Lycopene is carotenoid which is present in tomatoes, processed tomato products, and other fruits.
Lycopene is one of the most potent antioxidants in the diet.
Lycopene’s antioxidant property is twice as high as that of beta carotene and ten times higher than that of alpha tocopherol.
Lycopene is an acrylic isomer of beta carotene and it is synthesized by plants and microorganisms.
Lycopene is a 40-carbon molecule which is highly unsaturated and it contains 11 conjugated and 2 unconjugated double bonds. In nature, lycopene is predominantly found in an all-trans configuration.
Lycopene is the most predominant carotenoid in human plasma. In human plasma, e is present in an isomeric mixture, with 50% as cis isomers. Lycopene is also found to concentrate in the adrenal glands, testes, liver, and prostate gland.
Lycopene increases gap-junctional intercellular communication, and this action is believed to be responsible for enabling the transfer of growth-regulatory signals.
Lycopene has been hypothesized to prevent carcinogenesis and atherogenesis by protecting critical cellular biomolecules, lipids, lipoproteins, proteins, and DNA. Though the exact mechanism of action has not been defined, researchers have found that patients with prostate cancer were found to have low levels of lycopene and high levels of oxidation of serum lipids and proteins.
Strong evidence exists from numerous studies which associate high serum or plasma lycopene with decreased risks of cancer of the lung, stomach, gastrointestinal tract and cancers of the colorectum.
Recent studies have also reported a decrease in the risk of total cardiovascular disease with higher concentrations of plasma lycopene.
Other studies have shown an inverse association between plasma lycopene and mortality in patients with prior cancers particularly in Oral, Pharynx, or Larynx Cancers.
Dietary intake of tomatoes and tomato products has been found to be associated with lower risk of a variety of cancers. One study observed a 35% reduction in the risk of developing prostate cancer among men who consumed 10 or more servings of tomato products per week. Other studies have shown that high levels of serum lycopene were inversely associated with the risk of breast cancer and prostate cancer.
Estimating the average daily intake of lycopene has been difficult due to the variability in reported levels in different foods. In the United States it has been estimated that the average daily intake of lycopene is about 3.7 mg to 6.5 per day (Schweitzer and others 1999 and NCC database).
In a recent study (Kucuk and Wood Jr., 2002), patients with diagnosed prostate cancer showed a decrease in plasma prostate specific antigen (PSA) after three weeks of lycopene supplementation in the amount of 15 mg twice/day. Tumor volume was also found to be smaller in the group which took Lycopene, and they also found the surgical stage of the tumors to be delayed. These observations suggest that lycopene may play a role in the treatment of cancers.
Lycopene is naturally present in red fruits and vegetables, including tomatoes, watermelons, pink grapefruits, apricots, and pink guavas. Processed tomato products such as juice, ketchup, paste, sauce, and soup are also good sources of lycopene. In comparing bioavailability values for lycopene, it appears that lycopene is more bioavailable from processed tomato products than from raw tomatoes. Estimating the average daily intake of lycopene has been difficult due to the variability in reported levels in different foods. In the United States it has been estimated that the average daily intake of lycopene is about 3.7 mg to 6.5 per day (Schweitzer and others 1999).
It is believed that processing and the presence of dietary lipids enhance lycopene bioavailability. Johnson and associates also found that the bioavailability of lycopene is significantly higher when it is was ingested along with other carotenoids than when ingested alone.
In recent studies serum and tissue levels of lycopene were shown to be inversely associated with the risk of breast cancer and prostate cancer. In a recent interventional study (Kucuk and Wood Jr., 2002) patients diagnosed with prostate cancer were given either 15 mg of lycopene twice/day or placebo capsules without lycopene for three weeks before surgery. The group supplemented with lycopene showed higher levels of plasma lycopene when compared to the control group. The plasma PSA levels in the treated group were also lower after receiving lycopene. In addition, the tumor volume in the treated group was also found to be smaller and the surgical stage of the tumors delayed. These observations led the researchers to conclude that lycopene may play a role in the treatment of cancers. 1
Lycopene has been hypothesized to prevent carcinogenesis and atherogenesis by protecting critical cellular biomolecules, including lipids, lipoproteins, proteins, and DNA. The most impressive results come from the US Health Professional Follow-up Study, which evaluated intakes of various carotenoids implementing the use of food frequency questionnaires, in relation to risk of prostate cancer. Prostate cancer risk decreased as lycopene intake increased. 23
A study published in the American Journal of Epidemiology in 2002 suggests that low concentrations of serum lycopene may be more strongly associated with aggressive prostate cancer. In their discussion, researchers state that their findings imply that disease progression may be especially susceptible to the protective effects of lycopene. This study was of particular importance because it included large numbers of US African Americans and they concluded that the results apply to this racial group. 4
In 2002, Kucuk and others discussed the effects on Lycopene supplementation in patients with localized prostate cancer. They once again confirmed what had been stated by Zhang and Bertram in 1991 and in 1992, that lycopene increased gap-junctional intercellular communication by increasing expression of the gap junctional gene, connexin 43. The report went on to state that their results suggest that lycopene may have an anti-tumor effect and perhaps be useful as an adjunct to standard treatments of prostate cancer, such as surgery, radiation therapy, hormones, and chemotherapy. 156
According to Erdhardt 2003, strong evidence exists from numerous experimental and epidemiological studies that high intakes of tomatoes and tomato-based products, as well as high serum or plasma lycopene concentrations, are associated with decreased risks of cancer of the lung, stomach, and prostate. Further published evidence suggests that lycopene may also play a role in protecting against cancers of the gastrointestinal tract, including cancers of the colorectum. 78
More recently, in 2004, Sesso and others reported that higher plasma lycopene concentrations are associated with lower risk of CVD in women. This analysis corrected for age, smoking, and adjustment for randomized treatment assignments and plasma cholesterol concentrations. The conclusion was that the risk of total CVD appeared to decrease with higher concentrations of plasma lycopene. Women with concentrations of plasma lycopene greater than 16.5 micrograms/dL had a possible 34% reduction in total CVD compared with those women in the lowest quartile, after multivariate adjustment. 910
In vitro studies indicate that of all major dietary carotenoids, lycopene is the most potent scavenger of reactive oxygen species. Preliminary in vitro evidence indicates that lycopene reduces cellular proliferation induced by insulin-like growth factors, which are potent mitogens, in various cancer cell lines. Lycopene also has been shown to act as a hypocholesterolemic agent by inhibiting HMG-CoA reductase (Fuhram 1997). 1112
Giovannucci recently reviewed 72 epidemiological studies including ecological, case control, dietary and blood-specimen-based investigations of tomatoes, tomato products, lycopene and cancer. 57 demonstrated an inverse relationship between circulating lycopene levels and the risk of several types of cancer; in 35 of these cases, the association was statically significant. 131415
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