A chemical in vegetables
such as broccoli, cauliflower and cabbage can boost DNA
repair in cells and may stop them becoming cancerous,
a study says.
Another chemical in soy also performs
the same role, the Georgetown University team said.
Although a link has already been found
between eating these foods and a reduced cancer risk,
this research shows how that might happen.
The research is published in the British
Journal of Cancer.
Vegetables such as broccoli were found
to contain a compound called I3C.
And a chemical called genistein found
in soy beans.
The repair proteins, regulated by genes
called BRCA1 and BRCA2, are important for preventing damaged
genetic information being passed on to the next generation
of cells.
If people have a faulty BRCA gene they
are at a higher risk of developing some forms of cancer,
including breast, ovarian and prostate cancer.
Low amounts of the BRCA proteins are
seen in cancer cells, so the scientists propose higher
levels might prevent cancer developing.
Researchers suggest the ability of I3C
and genistein to boost the amount of BRCA proteins could
explain their protective effects.
'Clear process'
Professor Eliot Rosen, who led the research,
said: "Studies that monitor people's diets and their health
have found links between certain types of food and cancer
risk.
"However, before we can say a food protects
against cancer, we have to understand how it does this
at a molecular level."
He added: "It is now clear that the function
of crucial cancer genes can be influenced by compounds
in the things we eat.
"Our findings suggest a clear molecular
process that would explain the connection between diet
and cancer prevention."
Professor John Toy, medical director
of Cancer Research UK, which owns the British Journal
of Cancer, said: "Diet's role in cancer prevention is
complex.
"This research explores an interesting
hypothesis as to how certain components of diet can affect
cancer risk.
"The evidence is building that these
chemical compounds act on some of the genes inside cells
that help prevent cancer developing."
But he added: "We still don't know if
this is exactly how these chemicals might act in every
day life."
However he said it had been established
that eating a balanced diet, which was high in fibre plus
plenty of fruit and vegetables, lowered the risks of developing
many forms of cancer.
