What is lycopene?
Lycopene is a carotenoid (a natural pigment made by plants). Lycopene protects plants from stress and helps them use the energy of the sun to make nutrients. Lycopene is found in fruits and vegetables like tomatoes, apricots, guavas, and watermelons.
The main source of lycopene in the American diet is tomato-based products. Lycopene is more bioavailable (easier for the body to use) in processed tomato products like tomato paste and tomato puree than in raw tomatoes.
Eating carotenoids, including lycopene, along with dietary fat may help the body absorb them. For example, one study showed that more lycopene was absorbed from diced tomatoes cooked with olive oil than diced tomatoes cooked without olive oil.
Lycopene in the diet may affect antioxidant activity and communication between cells. Laboratory and animal studies have shown that lycopene may help lower the risk of prostate, skin, breast, lung, and liver cancers. However, clinical trials of whether lycopene lowers cancer risk have shown mixed results.
How is lycopene administered or consumed?
Lycopene may be consumed in the diet or taken in dietary supplements.
Have any preclinical (laboratory or animal) studies been conducted using lycopene?
Laboratory research and animal studies have been done to find out if lycopene may be useful in preventing or treating prostate cancer.
Studies of lycopene in the laboratory have shown the following:
- Prostate cancer cells treated with lycopene had changes in their cell division cycle, leading to less cancer cell growth.
- In prostate cancer cells treated with lycopene, cholesterol levels were lower, leading to less cancer cell growth & more cancer cell damage.
- Treating prostate cancer cells with lycopene may change the way androgen (male hormone) is taken up and used in the cells, causing less cancer cell growth.
- Combining lycopene with standard cancer drugs may help stop the growth of different types of prostate cancer cells more than when drugs are used alone. Used together with a cancer drug, lycopene may block the way insulin-like growth factor (IGF) is taken up by the cells, causing less cancer cell growth.
Studies of animal models of prostate cancer treated with lycopene have shown the following:
- Strains of mice created to develop prostate cancer that acts like human cancer were fed a diet with either lycopene beadlets or tomato paste. Mice on the lycopene beadlet diet had a greater decrease in prostate cancer rates than mice on the tomato paste diet. This suggests that lycopene might have more cancer protective effects than tomato paste.
- Combining lycopene with a substance found in dried tomatoes (FruHis) slowed the growth of prostate cancer cells in rats more than either lycopene or FruHis alone.
- A study of mice injected with human prostate cancer cells showed that mice treated with either lycopene or beta carotene supplements had less tumor growth.
- A study of mice injected with human prostate cancer cells and treated with a certain chemotherapy drug, lycopene, or both showed that those treated with chemotherapy and lycopene lived longer and had smaller tumors than those treated with chemotherapy alone.
Have any population studies or clinical trials (research studies with people) of lycopene been conducted?
Several population studies and clinical trials have been done to find out if lycopene may be useful in preventing or treating prostate cancer.
Population studies look for risk factors and ways to control disease in large groups of people. Population studies of prostate cancer risk have shown the following mixed results:
- Studies of large groups of men have found that high amounts of lycopene in the diet are linked with a lower risk of developing prostate cancer.
- Some studies have shown that lycopene levels in the blood and tissue of patients with cancer are lower than in those who do not have cancer. However, other studies have not shown this.
- Several studies found that men who ate more raw or cooked tomatoes had a slightly lower risk of prostate cancer.
- A study found no link between lycopene and tomatoes in the diet and prostate cancer risk in the overall population. However, in men with a family history of the disease, higher amounts of lycopene in the diet were linked with a lower risk of prostate cancer. Another study in the same group of men found no difference in blood levels of lycopene between healthy men and men who developed prostate cancer.
Many issues may be involved in these mixed findings, including sources and types of lycopene, other dietary differences, obesity, tobacco and alcohol use, and genetic risk factors.
Clinical trials of preventing prostate cancer
Clinical trials designed to study whether lycopene is useful in preventing prostate cancer have shown the following:
- Men with benign prostate hyperplasia (BPH) or prostate cancer were given tomato sauce dishes for 3 weeks before scheduled surgery to remove the prostate. The study found that they had markedly lower prostate specific antigen (PSA) levels and more cancer cell death found in the prostate when examined after surgery than a similar group of patients who did not receive the tomato sauce dishes.
- Men with high-grade prostatic intraepithelial neoplasia (HGPIN) who took lycopene supplements for 2 years had a greater decrease in PSA levels and fewer cases of prostate cancer than those who did not. This indicated that lycopene may be useful in preventing HGPIN from developing into prostate cancer. In another study of men at high risk of prostate cancer (such as men with HGPIN), those who took a daily multivitamin with no lycopene and those who took the same multivitamin plus lycopene (30 mg/ day) for 4 months showed no difference in PSA levels.
Clinical trials of treating prostate cancer
Clinical trials designed to study whether lycopene is useful in treating prostate cancer have shown the following:
- Men with prostate cancer that had not spread were given lycopene supplements (30mg/ day) for 3 weeks before surgery to remove the prostate. Those who received lycopene supplements had smaller tumors and lower PSA levels than those who did not. This study suggests that lycopene may be helpful in treating prostate cancer. Another study of men with prostate cancer that had not spread showed that men who took lycopene supplements (10mg/ day for 1 year) had lower PSA velocity (a measure of how fast PSA levels in the blood increase over time) after treatment.
- Men who had biochemical relapse of prostate cancer (a rise in the blood level of PSA after treatment with surgery or radiation) were given different doses of lycopene supplements (ranging from 15 mg/ day to 120 mg/ day) for 1 year. Study results showed that lycopene seemed safe & had no side effects, but did not change PSA levels in biochemically relapsed prostate cancer.
- Men with hormone-refractory prostate cancer (HRPC) (tumors that do not respond to treatment with hormones) were given lycopene supplements for periods of 3 or 6 months in 2 different studies. These studies showed mixed results in lowering PSA levels in men with HRPC.
- Men with androgen-independent prostate cancer (tumors that do not need androgen to grow) consumed lycopene in either tomato paste or tomato juice daily for 4 months. Study results showed that lycopene may not be effective in lowering PSA levels in androgen-independent cancer.
Have any side effects or risks been reported from lycopene?
Lycopene has been consumed by prostate cancer patients with very few side effects in many clinical trials. Doses ranging from 10 to 120 mg/ day have caused only occasional gastrointestinal symptoms (e.g. diarrhea, nausea and vomiting, bloating, gassiness and stomach irritation). In one study, symptoms went away when lycopene was taken with meals.
Is lycopene approved by the U.S. Food and Drug Administration (FDA) for use to prevent or treat cancer in the United States?
The U.S. Food and Drug Administration has not approved the use of lycopene as a treatment for cancer or any other medical condition.
Lycopene is available in the United States in food products and dietary supplements. Because dietary supplements are regulated as foods, not as drugs, FDA approval is not required unless specific claims about disease prevention or treatment are made. An FDA review in 2007 found that there was not enough evidence to allow a claim that lycopene helps lower cancer risk.