Oxidative stress induced by highly reactive oxygen species (hROS) is recognized as an important mechanism in the causation of chronic diseases such as cancer, cardiovascular disease, osteoporosis and diabetes. Fruits and vegetables are good sources of several antioxidants including lycopene, of recent interest and available in the diet primarily from tomatoes and tomato products. Popular for its role in prostate health, lycopene also improves markers for and risk of multiple cancers, cardiovascular disease, osteoporosis, diabetes, hypertension, male infertility and macular degeneration. Epidemiological, tissue culture, animal and human studies show a beneficial role for lycopene in the prevention and possibly treatment of chronic diseases. Generally, lycopene intake of North Americans is low (≤1.86 mg/day) compared to 7 mg/day now recommended to maintain circulatory lycopene at levels consistent with providing beneficial effects. Ongoing and future research is warranted to increase our understanding of lycopene’s role in human diseases, its mechanisms of action and its use in the management of public health.
Lycopene has attracted attention for nearly 50 years for its biochemical and physiochemical properties. Since that time, epidemiological, in vitro, and in vivo animal and human experiments have provided support for lycopene’s antioxidant health benefits and its potential to reduce the risk of several cancers and cardiovascular disease (CVD). Lycopene is a natural pigment synthesized by plants and microorganisms, and the diet constitutes the primary source of lycopene for humans. The attractive red color of tomatoes is due to the presence of lycopene; this antioxidant carotenoid can also be found in watermelon, pink grapefruit, apricots and pink guava. Lycopene is an acyclic, highly unsaturated, straight chain hydrocarbon containing 13 double bonds. Lycopene is an isomer of beta-carotene but does not have provitamin A activity. Oxygen-derived free radicals known as reactive oxygen species (ROS) are generated endogenously through normal metabolic activity, lifestyle activities, and diet. ROS-related oxidative stress results in the damage of cellular components including lipids, proteins and DNA. Cellular damage and oxidation of cellular biomolecules has been implicated in the early stages and pathogenesis of various human chronic diseases. In contrast, lycopene is a potent antioxidant that provides protection against cellular damage caused by ROS13 and, therefore, may play an important role in disease prevention. More specifically, because of its high number of conjugated double bonds, lycopene exhibits higher (two and ten times) singlet oxygen quenching ability compared with beta-carotene and alphatocopherol, respectively.
Lycopene: Bioavailability and Isomerization
In human dietary intervention research, serum lycopene levels significantly increase after consuming tomato foods or lycopene supplementation. However, not all sources of lycopene are equally bioavailable. Ingested in its natural trans form, such as is prominent in tomatoes, lycopene is poorly absorbed whereas heat processing of tomatoes and tomato products induces isomerization of lycopene from all-trans to cis configuration in turn increasing its bioavailability. Remaining to be determined, however, is whether or not cisisomers are biologically more effective than trans-isomers once in the body.
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