Positive Health Online

Abstract

CLINTON and colleagues, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts USA write that the Health Professionals Follow-Up Study has indicated a lower prostate cancer risk associated with greater consumption of tomatoes and related foods. Tomatoes are the primary dietary source of lycopene, non-provitamin A carotenoid with potent antioxidant activity. The authors set out to define the concentrations of lycopene, other carotenoids and retinol in benign and malignant prostate tissue.

Background

Methodology

Involved in the study were 25 men aged 5374, undergoing prostatectomy for localised prostate cancer.

Results

The concentrations of specific carotenoids in benign and malignant prostate tissue from the same person were highly correlated. Lycopene and all-trans beta-carotene were the predominant carotenoids lycopene concentrations ranged from 0 2.58 nmol/g; all-trans beta-carotene concentrations from 0.09 1.70 nmol/g. 9-cis beta-carotene isomer, alpha-carotene, lutein, alpha-cryptoxanthin, zeaxanthin and beta-cryptoxanthin were consistently found in prostate tissue. There were no significant correlations between the concentration of lycopene and other carotenoids, although there were strong correlations between prostate beta-carotene and alpha-carotene and other carotenoid pairs, reflecting their similar dietary origins. Mean vitamin C concentrations was 1.52 nmol/g. All-trans lycopene accounts for 7991%, cis lycopene isomers for 921% of total lycopene in tomatoes, tomato paste and tomato soup. Lycopene concentrations in serum ranged between 0.60 1.9 nmol/ml with 2742% all-trans lycopene and 5873% cis-isomers. In contrast with foods, all-trans lycopene accounted for only 1221% and cis isomers for 7988% of total lycopene in benign or malignant prostate tissues.

Conclusion

There is a diverse array of carotenoids found in the human prostate with significant variation between individuals. The presence of lycopene in the prostate at concentrations which are biologically active in laboratory studies is supportive of the hypothesis that lycopene may affect the prostate directly and contribute to reduced prostate cancer risk associated with the consumption of tomato-based foods. Identification and development of geometric lycopene isomers may provide novel agents for future chemoprevention studies.

References

Clinton SK et al. cis-trans lycopene isomers, carotenoids, and retinol in the human prostate. Cancer Epidemiol Biomarkers Prev 5(10): 823-33. Oct 1996.