nitrosamine
Meaning of nitrosamine: Chemicals that assemble wherever nitrite meets the right partner, including inside the stomach, and that damage DNA once the liver has processed them.
Definition of nitrosamine
A nitrosamine is any of a family of compounds in which a nitroso group is attached to a nitrogen atom carrying two carbon chains. They form where nitrite meets certain nitrogen-containing compounds, a reaction encouraged by heat, by curing salts and by the acid of the stomach. Most need processing by liver enzymes before they harm DNA, and several are established human carcinogens.
Where do they come from?
| Source | How they form there |
|---|---|
| Tobacco curing and smoke | Nicotine-related compounds react with nitrogen oxides |
| Cured and processed meat | Added nitrite reacts with amines, helped by high heat |
| The stomach | Dietary nitrate becomes nitrite and meets amines from protein |
| Beer and malted foods | Direct-fired kilning exposes malt to nitrogen oxides |
| Rubber, cosmetics, cutting fluid | Unintended by-products of manufacture |
Medicines belong on that list too. Trace nitrosamine contamination has been found in several unrelated drug classes, traced to reagents, solvents and recycled materials in manufacture, and it has prompted recalls of products with no connection to tobacco or diet.
How do they cause cancer?
Not directly. A nitrosamine arriving in the body is fairly inert. Liver enzymes, and similar enzymes in other tissues, attempt to break it down and in doing so create a short-lived fragment that latches onto a base in DNA. The cell then miscopies that base at its next division, and the change is permanent. Where the mistake lands in a gene controlling growth or repair, the descendants of that cell gain an advantage they should not have. Which tissue is hit depends on which enzymes handle the particular compound, which is why individual members produce tumors reliably in the liver, the esophagus, the lung or the bladder of laboratory animals rather than scattering at random.
How much exposure matters?
For a substance that damages DNA directly there is no level assumed to be entirely safe, so limits are framed around holding lifetime intake low rather than around a threshold. Total exposure over years is what counts, and smoking supplies by far the largest routine dose, including through environmental tobacco smoke. Formation is also preventable in part: vitamin C added during curing competes for the nitrite and suppresses the reaction, which is one reason nitrosamine content varies widely between products that look identical on a label. Diets heavy in processed meat are among the exposures examined in studies of colorectal cancer.
Also known as
Used in a sentence
The tobacco-specific nitrosamine content of the product was measured in the laboratory.
Good to know
Nitrosamines generally require activation by liver enzymes before they damage DNA, and vitamin C added during curing suppresses their formation, so the amount present in a food depends on how it was made rather than on its nitrite content alone.