What Is It?
Lycopene provides the red color to tomato products and is one of the major carotenoids in the diet of North Americans and Europeans. Lycopene is a prominent member of the carotenoid family. In plants, lycopene is similar to other carotenoids, serving as a light-absorbing pigment during photosynthesis and protecting cells against photosensitization. Interest is growing in lycopene because of the many recent epidemiological studies implicating lycopene in the prevention of cancer and cardiovascular disease. A diet rich in foods containing carotenoids is associated with several health benefits. Lycopene has unique structural and chemical features that may contribute to its biological actions in humans.
More than 80% of lycopene consumed in the United States is derived from tomato products, although apricots, papaya, pink grapefruit, guava, and watermelon also contribute to dietary intake. Lycopene content of tomatoes can vary significantly, depending on type of tomato and ripening. In the reddest strains of tomatoes, lycopene concentration is close to 50 mg per kg compared with only 5 mg per kg in the yellow strains. Lycopene appears to be relatively stable during cooking and food processing. Bioavailability of lycopene is influenced by heat and lipids. Heating foods prior to eating can improve lycopene absorption in the body. Further, fat also seems to enhance lycopene absorption from the gastrointestinal tract. Several observations seem to support the concept that cooking and food processing enhance the bioavailability of carotenoids, including lycopene. Lycopene absorption may be greater after ingestion of tomato paste rather than fresh tomatoes.
Many of the reported health benefits of lycopene are attributed to its ability to protect cells against oxidative damage. Although there has been less research focused on lycopene compared to other carotenoids, studies suggest that lycopene is a more potent scavenger of oxygen radicals than other major dietary carotenoids.
The basic science of lycopene is currently being established along with efforts toward evidence-based human intervention studies. Several studies have reported anticancer effects of lycopene in cell culture where lycopene has demonstrated antiproliferative effects.
Two large case-control studies have linked lycopene to reduced risk of digestive tract cancer. In northern Iran, where esophageal cancer is common, a case-control study found that weekly tomato consumption was associated with a 40% reduction in cancer risk. A recent case-control study in Italy found that consumption of seven or more servings of tomato products per week, compared to less than two servings per week, was associated with a 50% reduced risk of gastric cancer.
Lycopene is also associated with a reduced risk of colon cancer. A recently published large case-control study from Italy demonstrated a reduced colon cancer risk, an odds ratio of 0.49-0.68, for subjects consuming tomato product daily compared to those consuming tomato products on a weekly basis.
An inverse relationship between breast cancer and lycopene has also been observed. A recent case-control study in Boston examined the relationship between lycopene in breast tissue and breast cancer risk. Studies in rats showed that rats treated with a lycopene-enriched tomato oleoresin developed fewer tumors and had smaller tumor volume than control rats.
Studies are exploring the link between lycopene and skin cancer. Results suggest the possibility that diets low in tomato products and lycopene could lead to reduced lycopene concentrations in the skin, placing a person at higher risk for sunlight-induced skin damage.
Several studies have also examined the relationship between prostate cancer and lycopene. One large prospective study was conducted on a cohort of Seventh Day Adventist men who completed a questionnaire in 1976 and were followed over a six-year period. Consumption of tomato products was significantly associated with a reduced risk of prostate cancer. The relative risk was 0.60 for men who consumed tomatoes more than five times per week, compared to those who consumed less than one serving per week. Another study, the largest, most comprehensive study evaluating prostate cancer risk and lycopene, studied a large cohort of men who completed a 131-item questionnaire in 1986 and every few years after. Men who had higher estimated lycopene in their diets had lower risk for prostate cancer. A risk reduction of 35% was observed for men who consumed 10 or more servings of tomato products per week compared to less than 1.5 servings per week. Interestingly, tomato sauce accounted for the strongest reduction in risk for any one specific food item.
The relationship between lycopenes and cardiovasular disease is also being studied. Scientists hypothesize that lycopene can positively influence cholesterol metabolism because of its antioxidant properties. Researchers suggest that lycopene may be able to moderately lower cholesterol levels.