in Plain Terms
The Processed-Meat Concern, Honestly
The Vegetable Paradox
The “Uncured” and Celery-Powder Label Trick
Nitrate in Drinking Water
Who Should Be Careful
Practical Guidance
The Honest Bottom Line
Research Papers
Connections
Featured Videos

Overview: One Compound, Three Very Different Stories

Nitrate (chemical shorthand NO3) and nitrite (NO2) are part of the natural nitrogen cycle that runs through soil, plants, water, and our own bodies. Plants pull nitrate up from the ground and use it to build proteins, which is why leafy greens and root vegetables are naturally rich in it. The same nitrate leaches into groundwater, especially where fertilizer and manure are used. And for well over a century, people have added nitrate and nitrite salts to meat to preserve it, keep it safe, and give it that familiar pink cured color.

Here is the key idea to carry through the whole page: nitrate and nitrite are not inherently “toxins” or inherently “nutrients.” They are reactive building blocks that can travel down one of two roads in the body. Down one road they become nitric oxide, a beneficial signaling molecule that widens blood vessels. Down the other road, under specific conditions, they help form nitrosamines, a family of compounds several of which are carcinogenic. What tips the balance is context — the food matrix, the cooking method, and what antioxidants happen to be present. That is why the truthful summary is nuanced: mostly beneficial from vegetables, a genuine concern from processed meat, and a real but manageable issue in some drinking water.

The Chemistry in Plain Terms

You do not need a chemistry degree to follow the important part. Think of a short chain of conversions:

Nitrate is relatively inert. On its own, the nitrate ion is fairly stable and unreactive. It mostly matters as a reservoir — a starting material that the body and friendly bacteria can convert into something more active.
Nitrate becomes nitrite. Bacteria on the surface of your tongue, and microbes in the gut, chemically reduce nitrate to nitrite. There is even a clever loop called the enterosalivary circulation: nitrate you swallow is absorbed, concentrated back into your saliva, and reduced to nitrite by oral bacteria before you swallow it again. (This is one reason strong antibacterial mouthwash can blunt some of nitrate’s blood-pressure benefits.)
Nitrite then reaches a fork in the road. This is the crucial step, because nitrite is reactive and its fate depends on the surrounding conditions.

The beneficial road — nitric oxide. In the acidic stomach and in the bloodstream, nitrite can be converted into nitric oxide (NO). Nitric oxide is a tiny but powerful signaling molecule your body also makes on its own; it relaxes the smooth muscle lining your blood vessels, so they widen and blood flows more easily. This is the basis of the well-studied “nitrate–nitrite–nitric oxide pathway,” and it is why dietary nitrate has been shown to modestly lower blood pressure and improve the efficiency of exercising muscle.

The harmful road — nitrosamines. When nitrite meets certain nitrogen-containing compounds called secondary amines — which are plentiful in protein-rich meat — especially under high heat or acidic conditions, it can react to form N-nitroso compounds, better known as nitrosamines. Several nitrosamines (for example NDMA, N-nitrosodimethylamine) are established animal carcinogens and probable human carcinogens. This reaction can happen in the frying pan and can also happen inside the acidic stomach after eating.

So the deciding factor at the fork is simple to state: antioxidants versus amines-plus-heat. Vitamin C and plant polyphenols push nitrite toward helpful nitric oxide and actively block nitrosamine formation. A hot pan full of amine-rich cured meat pushes it the other way. Same starting atom, opposite destinations.

The Processed-Meat Concern, Honestly

Nitrite (usually sodium or potassium nitrite) and nitrate (historically saltpeter, potassium nitrate) are added on purpose to cured and processed meats — bacon, ham, hot dogs, salami, pepperoni, sausages, and sliced deli/luncheon meats. There are real reasons the industry uses them:

Safety. Nitrite strongly inhibits Clostridium botulinum, the bacterium that causes botulism. This is not a trivial benefit — it is a genuine food-safety function that helped make preserved meats safe to store.
Color. Nitrite reacts with the meat pigment myoglobin to fix the stable pink-red color of cured ham and hot dogs (otherwise cured meat would look gray-brown).
Flavor and shelf life. Nitrite contributes the characteristic “cured” taste and slows the fats from going rancid.

The problem is what else is in the package. Meat is rich in the amines nitrite can react with, and processed meats are often cooked at high heat — think of bacon fried until crisp. Both conditions favor nitrosamine formation, and fried bacon in particular is one of the foods where preformed nitrosamines have been measured. Additional nitrosamine can then form in the acidic stomach after the meal.

This is a large part of why, in 2015, the World Health Organization’s International Agency for Research on Cancer (IARC) classified processed meat as a Group 1 carcinogen — its highest category, meaning there is sufficient evidence that it causes cancer in humans, specifically colorectal cancer. (Unprocessed red meat was placed one step down, in Group 2A, “probably carcinogenic.”) The IARC working group estimated that each 50-gram daily portion of processed meat — roughly a couple of slices of bacon or one hot dog — was associated with about an 18% higher relative risk of colorectal cancer. The nitrite-to-nitrosamine pathway is one of the leading mechanisms behind this link, alongside heme iron and the heterocyclic amines produced by high-heat cooking.

Two honest caveats keep this in proportion. First, an IARC Group 1 label describes how strong the evidence is that a substance can cause cancer — it does not mean processed meat is as potent, gram for gram, as tobacco smoke, which sits in the same category. Second, the absolute increase in any one person’s lifetime risk from an occasional hot dog is small. The concern is about regular, habitual consumption across a lifetime and across a population. Enjoying bacon now and then is not a health emergency; eating processed meat every day is a habit worth changing.

The Vegetable Paradox

Here is the fact that surprises almost everyone: for a typical person, the large majority of dietary nitrate — commonly estimated at around 80% — comes not from meat but from vegetables. The richest sources are beets (beetroot), arugula (rocket), spinach, celery, lettuce, radishes, Swiss chard, and rhubarb. A single beet salad can deliver far more nitrate than a slice of ham.

And yet vegetable nitrate is, on the whole, associated with benefit rather than harm. It is the very same nitrate ion that supports the nitric-oxide pathway described above: controlled trials of nitrate-rich beetroot juice and leafy greens have shown modest reductions in blood pressure, improvements in blood-vessel function, and better oxygen efficiency during exercise (the reason beetroot juice became popular with endurance athletes). Population studies of vegetable nitrate generally find neutral-to-favorable associations with cardiovascular health, not the cancer signal seen with processed meat.

Why the opposite outcome from the identical molecule? Because vegetables deliver nitrate packaged with vitamin C, polyphenols, and other antioxidants, and without a high-heat, amine-rich meat matrix. Those antioxidants do two useful things at once: they favor the conversion of nitrite into beneficial nitric oxide, and they actively inhibit the formation of carcinogenic nitrosamines. The nitrate arrives with its own built-in safety escort.

Researchers call this the “nitrate paradox”: the same ion is linked to lower blood pressure when it comes from plants and to cancer risk when it comes from cured meat. The resolution to the paradox is that context is everything — the food matrix, the accompanying antioxidants, and the cooking method decide which road the chemistry takes. The practical upshot is important and reassuring: seeing “nitrate” associated with a vegetable is not a reason to avoid that vegetable. It is arguably a reason to eat it.

The “Uncured” and Celery-Powder Label Trick

Walk down the deli aisle and you will see cured meats labeled “uncured,” “no nitrates or nitrites added,” or the fuller phrase “no nitrates or nitrites added except those naturally occurring in celery powder.” It is easy to read these as “this bacon is the safe kind.” Chemically, that is usually not true.

The trick is botanical. Celery — along with celery powder, celery juice, and celery concentrate — is naturally very high in nitrate. Manufacturers add celery powder together with a bacterial starter culture that converts that natural nitrate into nitrite, which then cures the meat in exactly the same chemical way that manufactured sodium nitrite would. The finished product still contains nitrite; it still forms the same cured color; and it can form the same nitrosamines when fried. Some studies have found that “natural” celery-cured products have nitrite levels that are comparable to, and sometimes more variable or even higher than, conventionally cured meats.

Because of this, U.S. regulators have described the “uncured” and “no nitrate/nitrite added” wording as potentially misleading, and have proposed changing it. For now, treat these phrases as a labeling technicality, not a meaningful health upgrade. Judge the food by what it is — a cured, processed meat — not by the reassuring word on the front of the pack. “Natural” and “organic” cured meats are generally not a nitrite-free or nitrosamine-free choice.

Nitrate in Drinking Water

Drinking-water nitrate is a separate story from food, and it is mostly an agricultural one. Nitrate is highly water-soluble and moves easily through soil, so fertilizer runoff, animal manure, and septic systems can carry it into groundwater and wells — particularly in farming regions. Unlike vegetable nitrate, this nitrate arrives without any accompanying antioxidants, which is part of why it is viewed differently.

The classic, well-established hazard is infant methemoglobinemia, historically called “blue baby syndrome.” In babies under about six months of age, conditions in the immature gut allow bacteria to convert swallowed nitrate into nitrite. That nitrite oxidizes the iron in hemoglobin, turning it into methemoglobin, a form that cannot carry oxygen. The result is a bluish tinge to the skin and, in severe cases, dangerous oxygen deprivation. The textbook scenario is infant formula reconstituted with high-nitrate well water.

Because of this risk, health authorities set limits:

The U.S. Environmental Protection Agency sets a maximum contaminant level of 10 mg/L measured as nitrate-nitrogen (equivalent to roughly 45–50 mg/L expressed as nitrate).
The World Health Organization’s guideline value is 50 mg/L as nitrate, set specifically to protect bottle-fed infants.
Public water systems are routinely tested and treated to meet these limits, so most people on municipal water are already protected.

The gap is private wells, which are generally not regulated or tested by anyone but the owner. If you rely on a private well — especially with an infant in the home, during pregnancy, or if you live near cropland or livestock — you should test the water for nitrate, ideally at least once a year. Two practical points matter here: boiling water does not remove nitrate (it actually concentrates it as water evaporates), and ordinary filters usually do not either — removal requires reverse osmosis, ion exchange, or distillation. Beyond the infant risk, ongoing research is examining possible links between long-term higher nitrate in drinking water and colorectal cancer and certain thyroid and pregnancy outcomes; the evidence is still developing, but it is another reason to keep levels low.

Who Should Be Careful

Most people do not need to worry about nitrate from vegetables at all. Caution is warranted in a few specific situations:

Everyone, with processed meat. Keep cured and processed meats (bacon, ham, hot dogs, salami, deli meats) occasional rather than daily. This is the single most useful takeaway for the general population.
Infants under six months. Do not reconstitute formula with untested or high-nitrate well water. If your supply is a private well, have it tested before using it for a baby.
Pregnant women. Have private well water tested; some studies link higher drinking-water nitrate to adverse pregnancy outcomes, and the developing infant is the most sensitive to methemoglobinemia.
Private-well households, particularly those near farmland, feedlots, or septic systems.
People with certain conditions. Individuals with an inherited tendency toward methemoglobinemia or with G6PD deficiency are more susceptible and should be extra cautious about high-nitrate water.

Note the flip side of this list: for the average healthy adult, nitrate-rich vegetables are beneficial, and there is no good reason to restrict beets, arugula, or leafy greens out of a fear of “nitrates.”

Practical Guidance

You can act on everything above without anxiety or extreme measures. A handful of simple habits captures nearly all the benefit:

Eat plenty of vegetables — including the nitrate-rich ones. Beets, arugula, spinach, and other leafy greens deliver nitrate alongside the antioxidants that make it beneficial. Here the nitrate is a feature, not a flaw.
Go easy on processed and cured meats. Make bacon, ham, hot dogs, salami, and deli meats an occasional treat rather than a daily staple, and keep portions modest.
Pair meals with vitamin C and antioxidants. Citrus, peppers, tomatoes, berries, and vegetables supply vitamin C, which inhibits nitrosamine formation in the stomach. A meat sandwich with tomato and greens is chemistry working in your favor.
Cook cured meats gently. Lower the heat and avoid charring or crisping bacon to a blackened crunch; high-heat cooking is what drives nitrosamine formation. Discard heavily burnt bits.
Do not be reassured by “uncured,” “natural,” or “no nitrate added” labels. Celery-powder curing produces the same nitrite; treat these products like any other processed meat.
Test private well water for nitrate — especially with an infant, during pregnancy, or near agriculture — and remember that boiling will not remove it.
Favor fresh over cured. When you have the choice, a piece of freshly cooked meat is preferable to a processed, nitrite-cured one.

The Honest Bottom Line

Strip away both the scare headlines and the industry reassurance and you are left with a genuinely nuanced truth: love your vegetables, and go easy on processed meat. It is the very same nitrate ion in both — but the company it keeps decides its fate. Surrounded by the vitamin C and polyphenols of a beet or a handful of arugula, it tends to become helpful nitric oxide that supports healthy blood vessels. Surrounded by the amines of cured meat and the high heat of a frying pan, it can help form carcinogenic nitrosamines.

So do not let the word “nitrate” frighten you away from a beet salad, and do not let the words “natural” or “uncured” talk you into a daily bacon habit. Same chemistry, very different company — and the company is what matters.

Research Papers

Bouvard V, Loomis D, Guyton KZ, et al. Carcinogenicity of consumption of red and processed meat. Lancet Oncol. 2015;16(16):1599–1600. doi:10.1016/S1470-2045(15)00444-1 — the IARC Working Group summary classifying processed meat as a Group 1 carcinogen for colorectal cancer.
Santarelli RL, Pierre F, Corpet DE. Processed meat and colorectal cancer: a review of epidemiologic and experimental evidence. Nutr Cancer. 2008;60(2):131–144. doi:10.1080/01635580701684872 — reviews the nitrite/nitrosamine, heme-iron, and high-heat pathways linking processed meat to colorectal cancer.
Lundberg JO, Weitzberg E, Gladwin MT. The nitrate–nitrite–nitric oxide pathway in physiology and therapeutics. Nat Rev Drug Discov. 2008;7(2):156–167. doi:10.1038/nrd2466 — foundational review of how dietary nitrate is recycled into nitrite and nitric oxide.
Bryan NS, Ivy JL. Inorganic nitrite and nitrate: evidence to support consideration as dietary nutrients. Nutr Res. 2015;35(8):643–654. doi:10.1016/j.nutres.2015.06.001 — argues that nitrate and nitrite from vegetables act as beneficial dietary nutrients.
Hord NG, Tang Y, Bryan NS. Food sources of nitrates and nitrites: the physiologic context for potential health benefits. Am J Clin Nutr. 2009;90(1):1–10. doi:10.3945/ajcn.2008.27131 — shows most dietary nitrate comes from vegetables and frames the “nitrate paradox.”
Webb AJ, Patel N, Loukogeorgakis S, et al. Acute blood pressure lowering, vasoprotective, and antiplatelet properties of dietary nitrate via bioconversion to nitrite. Hypertension. 2008;51(3):784–790. doi:10.1161/HYPERTENSIONAHA.107.103523 — the classic beetroot-juice trial showing blood-pressure reduction.
Kapil V, Khambata RS, Robertson A, et al. Dietary nitrate provides sustained blood pressure lowering in hypertensive patients: a randomized, phase 2, double-blind, placebo-controlled study. Hypertension. 2015;65(2):320–327. doi:10.1161/HYPERTENSIONAHA.114.04675 — sustained blood-pressure lowering from dietary nitrate in people with hypertension.
Larsen FJ, Weitzberg E, Lundberg JO, Ekblom B. Effects of dietary nitrate on oxygen cost during exercise. Acta Physiol (Oxf). 2007;191(1):59–66. doi:10.1111/j.1748-1716.2007.01713.x — nitrate reduces the oxygen cost of exercise, the basis for beetroot use in sport.
Song P, Wu L, Guan W. Dietary nitrates, nitrites, and nitrosamines intake and the risk of gastric cancer: a meta-analysis. Nutrients. 2015;7(12):9872–9895. doi:10.3390/nu7125505 — finds nitrite and nitrosamine intake, but not nitrate, associated with gastric-cancer risk.
Bryan NS, Alexander DD, Coughlin JR, Milkowski AL, Boffetta P. Ingested nitrate and nitrite and stomach cancer risk: an updated review. Food Chem Toxicol. 2012;50(10):3646–3665. doi:10.1016/j.fct.2012.07.062 — a nuanced review concluding nitrate itself is not the villain at typical dietary exposures.
Fewtrell L. Drinking-water nitrate, methemoglobinemia, and global burden of disease: a discussion. Environ Health Perspect. 2004;112(14):1371–1374. doi:10.1289/ehp.7216 — examines the “blue baby” infant methemoglobinemia risk from drinking-water nitrate.
Ward MH, Jones RR, Brender JD, et al. Drinking water nitrate and human health: an updated review. Int J Environ Res Public Health. 2018;15(7):1557. doi:10.3390/ijerph15071557 — updated review of drinking-water nitrate and cancer, thyroid, and pregnancy outcomes.