Vegetables are bad for you, scientists say [updated]

s we all know, science is strongly biased toward finding problems. You get no prizes for showing that something is safe. Unfortunately, this causes publication bias that transfers to policies enacted by politicians who don't or can't read the literature.

One chemical that people are concerned about is nitrite (NO−2), which the news media sometimes confuse with nitrate (NO−3). They are chemically different. In the past, it was assumed that nitrites were carcinogenic due to the formation of N-nitrosamines. New scientific research (summarized here) now throws that claim into doubt. But we can't be sure: the field is a wild West.

Vegetables of death

Nitrites are not just found in bacon. Lettuce, tomatoes, and most leafy vegetables are also high in nitrites. Tomatoes were found in a Romanian study to have 0.49 ± 0.17 mg/kg nitrite. Lettuce had 0.79 ± 0.42 mg/kg.^[1] This is lower than bacon, which one study found to have a mean concentration of 10.8 mg/kg.

Lettuce. I couldn't find any arugula anywhere

However, a Danish study got the opposite result. In a paper containing the most badly formatted table known to man,^[2] nitrite in lettuce reached 18 ± 1 mg/kg upon storage, nearly twice as high as bacon. Arugula, which is claimed to be “a nutritional powerhouse with impressive health benefits,” contained 2448 ± 213 mg/kg (226 times higher than bacon), while spinach had 950 ± 58 (88 times more) and parsley came in second with 1207 ± 93 (112 times more than bacon). The levels increased with time of storage, maxing out by 24h. And yes, the authors clearly meant milligrams (mg), not micrograms (μg).

The authors blame nitrate fertilizers under the assumption that nitrate is being converted to nitrite; but of course nitrate is normally in the soil and is essential for growth. When these leafy vegetables were stored frozen at −20°C or −80°C, nitrite was not detected. The authors say this means that storage temperature affects it, but the problem is that freezing lettuce makes it inedible. It's not known whether it's enzymatic activity or bacteria that are doing the dirty deed.

Hot dogs of death

A group of Polish researchers found that hot dogs (which they equated to Polish sausage) contained an average of 60.30 mg/kg nitrites, and suggested that one Polish sausage a day might pose a health risk for young children.^[3]

A meta-analysis,^[4] however, found no significant association between nitrate or nitrite intake and digestive system cancers. In fact, when corrected for factors like sex, region, and fiber intake, nitrite intake had a small protective effect. Elsewhere, scientists are busy creating drugs to increase nitrite release ^[5] because nitrite is metabolized to nitric oxide (NO), an essential signaling molecule.

As with any chemical, the dose makes the poison. There have been 94 cases of people committing suicide by ingesting sodium nitrite.^[6] Autopsies showed nonspecific signs of asphyxia and dark discoloration of the hypostasis (the settled blood after death) and blood. The authors say methemoglobin, a brownish form of hemoglobin in which the heme iron is oxidized, ranged from 6 to 92% of the total hemoglobin.

The LD50 of NaNO₂ is said to be around 71 mg/kg body weight. This means a 150 kg person would have to ingest 10,650 mg of nitrite (the equivalent of 176.6 kg of Polish hot dogs or 4.34 kg of arugula) to have a fifty percent chance of being killed by the nitrite. Arugula costs about $11.21 per kg in the US.

Bacon sandwiches of Death

Most people aren't concerned about overdosing from nitrite. The bigger concern is the possibility of cancer from nitrite metabolites such as N-nitrosamines. There is still controversy about this risk, but unsubstantiated claims from activists will only create skepticism. An example is a group of “leading experts” who recently called for restrictions on bacon.

Pieces of bacon pried from my cold, dead, and slightly greasy hands

The media don't have a link to the supposed study. That's because there isn't one. It's a letter by an NGO called the Coalition Against Nitrites. The WHO classified processed meat as a Group 1 (i.e., human) carcinogen,^[7] the same category as asbestos and tobacco, in 2015. The NGO demands cancer warnings on processed meats and regulations to phase out nitrite. If a good alternative isn't found, that would put bacon on the same trajectory as asbestos, which is banned in “over 60” countries (the exact number depends on the source) with activists, as always, claiming a cover-up. That's a code word meaning they get to sue the company.

The NGO claims that nitrites cause 5400 cases of bowel cancer in the UK, costing £3 billion in the past decade. Their evidence does not back up that claim. Their 'evidence' page (Footnote 1) consists of two observational studies on breast cancer; an article on mania caused by some other chemical cited twice; two articles that don't exist; an opinion article; an old blurb in the UK Guardian; and one fatally flawed paper that used the wrong controls. This shows that their demand has little or no basis in science.

Consumption of processed meat accounts for only 5% of nitrite exposure, with vegetables accounting for several percent more (one source ^[8] says 80%, but the reference they cite says nothing about nitrite)*. Whatever the amount, neither the NGO nor the WHO would ever dare propose banning vegetables.

Global warming of death

Nitrites are turning out to be like dietary cholesterol: people heard it's harmful, they just won't accept the new data, so they keep citing each other. Maybe the new data will turn out to be wrong. The new results might also be biased because they appeared just as 3-nitrooxypropanol (3-NOP, aka Bovaer), a nitrite-forming chemical given to cows to reduce supposed cow-induced global warming, came into use. If activists decide that pigs cause global warming, we can expect more politicized science: nitrite-forming compounds prevent formation of methane, but they also, it's claimed, cause cancer. Until we get some unbiased facts, we shouldn't base science policy on flimsy evidence like that on an activist website.

Nitrite and nitrate metabolism of death

Until recently, it was believed that most nitrite was produced from nitrate by commensal anaerobic bacteria in deep crypts in the tongue or in the stomach. The finding that leafy vegetables could be a major source of nitrite and the recognition that the nitrate and nitrite serve as reservoirs for nitric oxide (NO) ^[15], a dissolved gas that performs essential biological functions, throw a huge monkey wrench into this simple picture. Yes, that's a mixed metaphor, but that's not important right now.

Nitrate is concentrated in the mouth by the nitrate/proton transporter protein sialin. Bacteria located in the tongue convert nitrate to nitrite by nitrate reductase enzymes.^[16] Nitrate is also converted to NO by enzymes in the xanthine oxidation-reductase pathway.

Nitrite is reduced to NO non-enzymatically in the acidic environment of the stomach. It's also converted to NO by enzymes including xanthine oxidase, cytochrome C oxidase, endothelial NO synthase (eNOS), and possibly even deoxyhemoglobin.^[18] Nitrite in blood is rapidly converted to nitrate with a half life of 110 seconds,^[15] which means it could never reach a toxic level from dietary sources. (Normal levels are 50–100 nanomoles per liter). Under periods of ischemia, when vasodilation is badly needed, nitrite and nitrate are important donors of NO. In ischema, iNOS (inducible nitric oxide synthase)^[17] also produces NO. Thus, like iNOS, nitrite can be thought of as a regulator of hypoxic signaling.^[18]

All this fascinating biochemistry stuff means that the risk, if any, depends on the concentration × time (what pharmacol­ogists call area under the curve) and on the rates of the various reactions: nitrate to nitrite, nitrite back to nitrate, nitrite to nitrosamine, and nitrite to NO, in different parts of the body, or ‘compartments.’

There is still debate on the topic, and some understanding of toxicology will help, so I included eleven references to the primary literature here.

Alternatives of death

Alternatives such as bamboo leaf extract, rose extract, oregano oil, radish powder, kimchi powder, nisin nanoparticles, and potassium bixinate can prevent formation of N-nitrosamines ^[9] but they all have disadvantages, so nitrite is still essential. Gamma radiation seems to be the most effective alternative. (Note that this could affect the taste but would not make your bacon radioactive.) And of course, you can buy nitrite-free bacon today in many grocery stores if you so desire. But to get nitrite-free lettuce, you'd have to buy lettuce frozen at the farm and store it continuously in the freezer. And then you'd have to somehow convince yourself to eat it.

* Both the technical and popular literature are full of typos on this topic. Instead of ‘nitrite’ and ‘nitrate,’ authors should always write NO−2 and NO−3.

Footnotes

oct 29 2025, 10:39 am. updated oct 20 2025