In stomach acid, nitrite reacts with amines from food to form N-nitroso compounds.The chain is real. Nitrosamines are not nitrite itself: the conversion product is the concern, and vitamin C and polyphenols inhibit that conversion.
2 · It cannot touch DNA; the liver makes it dangerous
When a nitrosamine first enters it is not very reactive, but liver enzymes oxidize it to drill a handle, and the intermediate is often far more reactive than the original.What is dangerous is often not the molecule you ate, but what the body makes while trying to process it.
3 · Only the fraction that slips repair is fixed as a mutation
The intermediate hangs a methyl group onto a DNA base; repair wipes most on the spot, and only the small fraction that slips through is fixed as a mutation.This kind of risk is counted by long-term frequency, not by a single meal.
4 · Every step is discounted; the rumor keeps only exists
From nitrite to mutation, every step has conditions that discount the risk, yet the rumor keeps only the word exists.Enough nitrite has to form, the stomach needs enough amines, conversion has to slip past vitamin C and polyphenols, and it still has to hit the narrow window where activation is fast and repair is slow. The rumor erases that string of discounts and leaves only the word exists. Look at total amount, not the word overnight.
Mechanism
Leftovers — the danger is the intermediate
Nitrosamines cannot touch DNA on their own; the liver oxidizes them into an intermediate.