Submitted to: International Journal of Food Sciences and Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 2007
Publication Date: May 1, 2008
Citation: Burri, B.J., Chapman, M.H., Neidlinger, T.R., Seo, J., Ishida, B.K. 2008. Tangerine tomatoes increase total and tetra-cis-lycopene isomer concentrations more than red tomatoes in healthy adult humans. International Journal of Food Sciences and Nutrition. DOI: 10.1080/09637480701782084, 1-16, iFirst article. Interpretive Summary: Epidemiological studies show that people who eat greater than average amounts of fruits and vegetables have lower risks of premature death from cancer. One of the largest and most consistent differences in these two populations is a difference in the amount of carotenoids consumed. The overwhelmingly positive data from such studies led to clinical trials using purified B-carotene supplements to delay cancer incidence. Clinical trial results did not match the promise suggested by epidemiological associations, probably because most of the volunteers had adequate B-carotene status and because of excessively high dosage in the trials. Research now suggests that maximum benefit from '-carotene is provided by moderate dosages, approximately one-tenth of that provided in these clinical trials. The most likely reason for this miscalculation was the higher bioavailability of the B-carotene in supplements used than in foods. Because of difficulty in translating supplement studies to dietary recommendations, studies using foods are preferable. This is seldom done, because exchanging foods is usually complex in biochemical terms. We report a study in which we exchanged tetra-cis lycopene-rich Tangerine tomatoes for trans lycopene-rich red tomatoes. Lycopene is the most abundant carotenoid found in the blood of people in the United States. It is associated with antioxidant status, gap-junction formation, and inhibition of cholesterol synthesis. Epidemiological studies suggest that high lycopene intakes are associated with decreased risks for cancer and heart disease, with an especially strong correlation with prostate cancer. In vitro studies show that lycopene inhibits growth of human endometrial, lung, and mammary cancer cells much more effectively than B-carotene. Animal studies show that lycopene can inhibit brain and breast tumorigenesis. Lycopene is an acyclic carotenoid having 11 conjugated double bonds, making it a powerful antioxidant. There are many isomers of lycopene: an all-trans isomer and many cis isomers. About 90% of total lycopene is all-trans isomer in common red tomatoes. However, approximately 90% of the lycopene found in tangerine tomatoes (Lycoperison esculentum var. Tangella) is the tetra-cis isomer (7Z, 9Z, 7'Z, 9'Z)-lycopene (18 - 19). The isomeric form of lycopene probably does not influence its antioxidant properties. However, experimental evidence indicates that it might exert a powerful influence on the rate of uptake and maximal amount of lycopene absorbed by the human body. In the ferret, a common animal model for human carotenoid metabolism, cis-lycopene absorption is significantly greater than that of trans lycopene. Although virtually all lycopene in plants is in the all-trans form, a higher percentage of the cis configuration occurs in human blood. Furthermore, humans absorbed lycopene from processed tomato juice (boiled for one hour, and thus containing 20% cis lycopene) more efficiently than from fresh tomatoes and tomato juice, which contained less than 5% cis lycopene. Such evidence suggests that some cis isomers of lycopene are more easily absorbed than trans lycopene. It then follows that tomatoes rich in these forms of cis lycopene would be better food sources of lycopene then trans lycopene-rich tomatoes. We fed controlled diets to healthy human subjects in a randomized, crossover design to determine whether tetra-cis-rich Tangerine tomatoes had more bioavailable lycopene than trans lycopene-rich red tomatoes.
Technical Abstract: Lycopene may prevent prostate cancer. Since cis- lycopene isomers have been shown to be more bioavailable than the trans isomer, Tangerine tomatoes, in which most of their lycopene occurs as the tetra-cis isomer, should be a good source of highly bioavailable lycopene. We fed 24 healthy adults lunches containing 300 g Tangerine or common red tomato sauce per day in a double-blind, randomized crossover design. We collected blood at baseline and weekly thereafter. We measured tetra-cis, other cis, and trans lycopene, as well as other carotenoids, by reversed-phase HPLC. Both Tangerine and common red tomato sauce ingestion increased lycopene concentrations in blood, but when the sauces were normalized for their total lycopene concentrations, the tetra-cis-rich Tangerine tomato sauce was more bioavailable. Moreover, our evidence suggests that the cis isomer(s) facilitated absorption of the trans-lycopene isomer. Indices of oxidative damage decreased as serum lycopene concentrations increased, as expected.