Abstract
Study objectives—Colorectal cancer
(CRC) is a common cancer in many western
countries and is probably caused in
part by dietary factors. Southern European
countries have lower incidence rates
of CRC than many other western countries.
It was postulated that, because olive
oil is thought to influence bile salt secretion
patterns in rats, it may influence the
occurrence of CRC. The purpose of this
study was to compare national levels of
dietary factors, with particular reference
to olive oil, with national diVerences in
CRC incidence.
Design—Ecological study using existing
international databases. Incidence rates
for CRC, food supply data, and olive oil
consumption data were extracted from
published sources, combined, and analysed
to calculate the correlations between
CRC and 10 dietary factors. Associations
were then explored using stepwise multiple
regression.
Setting—28 countries from four continents.
Main results—76% of the intercountry
variation in CRC incidence rates was
explained by three significant dietary
factors—meat, fish and olive oil—in combination.
Meat and fish were positively
associated, and olive oil was negatively
associated, with CRC incidence.
Conclusion—Olive oil may have a protective
eVect on the development of CRC.
The proposed hypothesis is that olive oil
may influence secondary bile acid patterns
in the colon that, in turn, might
influence polyamine metabolism in colonic
enterocytes in ways that reduce progression
from normalmucosa to adenoma
and carcinoma.
(J Epidemiol Community Health 2000;54:756–760)