This question is motivated by this Skeptics SE answer which refers to this article synopsised as:
Eating vegetables rich in nitrogen in the same meal with fish increases risks for liver cancer, finds a laboratory study.
The risk of liver cancer slightly increases when eating fish together with certain naturally high-nitrate vegetables in the same meal, report researchers in a recent issue of Toxicological Sciences.
Is this true and proven, by many reputable others?
The article itself doesn't make such strong claims.
... we conclude that the consumption of fish/vegetable meals appears to lead to only marginal increases of human cancer risk.
And that only based on a few theoretical assumptions. You can e.g. also assume that for cancer to develop you need the immune system to miss some problems which may be far less likely to happen when you introduce a very small effect. There is then an effective threshold that must be overcome. In such a scenario, the marginal increase wouldn't exist at all.
