The presence of fat in the stomach may override the anti-cancer effects of vitamin C, research suggests, BBC?News Online reports.
In laboratory experiments, a team at the University of Glasgow simulated what happens in the human stomach.
They found vitamin C (ascorbic acid) mopped up potential cancer-causing compounds that are made when saliva and food mixes with stomach acid.
But when they added fat, the ascorbic acid could no longer convert the hazardous compounds into safe ones.
The scientists say their findings show how diet might be linked to certain stomach cancers.
Nitrite, which is present in saliva and comes from nitrate in our diet, is thought to be able to trigger gastric cancer. When it is swallowed and enters the acidic environment of the stomach, nitrite spontaneously forms nitrosating species, and these are able to convert a range of other stomach chemicals into potential cancer-causing agents called N-nitrosocompounds.
Antioxidants like ascorbic acid protect against the formation of these nitrosocompounds by converting the nitrosating species into nitric oxide.
However, when fat is present, it reacts with the nitric oxide to reform nitrosating species, the scientists found.
The research was presented at the annual meeting of the Society of Experimental Biology.