To review the effects of tomato product supplementation, containing lycopene, on biomarkers of oxidative stress and carcinogenesis in human clinical trials.
Supplementation of tomato products, containing lycopene, has been shown to lower biomarkers of oxidative stress and carcinogenesis in healthy and type II diabetic patients, and prostate cancer patients, respectively. Processed tomato products like tomato juice, tomato paste, tomato puree, tomato ketchup and tomato oleoresin have been shown to provide bioavailable sources of lycopene, with consequent increases in plasma lycopene levels versus baseline. Dietary fats enhance this process and should be consumed together with food sources of lycopene. The mechanisms of action involve protection of plasma lipoproteins, lymphocyte DNA and serum proteins against oxidative damage, and anticarcinogenic effects, including reduction of prostate-specific antigen, upregulation of connexin expression and overall decrease in prostate tumor aggressiveness. There is limited in vivo data on the health benefits of lycopene alone. Most of the clinical trials with tomato products suggest a synergistic action of lycopene with other nutrients, in lowering biomarkers of oxidative stress and carcinogenesis.
Consumption of processed tomato products, containing lycopene, is of significant health benefit and can be attributed to a combination of naturally occurring nutrients in tomatoes. Lycopene, the main tomato carotenoid, contributes to this effect, but its role per se remains to be investigated.
This study was supported by Human Nutrition Fund, Texas. AB wrote the first draft which was finalized by VI. VI also designed Figure 1.
An increased oxidative stress has been implicated in the incidence of chronic diseases. Dietary intakes of tomatoes and tomato products containing lycopene have been associated with a decreased risk of diseases such as cancer and cardiovascular diseases (CVDs) in numerous studies (Kohlmeier et al., 1997; Giovannucci et al., 2002; Sesso et al., 2003). Tomatoes account for 85% of lycopene consumption in an average American diet, and is an essential component of the Mediterranean diet, which is well known for its cardioprotective and anticarcinogenic health effects (La Vecchia, 1997; de Lorgeril et al., 1999). Tomatoes are a valuable source of several micronutrients and phytochemicals including carotenoids, polyphenols, potassium, folate, ascorbic acid and α-tocopherol. Most of these nutrients in tomatoes can interact with the host to confer a preventive benefit against oxidative stress-associated diseases, through various mechanisms including antioxidant action (Rao and Agarwal, 2000; Rao, 2002; Canene-Adams et al., 2005). However, the benefits of tomato intake have been mainly attributed to its lycopene content.
Bioavailability of lycopene
Although 90% of the lycopene in dietary sources is found in the linear, all-trans conformation, human tissues (particularly liver, adrenal, adipose tissue, testes and prostate) contain mainly cis-isomers. Holloway et al. (2000) reported that a dietary supplementation of tomato puree for 2 weeks in healthy volunteers led to a completely different isomer pattern of plasma lycopene in these volunteers, versus those present in tomato puree. 5-cis, 13-cis and 9-cis-lycopene isomers, not detected in tomato puree, were predominant in the serum (Holloway et al., 2000). Analysis of plasma lycopene in male participants in the Health Professionals Follow-up Study revealed 12 distinct cis-isomers and the total cis-lycopene contributed about 60–80% of total lycopene concentrations (Wu et al., 2003). Studies conducted with lymph cannulated ferrets have shown better absorption of cis-isomers and their subsequent enrichment in tissues (Boileau et al., 1999). Physiochemical studies also suggest that cis-isomer geometry accounts for more efficient incorporation of lycopene into mixed micelles in the lumen of the intestine and into chylomicrons by the enterocyte. cis-isomers are also preferentially incorporated by the liver into very low-density lipoprotein (VLDL) and get secreted into the blood (Britton, 1995). Research has shown convincing evidence regarding the isomerization of all-trans-lycopene to cis-isomers, under acidic conditions of the gastric juice. Incubation of lycopene derived from capsules with simulated gastric juice for 1 min showed a 40% cis-lycopene content, whereas the levels did not exceed 20% even after 3 h incubation with water as a control. However, when tomato puree was incubated for 3 h with simulated gastric juice, the cis-lycopene content was only 18%, versus 10% on incubation with water. Thus, gastric pH and food matrix influence isomerization and subsequent absorption and increased bioavailability of cis-lycopene (Re et al., 2001).
The process of cooking which releases lycopene from the matrix into the lipid phase of the meal, increases its bioavailability, and tomato paste and tomato puree are more bioavailable sources of lycopene than raw tomatoes (Gartner et al., 1997; Porrini et al., 1998). Factors such as certain fibers, fat substitutes, plant sterols and cholesterol-lowering drugs can interfere with the incorporation of lycopene into micelles, thus lowering its absorption (Boileau et al., 2002). Several clinical trials have also shown the bioavailability of lycopene from processed tomato products (Table 1). Agarwal and Rao (1998), reported a significant increase in serum lycopene levels following a 1-week daily consumption of spaghetti sauce (39 mg of lycopene), tomato juice (50 mg of lycopene) or tomato oleoresin (75 or 150 mg of lycopene), in comparison with the placebo, in healthy human volunteers. There was also indication that the lycopene levels increased in a dose-dependent manner in the case of tomato sauce and tomato oleoresin. Reboul et al. (2005) further demonstrated that enrichment of tomato paste with 6% tomato peel increases lycopene bioavailability in men, thereby suggesting the beneficial effects of peel enrichment, which are usually eliminated during tomato processing. Richelle et al. (2002) compared the bioavailability of lycopene from tomato paste and from lactolycopene formulation (lycopene from tomato oleoresin embedded in a whey protein matrix), and reported similar bioavailability of lycopene from the two sources in healthy subjects. Dietary fat has been shown to promote lycopene absorption, principally via stimulating bile production for the formation of bile acid micelles. Consumption of tomato products with olive oil or sunflower oil has been shown to produce an identical bioavailability of lycopene, although plasma antioxidant activity improved with olive oil consumption, suggesting a favorable impact of monounsaturated fatty acids on lycopene absorption and its antioxidant mechanism (Lee et al., 2000). In an interesting study, Unlu et al. (2005) reported the role of avocado lipids in enhancing lycopene absorption. In this study, in healthy, nonpregnant, nonsmoking adults, the addition of avocado fruit (75 or 150 g) or avocado oil (12 or 24 g) to salsa (300 g) enhanced lycopene absorption, resulting in 4.4 times the mean area under the concentration-versus-time curve after intake of avocado-free salsa. This study demonstrates the favorable impact of avocado consumption on lycopene absorption and has been attributed to the fatty acid distribution of avocados (∼66% oleic acid), which may facilitate the formation of chylomicrons. In a comparative study by Hoppe et al. (2003), both synthetic and tomato-based lycopene supplementation showed similar significant increases of serum total lycopene above baseline whereas no significant changes were found in the placebo group.
In an attempt to study lycopene metabolism, Diwadkar-Navsariwala et al. (2003) developed a physiological pharmacokinetic model to describe the disposition of lycopene, administered as a tomato beverage formulation at five graded doses (10, 30, 60, 90 or 120 mg) in healthy men. Blood was collected before dose administration and at scheduled intervals until 672 h. The overall results of this study showed that independent of dose, 80% of the subjects absorbed less than 6 mg of lycopene, suggesting a possible saturation of absorptive mechanisms. This may have important implications for planning clinical trials with pharmacological doses of lycopene in the control and prevention of chronic diseases, if absorption saturation occurs at normally consumed levels of dietary lycopene.
Mechanisms of action of lycopene
Cellular and molecular studies have shown lycopene to be one of the most potent antioxidants and has been suggested to prevent carcinogenesis and atherogenesis by protecting critical biomolecules such as DNA, proteins, lipids and low-density lipoproteins (LDLs) (Pool-Zobel et al., 1997; Agarwal and Rao, 1998; Rao and Agarwal, 1998). Lycopene, because of its high number of conjugated double bonds, exhibits higher singlet oxygen quenching ability compared to β-carotene or α-tocopherol (Di Mascio et al., 1989). cis-Lycopene has been shown to predominate in both benign and malignant prostate tissues, suggesting a possible beneficial effect of high cis-isomer concentrations, and also the involvement of tissue isomerases in in vivo isomerization from all trans to cis form (Clinton et al., 1996). Whereas Levin and co-workers (1997) have shown that 9-cis β-carotene is a better antioxidant than its all-trans counterpart, no such mechanistic data have been reported in case of individual lycopene isomers. Hadley et al. (2003) reported a significant increase in 5-cis lycopene concentrations following a 1-week lycopene-restricted diet, and a subsequent reduction in 5-cis, and a concomitant increase in cis-B, cis-D and cis-E lycopene isomers during the 15-day dietary intervention with tomato products in healthy individuals. Although this study reported a decrease in LDL oxidizability due to the intervention with tomato lycopene, the individual antioxidant role of lycopene isomers and their interconversions remain unclear.
At a physiological concentration of 0.3 μmol/l, lycopene has been shown to inhibit growth of non-neoplastic human prostate epithelial cells in vitro, through cell cycle arrest which may be of significant implications in preventing benign prostate hyperplasia, a risk factor for prostate cancer (Obermuller-Jevic et al., 2003). Lycopene has also been shown to significantly reduce LNCaP human prostate cancer cell survival in a dose-dependent manner, and this antineoplastic action may be explained by increased DNA damage at high lycopene concentrations (>5 μ M), whereas lower levels of lycopene reduced malondialdehyde formation, with no effects on DNA (Hwang and Bowen, 2005). Physiologically attainable concentrations of lycopene have been shown to induce mitochondrial apoptosis in LNCaP human prostate cancer cells, although no effects were observed on cellular proliferation or necrosis (Hantz et al., 2005). Animal studies have shown antineoplastic effects of both tomato powder and purified lycopene supplementation. Boileau et al. (2003) reported a significant inhibition of N-methyl-N-nitrosourea -testosterone-induced carcinogenesis in male Wistar-Unilever rats following consumption of tomato powder (13 mg lycopene/kg diet), whereas no effects were observed with lycopene supplementation per se (161 mg lycopene/kg diet). This study suggests the synergistic effects of lycopene with other antioxidants in tomatoes, in exerting an antineoplastic effect (Boileau et al., 2003). However, in the Dunning rat prostate cancer model, a 4-week supplementation with a higher concentration of lycopene beadlets (4 g lycopene/kg diet), revealed significant downregulation of 5-α-reductase, reduced steroid target genes expression and prostatic insulin-like growth factor-1 (IGF-1) and interleukin-6, thereby causing a subsequent reduction in the growth of tumor tissue (Siler et al., 2004). As evident from in vitro and animal studies, purified lycopene may inhibit prostate cancer growth only at higher concentrations, in comparison with tomato antioxidant supplementation. Karas et al. (2000) have further reported inhibitory effects of lycopene on MCF7 human mammary cancer cell growth, owing to interference in IGF-1 receptor signaling and cell cycle progression (Karas et al., 2000). Thus, interference in androgen metabolism, and inhibition of growth factors and cytokine activity, appear to be the major pathways through which lycopene inhibits prostate and breast cancer growth. Tomato lycopene supplementation (1.1 mg/kg/day corresponding to 15 mg lycopene intake in a 70 kg person) has also been shown to prevent the change in p53, p53 phosphorylation and p53 target genes, induced by cigarette smoke exposure in the gastric mucosa of ferrets. This further suggests a protective effect of lycopene against the development of gastric cancer (Liu et al., 2006). Studies using human and animal cells have identified a gene, connexin 43, correlated with reduced indexes of neoplasia, and whose expression is upregulated by lycopene and which allows direct intercellular gap junctional communication, thereby reducing the rate of proliferation (Stahl et al., 2000, Vine and Bertram, 2005).
Lycopene has also been shown to interfere in lipid metabolism, lipid oxidation and corresponding development of atherosclerosis. Lycopene treatment has been shown to cause a 73% suppression of cellular cholesterol synthesis in J-774A.1 macrophage cell line, and augment the activity of macrophage LDL receptors (Fuhrman et al., 1997). Oxidized LDLs are highly atherogenic as they stimulate cholesterol accumulation and foam cell formation, initiating the fatty streaks of atherosclerosis (Libby, 2006). LDL susceptibility to oxidative modifications is decreased by an acyl analog of platelet-activating factor (PAF), acyl-PAF, which exerts its beneficial role during the initiation and progression of atherosclerosis. Purified lycopene in association with α-tocopherol or tomato lipophilic extracts has been shown to enhance acyl-PAF biosynthesis in endothelial cells during oxidative stress (Balestrieri et al., 2004). Fuhrman et al (2000) further reported comparative data in which tomato oleoresin exhibited superior capacity to inhibit in vitro LDL oxidation in comparison with pure lycopene, by up to fivefold. A combination of purified lycopene (5 μmol/l) with α-tocopherol in the concentration range of 1–10 μmol/l resulted in a significant greater inhibition of in vitro LDL oxidation, than the expected additive individual inhibitions. In this study, purified lycopene was also shown to act synergistically with other natural antioxidants like the flavonoid glabridin, the phenolics rosmarinic acid and carnosic acid, and garlic in inhibiting LDL oxidation in vitro. These observations suggest a superior antiatherogenic characteristic of tomato oleoresin over pure lycopene. The combination of lycopene with other natural antioxidants, as in tomatoes, may be more potent in inhibiting lipid peroxidation, than lycopene per se.
Interestingly, whereas limited in vitro studies show convincing antioxidant and anticarcinogenic effects of lycopene, animal studies and several clinical trials report beneficial effects following consumption of tomato products containing lycopene. There exists limited in vivo data on the effects of lycopene per se. In this review, we will summarize the effects of lycopene supplementation, as tomato products or purified lycopene, on biomarkers of oxidative stress and carcinogenesis in clinical trials, with supporting epidemiological observations on dietary and plasma lycopene levels and the reduced incidence of certain types of cancer.
Tomato product supplementation and biomarkers of oxidative stress and carcinogenesis: clinical trials in healthy subjects, type II diabetic patients and prostate cancer patients
Table 1 summarizes the clinical trials investigating the effects of supplementation of tomato products or tomato oleoresin, containing lycopene, on biomarkers of oxidative stress and carcinogenesis. Several studies have shown the antioxidant effects of supplementation of tomato products or purified lycopene (providing 6–17 mg lycopene/day), on cellular DNA, in healthy human volunteers (Riso et al., 1999, 2004; Porrini and Riso, 2000; Porrini et al., 2002; Porrini et al., 2005; Zhao et al., 2006; Table 1). However, effects on lipid peroxidation have been somewhat conflicting. Riso et al. (2004) observed no effects on lymphocyte resistance from lipid oxidation, following a 3-week supplementation of tomato products (8 mg lycopene/day). Briviba et al. (2004) also reported null effects on lipid peroxidation in plasma and feces in healthy men following a 2-week supplementation of 330 ml/day of tomato juice. Hininger et al. (2001) further supplemented healthy male volunteers with 15 mg of natural tomato lycopene extracts for 12 weeks, and reported no effects on LDL oxidizability. In comparison with these studies showing null effects of tomato lycopene supplementation on lipoprotein oxidation, Bub et al. (2000) reported a 18% increase in LDL lag time in 23 healthy men, following a 2-week tomato juice consumption providing a higher dose of lycopene (40 mg/day). It should also be noted that following a 2-week carotenoid depletion period, the plasma lycopene levels in these healthy volunteers were reduced to a concentration of 0.16 μmol/l of all-trans lycopene and 0.15 μmol/l of cis-lycopene. Rao and Shen (2002) also reported a significant decrease in serum lipid peroxidation and protein oxidation in healthy volunteers, following a 2-week consumption of tomato ketchup or oleoresin capsules, with baseline serum lycopene levels less than 0.2 μmol/l. These baseline plasma lycopene levels were lower than those reported by Riso et al. (1999), Briviba et al. (2004) and Hininger et al. (2001) in their studies (0.34, 0.2 and 0.63 μmol/l, respectively). Thus, there may be a possibility that a depleted baseline lycopene level shows a better response to tomato antioxidant supplementation, than subjects with higher values. Kiokias and Gordon (2003) reported a significant decrease in biomarkers of oxidative stress in young healthy volunteers, following a 3-week supplementation of lycopene, in combination with other natural carotenoids. Chopra et al. (2000) also showed an increase in LDL lag time in healthy adults, following a 1-week supplementation of greater than 40 mg tomato lycopene/day. Hadley et al. (2003) reported a significant decrease in lipoprotein oxidizability in healthy elderly subjects, following a 15-day dietary intervention with tomato products. As oxidized lipoproteins have been related to the pathogenesis of CVD, consumption of tomato products may exert a protective effect against oxidative stress in healthy elderly adults.
LDL oxidation has been shown to be reduced by paraoxonase (PON), an enzyme bound to high-density lipoprotein (HDL) and may therefore attenuate the development of atherosclerosis. A recently reported study by Bub et al. (2005) involving a 2-week supplementation of tomato juice (37 mg of lycopene/day), showed a reduced lipid peroxidation in healthy men carrying the R-allele of the PON1-192 genotype, compared to QQ subjects. These volunteers with the QR/RR genotype also showed an increased lipid peroxidation at baseline as compared to QQ subjects. These studies reveal that the dose and duration of tomato lycopene supplementation, the synergistic action of lycopene with natural carotenoids, the baseline plasma levels of lycopene, the choice of biomarkers of oxidative stress and gene polymorphisms affecting the rate of oxidative stress are critical factors in modulating the response to antioxidant supplementation, containing lycopene, in healthy volunteers.
Few studies have been reported on the effects of tomato or lycopene supplementation on oxidative stress-associated diseases. Upritchard et al. (2000) showed a protective effect of 500 ml/day of tomato juice consumption on lipoprotein oxidation (42% increase in LDL lag time) in well-controlled type II diabetic patients.
This study also confirms the synergy among tomato antioxidants, including lycopene, in reducing lipid peroxidation, as reported by in vitro data (Fuhrman et al., 2000). As patients with type II diabetes are at an increased risk of developing coronary heart disease, and oxidized LDLs have been shown to contribute to this risk of arterial disease (Libby, 2006), tomato product supplementation maybe of potential benefit in these patients. Tomato lycopene consumption in patients before prostatectomy has been reported in few studies to lower prostate DNA oxidative damage, serum prostate-specific antigen, and cause an overall reduction in disease aggressiveness (Chen et al., 2001; Kucuk et al., 2001, 2002; Bowen et al., 2002; Table 1). Tomato product or purified lycopene supplementation has previously been shown to decrease oxidative damage in cellular DNA in healthy volunteers (Riso et al., 1999, 2004; Porrini and Riso, 2000; Porrini et al., 2002, 2005; Zhao et al., 2006; Table 1). Although purified lycopene has not been tested in prostate cancer patients, the substantial amount of lycopene accumulating in the prostate tissue in these patients, as reported by the clinical studies, may partially explain the role of lycopene per se in the reduction of prostate DNA damage and biomarkers of prostate carcinogenesis. However, further clinical trials with lycopene alone will determine its prostate-specific anticarcinogenic effects, versus those with tomato products, and may then indicate the possible use of lycopene as complementary therapy for prostate cancer and other types of cancer.
Epidemiologic studies: lycopene, CVD and cancer
A systematic review of 72 epidemiological studies reported a consistent inverse relationship between intakes of tomatoes and plasma lycopene levels and prostate, lung and stomach cancer (Giovannucci, 1999). In the meta-analysis, 10 out of 14 studies reported a significant inverse association between tomato or lycopene consumption and lung cancer risk. These were case–control studies, adjusted for smoking history, an important confounding factor for lung cancer (Giovannucci, 1999). In the Health Professionals Follow-Up Study, an intake of ⩾2 servings a week of tomato products resulted in a lower risk of prostate cancer (Giovannucci et al., 2002). Using plasma samples from men enrolled in the Physicians' Health Study, lycopene was found to be the only antioxidant at significantly lower levels in prostate cancer cases than in the matched controls. This inverse association was particularly evident for aggressive types of prostate cancer and for men not taking a β-carotene supplement (Gann et al., 1999). Several epidemiologic studies have also reported an inverse association between tomato intake and the risk of gastric cancer (La Vecchia et al., 1987; Buiatti et al., 1989; Hansson et al., 1993).
Epidemiological observations also report an inverse association between plasma or tissue lycopene levels and the incidence of CVD. In the Kuopio Ischemic Heart Disease Risk Factor Study, lower levels of plasma lycopene were seen in men who had a coronary event compared with men who did not. In addition, a higher concentration of serum lycopene was inversely correlated with a decrease in the mean and maximal intima-mediated thickness of the common carotid artery (CCA-IMT) with low lycopene, resulting in an 18% increase in CCA-IMT (Rissanen et al., 2003). The European Multicenter Case–Control Study on Antioxidants, Myocardial Infarction and Breast Cancer Study (EURAMIC Study) reported that a higher lycopene concentration was independently protective against CVD (Kohlmeier et al., 1997). The Women's Health Study, further revealed that a decreased risk for developing CVD was more strongly associated with higher tomato intake than with lycopene intake (Sesso et al., 2003).
Processed tomato products definitely provide a bioavailable source of lycopene and have a positive correlation with plasma and tissue lycopene levels. However, these studies do not suggest a role of lycopene per se, in reducing the risks for cancer and CVD, as plasma level of lycopene, in epidemiologic studies, only reflects the consumption of tomatoes and tomato products.
Thus, it can be concluded that moderate amounts of whole food-based supplementation (2–4 servings) of tomato soup, tomato puree, tomato paste, tomato juice or other tomato beverages, consumed with dietary fats, such as olive oil or avocados, leads to increases in plasma carotenoids, particularly lycopene. The recommended daily intake of lycopene has been set at 35 mg that can be obtained by consuming two glasses of tomato juice or through a combination of tomato products (Rao and Agarwal, 2000). These foods may have both chemopreventive as well as chemotherapeutic values as outlined in Figure 1. In the light of recent clinical trials, a combination of naturally occurring carotenoids, including lycopene, in food sources and supplements, is a better approach to disease prevention and therapy, versus a single nutrient. Lycopene has shown distinct antioxidant and anticarcinogenic effects at cellular levels, and definitely contributes to the health benefits of consumption of tomato products. However, until further research establishes significant health benefits of lycopene supplementation per se, in humans, the conclusion may be drawn that consumption of naturally occurring carotenoid-rich fruits and vegetables, particularly processed tomato products containing lycopene, should be encouraged, with positive implications in health and disease.
Agarwal S, Rao AV (1998). Tomato lycopene and low density lipoprotein oxidation: a human dietary intervention study. Lipids 33, 981–984.
Balestrieri ML, Prisco RD, Nicolaus B, Pari P, Moriello VS, Strazzullo G et al. (2004). Lycopene in association with α-tocopherol or tomato lipophilic extracts enhances acyl-platelet-activating factor biosynthesis in endothelial cells during oxidative stress. Free Radical Biol Med 36, 1058–1067.
Boileau AC, Merchen NR, Wasson K, Atkinson CA, Erdman JW (1999). cis-Lycopene is more bioavailable than trans-lycopene in vitro and in vivo in lymph-cannulated ferrets. J Nutr 129, 1176–1181.
Boileau TWM, Boileau AC, Erdman JW (2002). Bioavailability of all-trans and cis-isomers of lycopene. Exp Biol Med 227, 914–919.
Boileau TWM, Liao Z, Kim S, Lemeshow S, Erdman Jr JW, Clinton SK (2003). Prostate carcinogenesis in N-methyl-N-nitrosourea (NMU)-testosterone-treated rats fed tomato powder, lycopene, or energy-restricted diets. J Natl Cancer Inst 95, 1578–1586.
Bowen P, Chen L, Stacewicz-Sapuntzakis M, Duncan C, Sharifi R, Ghosh L et al. (2002). Tomato sauce supplementation and prostate cancer: lycopene accumulation and modulation of biomarkers of carcinogenesis. Exp Biol Med 227, 886–893.
Britton G (1995). Structure and properties of carotenoids in relation to function. FASEB J 9, 1551–1558.
Briviba K, Schnabele K, Rechkemmer G, Bub A (2004). Supplementation of a diet low in carotenoids with tomato or carrot juice does not affect lipid peroxidation in plasma and feces of healthy men. J Nutr 134, 1081–1083.
Bub A, Watzl B, Abrahamse L, Delincee H, Adam S, Wever J et al. (2000). Moderate intervention with carotenoid-rich vegetable products reduces lipid peroxidation in men. J Nutr 130, 2200–2206.
Bub A, Barth SW, Watzl B, Briviba K, Rechkemmer G (2005). Paraoxonase 1 Q192R (PON1-192) polymorphism is associated with reduced lipid peroxidation in healthy young men on a low-carotenoid diet supplemented with tomato juice. Br J Nutr 93, 291–297.
Buiatti E, Palli D, Decarli A, Amadori D, Avellini C, Bianchi S (1989). A case–control study of gastric cancer and diet in Italy. Int J Cancer 44, 611–616.
Canene-Adams K, Campbell JK, Zaripheh S, Jeffery EH, Erdman JW (2005). The tomato as a functional food. J Nutr 135, 1226–1230.
Chen L, Stacewicz-Sapuntzakis M, Duncan C, Sharifi R, Ghosh L, van Breemen R et al. (2001). Oxidative DNA damage in prostate cancer patients consuming tomato sauce-based entrees as a whole-food intervention. J Natl Cancer Inst 93, 1872–1879.
Chopra M, O'Neill ME, Keogh N, Wortley G, Southon S, Thurnham DI (2000). Influence of increased fruit and vegetable intake on plasma and lipoprotein carotenoids and LDL oxidation in smokers and nonsmokers. Clin Chem 46, 1818–1829.
Clinton SK, Emenhiser C, Schwartz SJ, Bostwick DG, Williams AW, Moore BJ et al. (1996). cis–trans lycopene isomers, carotenoids, and retinol in the human prostate. Cancer Epidemiol Biomarkers Prev 5, 823–833.
de Lorgeril M, Salen P, Martin JL, Monjaud I, Delaye J, Mamelle N (1999). Mediterranean Diet, Traditional Risk Factors, and the Rate of Cardiovascular Complications After Myocardial Infarction: Final Report of the Lyon Diet Heart Study. Circulation 99, 779–785.
Di Mascio P, Kaiser S, Sies H (1989). Lycopene as the most efficient biological carotenoid singlet oxygen quencher. Arch Biochem Biophys 274, 532–538.
Diwadkar-Navsariwala V, Novotny JA, Gustin DM, Sosman JA, Rodvold KA, Crowell JA et al. (2003). A physiological pharmacokinetic model describing the disposition of lycopene in healthy men. J Lipid Res 44, 1927–1939.
Fuhrman B, Elis A, Aviram M (1997). Hypocholesterolemic effect of lycopene and β-carotene is related to suppression of cholesterol synthesis and augmentation of LDL receptor activity in macrophages. Biochem Biophys Res Commun 233, 658–662.
Fuhrman B, Volkova N, Rosenblat M, Aviram M (2000). Lycopene synergistically inhibits LDL oxidation in combination with vitamin E, glabridin, rosmarinic acid, carnosic acid, or garlic. Antioxidants Redox Signal 2, 491–506.
Gann PH, Ma J, Giovannucci E, Willett W, Sacks FM, Hennekens CH et al. (1999). Lower prostate cancer risk in men with elevated plasma lycopene levels: results of a prospective analysis. Cancer Res 59, 1225–1230.
Gartner C, Stahl W, Sies H (1997). Lycopene is more bioavailable from tomato paste than from fresh tomatoes. Am J Clin Nutr 66, 116–122.
Giovannucci E (1999). Tomatoes, tomato-based products, lycopene, and cancer: review of the epidemiologic literature. J Natl Cancer Inst 91, 317–331.
Giovannucci E, Rimm E, Liu Y, Stampfer M, Willett W (2002). A prospective study of tomato products, lycopene, and prostate cancer risk. J Natl Cancer Inst 94, 391–398.
Hadley CW, Clinton SK, Schwartz SJ (2003). The consumption of processed tomato products enhances plasma lycopene concentrations in association with a reduced lipoprotein sensitivity to oxidative damage. J Nutr 133, 727–732.
Hansson LE, Nyren O, Bergstrom R, Wolk A, Lindgren A, Baron J et al. (1993). Diet and risk of gastric cancer. A population-based case-control study in Sweden. Int J Cancer 55, 181–189.
Hantz HL, Young LF, Martin KR (2005). Physiologically attainable concentrations of lycopene induce mitochondrial apoptosis in LNCaP human prostate cancer cells. Exp Biol Med 230, 171–179.
Hininger IA, Meyer-Wenger A, Moser U, Wright A, Southon S, Thurnham D et al. (2001). No significant effects of lutein, lycopene or β-carotene supplementation on biological markers of oxidative stress and LDL oxidizability in healthy adult subjects. J Am Coll Nutr 20, 232–238.
Holloway DE, Yang M, Paganga G, Rice-Evans CA, Bramley PM (2000). Isomerization of dietary lycopene during assimilation and transport in plasma. Free Radical Res 32, 93–102.
Hoppe PP, Kramer K, van den Berg H, Steenge G, van Vliet T (2003). Synthetic and tomato-based lycopene have identical bioavailability in humans. Eur J Nutr 42, 272–278.
Hwang E-S, Bowen PE (2005). Effects of lycopene and tomato paste extracts on DNA and lipid oxidation in LNCaP human prostate cancer cells. Biofactors 23, 97–105.
Karas M, Amir H, Fishman D, Danilenko M, Segal S, Nahum A et al. (2000). Lycopene interferes with cell cycle progression and insulin-like growth factor I signaling in mammary cancer cells. Nutr Cancer 36, 101–111.
Kiokias S, Gordon MH (2003). Dietary supplementation with a natural carotenoid mixture decreases oxidative stress. Eur J Clin Nutr 57, 1135–1140.
Kohlmeier L, Kark JD, Gomez-Gracia E, Martin BC, Steck SE, Kardinaal AF et al. (1997). Lycopene and myocardial infarction risk in the EURAMIC Study. Am J Epidemiol 146, 618–662.
Kucuk O, Sarkar FH, Sakr W, Djurie Z, Pollak MN, Khachik F et al. (2001). Phase II randomized clinical trial of lycopene supplementation before radical prostatectomy. Cancer Epidemiol Biomarkers Prev 10, 861–868.
Kucuk O, Sarkar FH, Djuric Z, Sakr W, Pollak MN, Khachik F et al. (2002). Effects of lycopene supplementation in patients with localized prostate cancer. Exp Biol Med 227, 881–885.
La Vecchia C (1997). Mediterranean epidemiological evidence on tomatoes and the prevention of digestive tract cancers. Proc Soc Exp Biol Med 218, 125–128.
La Vecchia C, Negri E, Decarli A, D'Avanzo B, Franceschi S (1987). A case control study of diet and gastric cancer in northern Italy. Int J Cancer 40, 484–489.
Lee A, Thurnham D, Chopra M (2000). Consumption of tomato products with olive oil but not sunflower oil increases the antioxidant activity of plasma. Free Radical Biol Med 29, 1051–1055.
Levin G, Yeshurun M, Mokady S (1997). In vivo antiperoxidative effect of 9-cis β-carotene compared with that of the all-trans isomer. Nutr Cancer 27, 293–297.
Libby P (2006). Inflammation and cardiovascular disease mechanisms. Am J Clin Nutr 83, 456S–460S.
Liu C, Russell RM, Wang X-D (2006). Lycopene supplementation prevents smoke-induced changes in p53, p53 phosphorylation, cell proliferation, and apoptosis in the gastric mucosa of ferrets. J Nutr 136, 106–111.
Obermuller-Jevic UC, Olano-Martin E, Corbacho AM, Eiserich JP, van der Vliet A, Valacchi G et al. (2003). Lycopene inhibits the growth of normal human prostate epithelial cells in vitro. J Nutr 133, 3356–3360.
Pool-Zobel BL, Bub A, Muller H, Wollowski I, Rechkemmer G (1997). Consumption of vegetables reduces genetic damage in humans: first result of a human intervention trial with carotenoid-rich foods. Carcinogenesis 18, 1847–1850.
Porrini M, Riso P, Testolin G (1998). Absorption of lycopene from single or daily portions of raw and processed tomato. Br J Nutr 80, 353–361.
Porrini M, Riso P (2000). Lymphocyte lycopene concentration and DNA protection from oxidative damage is increased in women after a short period of tomato consumption 130, 189–192.
Porrini M, Riso P, Oriani G (2002). Spinach and tomato consumption increases lymphocyte DNA resistance to oxidative stress but this is not related to cell carotenoid concentrations. Eur J Nutr 41, 95–100.
Porrini M, Riso P, Brusamolino A, Berti C, Guarnieri S, Visioli F (2005). Daily intake of a formulated tomato drink affects carotenoid plasma and lymphocyte concentrations and improves cellular antioxidant protection. Br J Nutr 93, 93–99.
Rao AV, Agarwal S (1998). Bioavailability and in vivo antioxidant properties of lycopene from tomato products and their possible role in the prevention of cancer. Nutr Cancer 31, 199–203.
Rao AV, Agarwal S (2000). Role of antioxidant lycopene in cancer and heart disease. J Am Coll Nutr 19, 563–569.
Rao AV (2002). Lycopene, tomatoes, and the prevention of coronary heart disease. Exp Biol Med 227, 908–913.
Rao AV, Shen H (2002). Effect of low dose lycopene intake on lycopene bioavailability and oxidative stress. Nutr Res 22, 1125–1131.
Rao AV (2004). Processed tomato products as a source of dietary lycopene: bioavailability and antioxidant properties. Can J Diet Pract Res 65, 161–165.
Reboul E, Borel P, Mikail C, Abou L, Charbonnier M, Caris-Veyrat C et al. (2005). Enrichment of tomato paste with 6% tomato peel increases lycopene and β-carotene bioavailability in men. J Nutr 135, 790–794.
Re R, Fraser PD, Long M, Bramley PM, Rice-Evans C (2001). Isomerization of lycopene in the gastric milieu. Biochem Biophys Res Commun 281, 576–581.
Richelle M, Bortlik K, Liardet S, Hager C, Lambelet P, Baur M et al. (2002). A food-based formulation provides lycopene with the same bioavailability to humans as that from tomato paste. J Nutr 132, 404–408.
Riso P, Pinder A, Santangelo A, Porrini M (1999). Does tomato consumption effectively increase the resistance of lymphocyte DNA to oxidative damage? Am J Clin Nutr 69, 712–718.
Riso P, Visioli F, Erba D, Testolin G, Porrini M (2004). Lycopene and vitamin C concentrations increased in plasma and lymphocytes after tomato intake. Effects on cellular antioxidant protection. Eur J Clin Nutr 58, 1350–1358.
Rissanen T, Voutilainen S, Nyyssonen K, Salonon J, Kaplan G, Salonen J (2003). Serum lycopene concentration and carotid atherosclerosis: the Kuopio Ischemic Heart Disease Risk Factor Study. Am J Clin Nutr 77, 133–138.
Sesso HD, Liu S, Gaziano JM, Buring JE (2003). Dietary lycopene, tomato-based food products and cardiovascular disease in women. J Nutr 133, 2336–2341.
Siler U, Barella L, Spitzer V, Schnorr J, Lein M, Goralczyk R et al. (2004). Lycopene and vitamin E interfere with autocrine/paracrine loops in the Dunning prostate cancer model. FASEB J (published online April 14, 2004).
Stahl W, von Laar J, Martin HD, Emmerich T, Sies H (2000). Stimulation of gap junctional communication: comparison of acyclo-retinoic acid and lycopene. Arch Biochem Biophys 373, 271–274.
Unlu NZ, Bohn T, Clinton SK, Schwartz SJ (2005). Carotenoid absorption from salad and salsa by humans is enhanced by the addition of avocado or avocado oil. J Nutr 135, 431–436.
Upritchard JE, Sutherland WHF, Mann JI (2000). Effect of supplementation with tomato juice, vitamin E, and vitamin C on LDL oxidation and products of inflammatory activity in Type 2 diabetes. Diabetes Care 23, 733–738.
Vine AL, Bertram JS (2005). Upregulation of connexin 43 by retinoids but not by non- provitamin A carotenoids requires RARs. Nutr Cancer 52, 105–113.
Visioli F, Riso P, Grande S, Galli C, Porrini M (2003). Protective activity of tomato products on in vivo markers of lipid oxidation. Eur J Nutr 42, 201–206.
Wu K, Schwartz SJ, Platz EA, Clinton SK, Erdman JW, Ferruzzi MG et al. (2003). Variations in plasma lycopene and specific isomers over time in a cohort of US men. J Nutr 133, 1930–1936.
Zhao X, Aldini G, Johnson EJ, Rasmussen H, Kraemer K, Woolf H et al. (2006). Modification of lymphocyte DNA damage by carotenoid supplementation in postmenopausal women. Am J Clin Nutr 83, 163–169.
About this article
Cite this article
Basu, A., Imrhan, V. Tomatoes versus lycopene in oxidative stress and carcinogenesis: conclusions from clinical trials. Eur J Clin Nutr 61, 295–303 (2007). https://doi.org/10.1038/sj.ejcn.1602510
- oxidative stress
- prostate cancer
Effect of tomato, lycopene and related products on blood pressure: A systematic review and network meta-analysis
Drying Technology (2021)
Tomato powder is more effective than lycopene to alleviate exercise-induced lipid peroxidation in well-trained male athletes: randomized, double-blinded cross-over study
Journal of the International Society of Sports Nutrition (2021)
Effect of Irrigation Water Containing Iodine on Plant Physiological Processes and Elemental Concentrations of Cabbage (Brassica oleracea L. var. capitata L.) and Tomato (Solanum lycopersicum L.) Cultivated in Different Soils
Journal on Processing and Energy in Agriculture (2020)