Lycopene

What does it do? Lycopene, found primarily in tomatoes, is a member of the carotenoid family—which includes beta-carotene and similar compounds found naturally in food—and has potent antioxidant capabilities.

A study conducted by Harvard researchers examined the relationship between carotenoids and the risk of prostate cancer.1 Of the carotenoids studied, only lycopene was clearly linked to protection. The men who had the greatest amounts of lycopene in their diet (6.5 mg per day or more) showed a 21% decreased risk of prostate cancer compared with those eating the least. This report suggests that lycopene may be an important tool in the prevention of prostate cancer. This study also reported that those who ate more than ten servings per week of tomato-based foods had a 35% decreased risk of prostate cancer compared with those eating less than 1.5 weekly servings. When the researchers looked at only advanced prostate cancer, the high lycopene eaters had an 86% decreased risk (although this did not reach statistical significance due to the small number of cases).

Contrary to popular opinion, research suggests that there is no preferential concentration of lycopene in prostate tissue.2 Although prostate cancer patients have been reported to have low levels of lycopene in the blood,3 and lycopene appears to be a potent inhibitor of human cancer cells in test-tubes,4 evidence is conflicting concerning whether an increased intake of tomato products is protective against prostate cancer. Some studies, like the one discussed above, have reported that high consumption of tomatoes and tomato products reduces risk of prostate cancer.5 6 Other studies, however, are inconclusive,7 and some have found no protective association.8 9 10 11 12

There is some evidence that lycopene may be helpful in the treatment of prostate cancer. In a preliminary trial, 26 men with prostate cancer were randomly assigned to receive lycopene (15 mg twice a day) or no lycopene for three weeks before undergoing prostate surgery. Prostate tissue was then obtained during surgery and examined. Compared with the unsupplemented men, those receiving lycopene were found to have significantly less aggressive growth of cancer cells.13 In addition, a case report has been published of a 62-year-old man with advanced prostate cancer who experienced a regression of his tumor after starting 10 mg of lycopene per day and 300 mg of saw palmetto three times per day. As saw palmetto has not been previously associated with improvements in prostate cancer, the authors of the report attributed the response to the lycopene.14 Long-term controlled studies are needed to confirm these promising initial reports.

There is no evidence that tomato intake has any effect on benign prostatic hyperplasia (BPH).

Another study found that for the 25% of people with the greatest tomato intake, the risk for cancers of the gastrointestinal tract was 30–60% lower, compared with those who ate fewer tomatoes. These reduced risks were statistically significant.15 A study of women found that the 75% who ate the least amount of tomatoes had between 3.5 and 4.7 times the risk for cervical intraepithelial neoplasia—pre-cancerous changes of the cervix.16 Other researchers have also reported evidence suggesting that high dietary lycopene may be linked to protection from cervical dysplasia.17 While preliminary evidence also links dietary lycopene with protection from breast cancer,18 another study did not find this link.19

In a review of 72 studies,20 one researcher reported 57 associations between tomato intake or blood lycopene levels and decreased risk of cancer. Of these associations, 35 were statistically significant. The benefit was strongest for prostate, lung, and stomach cancers, although protective associations were also found for cancers of the pancreas, colon, rectum, esophagus, oral cavity, breast, and cervix. Because the data were from observational studies, a cause-and-effect relationship cannot be firmly established. However, the consistently lower risk of cancer associated with higher consumption of lycopene-containing tomatoes, provides a strong foundation for further research on lycopene.

In Europe, researchers have found a statistically significant association between high dietary lycopene and a 48% lower risk of heart disease.21 Lycopene supplementation has also boosted immune function in the elderly. In that trial, 15 mg of lycopene per day increased natural killer cell activity by 28% in 12 weeks.22

Where is it found? Tomatoes and tomato-containing foods are high in lycopene. In the Harvard study, the only tomato-based food that did not correlate with protection was tomato juice. In an unblinded, controlled trial, lycopene supplementation, but not tomato juice, effectively increased the body’s lycopene stores.23 These studies suggest that the lycopene present in tomato juice is poorly absorbed. However, other research indicates that significant amounts of lycopene from tomato juice can, in fact, be absorbed.24 Other foods that contain lycopene include watermelon, pink grapefruit, and guava.

Lycopene has been used in connection with the following conditions (refer to the individual health concern for complete information):

Rating Health Concerns
2Stars Asthma, exercise-induced
Prostate cancer
1Star Atherosclerosis (prevention only)
Cancer risk reduction
Immune function
Macular degeneration
3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star An herb is primarily supported by traditional use, or the herb or supplement has little scientific support and/or minimal health benefit.

Who is likely to be deficient? This is unknown, but people who do not eat diets high in tomatoes or tomato products are likely to consume less than optimal amounts.

How much is usually taken? The ideal intake of lycopene is currently unknown; however, the men in the Harvard study with the greatest protection against cancer consumed at least 6.5 mg per day.

Are there any side effects or interactions? No adverse effects have been reported with the use of lycopene.

At the time of writing, there were no well-known drug interactions with lycopene.

References:

1. Giovannucci E, Ascherio A, Rimm EB, et al. Intake of carotenoids and retinol in relation to risk of prostate cancer. J Natl Cancer Inst 1995;87:1767–76.

2. Kristal AR, Cohen JH. Invited commentary: tomatoes, lycopene, and prostate cancer. How strong is the evidence? Am J Epidemiol 2000;151:124–7 [review, discussion 128–30].

3. Rao AV, Fleshner N, Agarwal S. Serum and tissue lycopene and biomarkers of oxidation in prostate cancer patients: a case-control study. Nutr Cancer 1999;33:159–64.

4. Levy J, Bosin E, Feldman B, et al. Lycopene is a more potent inhibitory of human cancer cell proliferation than either alpha-carotene or beta-carotene. Nutr Cancer 1995;24:257–66.

5. Mills PK, Beeson WL, Phillips RL, Fraser GE. Cohort study of diet, lifestyle, and prostate cancer in Adventist men. Cancer 1989;64:598–604.

6. Tzonou A, Signorello LB, Lagiou P, et al. Diet and cancer of the prostate: a case-control study in Greece. Int J Cancer 1999;80:704–8.

7. Norrish AE, Jackson RT, Sharpe SJ, Skeaff CM. Prostate cancer and dietary carotenoids. Am J Epidemiol 2000;151:119–23.

8. Deneo H-Pellegrini H, De Stefani E, Ronco A, Mendilaharsu M. Foods, nutrients and prostate cancer: a case-control study in Uruguay. Br J Cancer 1999;80:591–7.

9. Schuman L, Mandel J, Radke A. Some selected features of the epidemiology of prostate cancer: Minneapolis-St. Paul, Minnesota case-control study, 1976–1979. In: Magnus K (ed). Trends in cancer incidence: causes and implications. Washington, DC: Hemisphere Publishing Corporation, 1982, 345–54.

10. Key TJ, Silcocks PB, Davey GK, et al. A case-control study of diet and prostate cancer. Br J Cancer 1997;76:678–87.

11. Schuurman AG, Goldbohm RA, Dorant E, et al. Vegetable and fruit consumption and prostate cancer risk: a cohort study in The Netherlands. Cancer Epidemiol Biomarkers Prev 1998;7:673–80.

12. Hennekens CH, Buring JE, Manson JE, et al. Lack of effect of long-term supplementation with beta carotene on the incidence of malignant neoplasms and cardiovascular disease. N Engl J Med 1996;334:1145–9.

13. Kucuk O, Sarkar FH, Sakr W, et al. Phase II randomized clinical trial of lycopene supplementation before radical prostatectomy. Cancer Epidemiol Biomarkers Prev 2001;10:861–8.

14. Matlaga BR, Hall MC, Stindt D, Torti FM. Response of hormone refractory prostate cancer to lycopene. J Urol 2001;166:613.

15. Franceshci S, Bidoli E, La Vecchia C, et al. Tomatoes and risk of digestive-tract cancers. Int J Cancer 1994;59:181–4.

16. Van Eenwyk J, Davis FG, Bowne PE. Dietary and serum carotenoids and cervical intraepithelial neoplasia. Int J Cancer 1991;48:34–8.

17. Kanetsky PA, Gammon MD, Mandelblatt J, et al. Dietary intake and blood levels of lycopene: association with cervical dysplasia among non-hispanic, black women. Nutr Cancer 1998;31:31–40.

18. Dorgan JF, Sowell A, Swanson CA, et al. Relationships of serum carotenoids, retinol, alpha-tocopherol, and selenium with breast cancer risk: results from a prospective study in Columbia, Missouri. Cancer Causes Control 1998;9:89–97.

19. Jarvinen R, Knekt P, Seppanen R, Teppo L. Diet and breast cancer in a cohort of Finnish women. Cancer Lett 1997;114:251–3.

20. Giovannucci E. Tomatoes, tomato-based products, lycopene, and cancer: review of the epidemiologic literature. J Natl Cancer Inst 1999;91:317–31.

21. Kohlmeyer L, Kark JD, Gomez-Gracia E, et al. Lycopene and myocardial infarction risk in the EUROMIC study. Am J Epidemiol 1997;146:618–26.

22. Corridan BM, O’Donohue MP, Morrissey PA. Carotenoids and immune response in elderly people. Proc Nutr Soc 1998;57:3A [abstr].

23. Paetau I, Rao D, Wiley ER, et al. Carotenoids in human buccal mucosa cells after 4 wk of supplementation with tomato juice or lycopene supplements. Am J Clin Nutr 1999;70:490–4.

24. Paetau I, Khachik F, Brown ED, et al. Chronic ingestion of lycopene-rich tomato juice or lycopene supplements significantly increases plasma concentrations of lycopene and related tomato carotenoids in humans. Am J Clin Nutr 1998;68:1187–95.