Lycopene May Decrease Prostate Cancer Risk
Tomatoes are a rich source of lycopene.
Two recently published studies suggest that lycopene may help protect against the development of prostate cancer (PCa).
In one study, researchers led by Edward Giovannucci, MD, ScD, of the Harvard School of Public Health in Boston, found that increased dietary intake of lycopene is associated with a decreased risk of PCa, especially lethal PCa. They also showed that higher lycopene intake is associated with lower angiogenic potential in tumors based on vessel size and shape.
“Based on these results, we hypothesize that the consumption of a diet rich in lycopene-containing foods reduces the aggressive potential of prostate cancer by inhibiting the neoangiogenesis that occurs in tumor development,” Dr. Giovannucci's team reported online ahead of print in the Journal of the National Cancer Institute.
In the other study, Simone Mariani, MD, of Sant'Andrea Hospital and Fabia Mater Hospital, both in Rome, and collaborators found that low prostatic lycopene levels are associated with a greater likelihood of PCa. In a paper published in the International Journal of Molecular Sciences (2014;15:1433-1440), the investigators said their findings point to prostatic lycopene level as a promising biomarker of PCa.
Lycopene is a carotenoid found in abundance in tomato, tomato-based products, pink grapefruit, and watermelon, Dr. Giovannucci and his colleagues explained. In a meta-analysis of studies published up to 2003, high intakes of tomato or tomato-based products was associated with a 10%-20% decrease in PCa risk and high serum or plasma concentrations of lycopene were associated with a 25% decreased risk, they noted.
Dr. Giovannucci and his group studied 49,898 male health professionals who provided dietary information through questionnaires. Men in the highest quintile of dietary lycopene intake had a significant 9% decreased risk of PCa overall and a 28% decreased risk of lethal PCa compared with those in the bottom quintile, after adjusting for multiple variables. When the researchers limited their analysis to men who had at least one negative PSA screening test, subjects in the highest quintile had a significant 53% decreased risk of lethal PCa compared with those in the lowest quintile.
Study subjects were participants in the Health Professionals Follow-up study, an ongoing prospective cohort study consisting of 51,529 U.S. male dentists, osteopaths, podiatrists, pharmacists, and veterinarians aged 40-75 years at baseline in 1986.
The study by Dr. Mariani and colleagues included 32 patients with prostatic high-grade intraepithelial neoplasia (HGPIN), a pre-cancerous lesion. The investigators instructed subjects to consume 20-25 mg/day of lycopene through dietary supplementation for six months.
Patients underwent a six-month follow-up prostate biopsy and were classified into three groups based on histopathologic findings: prostatitis (seven patients), HGPIN (16 patients), and PCa (nine patients). The researchers measured PSA and plasma lycopene levels before and after the lycopene supplementation, but measured prostatic lycopene level only after supplementation. Only prostatic lycopene level was significantly different among the three groups, with a level below 1 ng/mg significantly associated only with PCa.
Of the nine patients with PCa, seven (77.8%) had a prostatic lycopene level below 1 ng/mg compared with only one (6.3%) of 16 patients with HGPIN and none of the seven patients with prostatitis, the researchers reported.
Additionally, the investigators found no overall benefits from lycopene supplementation, as the rate of HGPIN progression to PCa in the study cohort was similar to rates reported in the literature. The study also revealed no significant change in PSA levels from baseline.
In a recently published systematic review and meta-analysis in the Journal of Nutritional Science and Vitaminology (2013;59:213-223), Chinese investigators found that consumers of the highest intake of raw tomato had a 19% decreased risk of PCa compared with those who had the lowest intake.
The meta-analysis, which examined data from six prospective cohort studies and 11 prospective nested case-control studies, also found that consumers of the highest levels of cooked tomato intake versus the lowest intake had a 15% decreased risk. The highest intake of lycopene was associated with a 7% decreased risk of PCa compared with the lowest intake.
The researchers noted that their meta-analysis does not strongly support a positive association between lycopene or tomato intake with decreasing PCa, it does provide “reasonable evidence that research on lycopene/tomato intake in association of prostate health should be carried out among more geographical and age groups and correlation of lycopene intake and plasma lycopene should be examined.”