The presence of fat in the stomach may override the anti-cancer
effects of vitamin C, research suggests.
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 to the mix, 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.
Stomach chemicals
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.
Lead author Emilie Combet said: "These results show that the
presence of lipid can markedly alter the protective effects of
antioxidants, and how a diet rich in fat can directly influence
gastric biochemistry."
She presented her work at the annual meeting of the Society of
Experimental Biology.
Bridget Aisbitt, nutrition scientist for the British Nutrition
Foundation, said: "Cancer is a complex disease developed over many
years due to a number of genetic and environmental factors, so it's
important not to imply that any one factor can 'cause
cancer'.
"However, this research is interesting."
She said fat-compatible antioxidants in the body, such as
beta-carotene, could also neutralise the nitrosocompounds.
She advised: "This is another reason to underline the importance of
a healthy balanced diet where meals high in fat should not be
frequent and five portions of fruit and vegetables - our main
source of vitamin C - are eaten each day."
From BBCnews 