Epidemiological studies suggest protective effects of
lycopene-rich foods on several types of
cancer, including prostate and gastrointestinal tract. Moreover, an inverse association between serum
lycopene concentrations and several types of
cancer has been reported. However, few studies have focused on
breast cancer, and they have shown little association between
lycopene consumption and
cancer risk. In this report, we used the N-
methylnitrosourea (NMU)-induced rat mammary
tumor model to compare the effects of pure
lycopene with a
lycopene-rich tomato
carotenoid oleoresin (TCO) on NMU-induced mammary
tumorigenesis. Rats were fed diets supplemented with 250 and 500 ppm crystalline
lycopene or TCO beginning seven days before initiation with NMU (55 days of age) to termination (18 wk after NMU). Neither pure
lycopene nor
lycopene in the form of a mixed
carotenoid oleoresin exerted an inhibitory effect on
tumor incidence, latency, multiplicity, volume, or total
tumors per group compared with unsupplemented controls.
Weight gains in all groups were similar. Assay of serum
lycopene concentrations in
lycopene-supplemented groups indicated that median levels of 7,12,60, and 87 ng/ml were attained in blood of groups supplemented with 250 and 500 ppm
lycopene and 250 and 500 ppm TCO, respectively. The results of this animal study are consistent with epidemiological reports indicating that
lycopene does not protect against
breast cancer.