Vette voeding doet de werking van antioxidanten verminderen.*
Uit Engels onderzoek blijkt dat vet in de voeding de werking van antioxidanten in de maag doet verminderen. De gevolgen zijn dat daardoor de kans op kanker in de maag sterk doet verhogen. In ons speeksel kunnen nitraten uit de voeding omgezet worden in nitrieten. Als die nitrieten in de maag komen worden, onder invloed van het maagzuur, deze omgezet in nitroverbindingen die kunnen leiden tot carcinogene N-nitroverbindingen. Antioxidanten in de voeding zoals vitamine C voorkomen dat deze laatste omzettingen kunnen plaats vinden door de nitroverbindingen om te zetten in stikstofoxide (NO). Vetten doen echter een reactie teweeg brengen tussen het NO en zuurstof waardoor weer nitroverbindingen ontstaan en dus het werk van de antioxidant teniet gedaan wordt.
Fat
In Stomach Overrides Effects Of Vitamin C
Fats in our stomach may reduce the protective
effects of antioxidants such as vitamin C. Scientists at the University of
Glasgow found that in the presence of lipid the ability of antioxidants, such as
ascorbic acid (the active component of vitamin C), to protect against the
generation of potential cancer-forming compounds in the stomach is less than
when no lipids are present. "Our results illustrate how diet can influence
gastric biochemistry", says Emilie Combet, the post-doctoral researcher
working on the project, who presented her results at the Society of Experimental
Biology's Annual Main Meeting.
The incidence of cancer of the proximal stomach has been increasing over the
last 20 years for which environmental factors, such as diet, certainly play a
part. Nitrite, which is present in our saliva and is derived from nitrate in our
diet, is thought to be a pre-carcinogen for gastric cancer. When it is swallowed
and enters the acidic environment of the stomach, nitrite spontaneously forms
nitrosating species able to convert a range of targets, such as secondary amines
and bile acids, into carcinogenic N-nitrosocompounds. Antioxidants such as
ascorbic acid protect against the formation of these nitrosocompounds by
converting the nitrosating species back into nitric oxide (NO). However, NO
diffuses rapidly to lipids, where it reacts with oxygen to reform nitrosating
species. The presence of lipids therefore overrides the protective effect of
vitamin C against the formation of harmful compounds.
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The research, funded by the World Cancer Research Fund, will investigate further
the impact of dietary lipids on gastric biochemistry and the fate of nitrite, in
relation to malignancies of the upper stomach.
(Mei 2007)