Tomato (Solanum lycopersicum): A Comprehensive Reference
1. Identity
Botanical and Chemical Classification
The tomato (Solanum lycopersicum) is a dicotyledonous plant belonging to the family Solanaceae, with a perennial vegetative cycle, although it is grown annually. Once categorized under Lycopersicon esculentum, modern genetic research has reclassified it into the Solanum genus, aligning it with other nightshades like potatoes and eggplants. The CAS Number for tomato extract reference is 90131-63-8. Synonyms include Solanum lycopersicum, Lycopersicon esculentum (former botanical name), Tomato, Garden Tomato, Lycopersicum Fruit, Tomato Powder, Tomato Pulp, Tomato Juice, Tomato Seed Oil, and numerous cultivar designations such as Cherry Tomato, Plum Tomato, Roma Tomato, and Beefsteak Tomato.
Botanically classified as a fruit yet often treated as a vegetable in cooking contexts, tomatoes defy easy categorization. Tomato (Solanum lycopersicum) is the largest produced vegetable crop in the world after potato and sweet potato.
Natural Source and Geographic Origin
It is a native fruit from the Andean region comprising Chile, Bolivia, Colombia, and Peru, which then spread to Central America and from there to Europe. While the tomato's wild ancestors grow in Chile, Peru, and Ecuador, the fruit was domesticated by precontact Central American farmers. The exact date of domestication is unknown; by 500 BCE, it was already being cultivated in southern Mexico and probably other areas.
Common Forms and Preparations
Solanum lycopersicum is grown worldwide for fresh consumption and as a raw material for processed food products such as sauces, pastes, and juices. As a dietary supplement or functional ingredient, tomato-derived preparations include tomato powder, tomato extract (oleoresin), lycopene isolate (synthetic or natural), tomato paste concentrate, and softgel capsules containing tomato nutrient complex (TNC) or purified lycopene. 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.
2. Traditional and Historical Use
Mesoamerican Origins
The Aztecs raised several varieties of tomato, with red tomatoes called xitomatl. In the Aztec language of Nahuatl, tomatoes were known as tomatl, which has been translated as "plump fruit with navel." The Spanish were likely first introduced to this fruit sometime between 1519 and 1521, when the Spanish conquistador Hernán Cortés invaded the Aztec capital of Tenochtitlán (present-day Mexico City).
The wild tomato was domesticated by the indigenous peoples of Mesoamerica, especially the Aztecs, who called it tomatl. They used tomatoes in their cooking, medicine, and rituals. They also developed different varieties of tomatoes, such as red, yellow, and striped ones. Aztec writings include recipes containing peppers, tomatoes, and seasoning — an early salsa recipe.
Bernardino de Sahagún reported seeing a great variety of tomatoes in the Aztec market at Tenochtitlán (Mexico City): "large tomatoes, small tomatoes, leaf tomatoes, sweet tomatoes, large serpent tomatoes, nipple-shaped tomatoes," and described Aztecs cooking various sauces with tomatoes of different sizes, serving them in city markets.
Introduction to Europe
The Aztec taught the Spanish several ways to prepare tomatoes including cooked or mixed with peppers. The tomato was cultivated in Europe only a few years after the conquest of Tenochtitlán, by the 1540s, and grew easily in the Mediterranean climates. The earliest mention of the tomato in European literature appeared in Pietro Andrea Mattioli's 1544 herbal, where he suggested that a new type of eggplant had been brought to Italy.
By the mid-1500s, European nobles, many of whom fancied themselves amateur naturalists, planted tomatoes in their gardens along with other exotic species. The tomato at this time was largely used as an ornamental plant. While the Spanish knew that the Aztecs consumed tomatoes, Europeans initially greeted the fruit with suspicion — largely due to its being a member of the nightshade family, which was known to include a number of toxic plants. Moreover, early on, some Europeans did experiment with eating tomatoes and reportedly became ill after eating them, reinforcing the fears that tomatoes were poisonous.
The tomato's Latin name, Solanum lycopersicum, reflects that it was originally named "wolf peach" by suspicious Europeans. They thought it was poisonous and originally grew it as an ornamental climber. The Spanish first introduced tomatoes to Europe, where they became used in Spanish food. Tomatoes only gradually gained acceptance as an edible food across wider Europe over the course of the 16th and 17th centuries.
3. Key Constituents and Active Compounds
Carotenoids
Tomatoes and tomato-based food products are the main sources of lycopene and carotenoids, such as phytoene, phytofluene, α-carotene, β-carotene, γ-carotene, and neurosporene, which together with vitamin C, potassium, and folic acid turn the tomato into a fruit with beneficial properties for human health.
Lycopene is the most pharmacologically studied compound in tomato. Lycopene is chemically an acyclic carotene with 11 conjugated double bonds, normally in trans configuration, while isomerization occurs in blood plasma for better absorption. Tomato (Solanum lycopersicum) is one of the most essential herbaceous plants that have been probed against various life-related disorders owing to an array of phytochemicals. Lycopene is one of the most potent antioxidants among dietary carotenoids.
Tomato also contains other active carotenoid compounds, namely neoxanthin, lutein, α-cryptoxanthin, α-carotene, β-carotene, cyclolycopene, and β-carotene 5,6-epoxide.
Polyphenols and Phenolic Acids
Tomato and its products are valuable sources of polyphenols, including naringenin chalcone, rutin, quercetin, chlorogenic acid, caffeic acid, naringenin, kaempferol-3-rutinoside, p-coumaric acid, ferulic acid, and kaempferol, which have been reported to have some positive health effects such as reducing the risk of chronic diseases, including cancer, especially prostate cancer, and cardiovascular diseases.
The phenolic compounds reported in tomato are phenolic acids (caffeic, chlorogenic, sinapic, p-coumaric, and ferulic acids) and flavonoids (quercetin, rutin, kaempferol, and naringenin). Quercetin, the most abundant flavonoid, was found in concentrations ranging between 7.19 and 43.59 mg/kg fresh weight in commercial varieties, while the most abundant hydroxycinnamic acid was chlorogenic acid, with values ranging from 14 to 32 mg/kg fresh weight.
Chlorogenic acid is an important and biologically active dietary polyphenol, which plays several therapeutic roles as antioxidant, anti-inflammatory, hepatoprotective, cardioprotective, hypoglycemic, antimicrobial, and antiviral agent.
Vitamins and Minerals
Tomato is an important source of vitamin C, potassium, folic acid, and carotenoids, such as lycopene. Its nutritional composition is notably high in vitamins A, C, K, potassium, and lycopene.
Other Bioactives
Tomato is a good source of phenolic compounds (phenolic acids and flavonoids), carotenoids (lycopene, α- and β-carotene), vitamins (ascorbic acid and vitamin A), and glycoalkaloids (tomatine). Bioactive constituents present in tomato have antioxidant, anti-mutagenic, anti-proliferative, anti-inflammatory, and anti-atherogenic activities.
4. Established Mechanisms of Action
Antioxidant Activity
Lycopene is characterized by a high antioxidant potential, the highest among carotenoid pigments. Lycopene can scavenge reactive oxygen species (ROS) and nitrogen species (RNS) at a dose range from 0.31 to 10 μM, significantly reducing DNA damage in the comet assay. Lycopene also modulates production of the antioxidant enzymes superoxide dismutase and catalase.
Anti-Inflammatory Pathways
Lycopene's anti-inflammatory mechanisms include the inhibition of pivotal pro-inflammatory mediators, such as the reduction of reactive oxygen species, the inhibition of synthesis and release of pro-inflammatory cytokines, changes in the expression of cyclooxygenase and lipoxygenase, modifications of eicosanoid synthesis, and modulation of signal transduction pathways, including that of the inducible nitric oxide synthase via its inhibitory effects on Nuclear Factor-κB (NF-κB), Activated protein-1 (AP-1), and mitogen-activated protein kinase (MAPK) signaling. Recent data suggest that lycopene also exhibits anti-inflammatory activity through induction of programmed cell death in activated immune cells.
Cardiovascular Mechanisms
Mechanistically, lycopene's cardiovascular benefits may be mediated through multiple pathways, including the prevention of low-density lipoprotein (LDL) oxidation, inhibition of NF-κB-mediated inflammatory responses, and modulation of lipid metabolism via nuclear hormone receptor signaling. Lycopene reduces blood pressure via inhibiting the angiotensin-converting enzyme and regulating nitrous oxide bioavailability. Lycopene also inhibits HMG-CoA reductase, the same enzyme targeted by statin drugs for cholesterol reduction, and enhances endothelial function by promoting nitric oxide bioavailability.
Anticancer Mechanisms
The reported mechanisms of lycopene action in vivo include regulation of oxidative and inflammatory processes, induction of apoptosis, and inhibition of cell division, angiogenesis, and metastasis formation. Lycopene has the ability for adenosine deaminase inhibition, which plays an important role in the regression of tumors.
Bone-Related Mechanisms
Lycopene activates the WNT/β-catenin and ERK1/2 pathways, upregulates RUNX2, alkaline phosphatase, and COL1A, and downregulates RANKL in osteoblast cells. These pathways are critical for osteoblast differentiation and bone matrix formation.
5. Scientific Evidence by Area of Use
5.1 Cancer — Prostate Cancer
Prostate cancer is the most extensively studied area for tomato and lycopene. Dietary intake of tomatoes and tomato products containing lycopene has been shown to be associated with a decreased risk of chronic diseases, such as cancer and cardiovascular disease. Serum and tissue lycopene levels have been found to be inversely related to the incidence of several types of cancer, including breast cancer and prostate cancer.
A reduction in risk of almost 35% was observed for a consumption frequency of 10 or more servings of tomato products per week, and the protective effects were even stronger with more advanced or aggressive prostate cancer in a landmark epidemiological cohort study. In 2014, a high-quality 24-year follow-up nested case-control study including 51,529 US healthy men suggested a reduced odds of prostate cancer for those with highest lycopene intake when compared to those with lowest lycopene intake (hazard ratio [HR] 0.91, 95% CI 0.84 to 1.00).
Despite these observational associations, the interventional clinical evidence is limited. Given that only three RCTs were included in one Cochrane systematic review, and the high risk of bias in two of the three studies, there is insufficient evidence to either support, or refute, the use of lycopene for the prevention of prostate cancer. Though there is considerable interest in lycopene as a therapeutic agent, only a few high-quality studies have been reported analyzing its effect on prostate cancer. A 2012 systematic review identified only four randomized controlled clinical studies that tested lycopene as a therapeutic agent for prostate cancer. Recent systematic reviews could show that lycopene is able to decrease serum PSA levels in patients with prostate hyperplasia or cancer, demonstrating its effect on proliferating prostate cells. However, there is still no clearly proven clinical evidence supporting the use of lycopene in the prevention or treatment of prostate cancer, due to the limited number of available RCTs.
Although no statistical significance was found in one meta-analysis, higher lycopene intake showed a trend to reduce the incidence of prostate cancer. According to the latest Continuous Update Project report summarized by the World Cancer Research Fund in 2014, there is limited evidence for the effect of lycopene on prostate cancer risk.
Evidence strength: Preliminary to moderate for observational associations; insufficient RCT evidence to confirm causality or support clinical recommendations.
5.2 Cancer — Other Types
A systematic review examining benefits of lycopene supplementation in cancer prevention and treatment based on in vivo studies identified 72 human and animal studies analyzed for endpoints such as cancer incidence, improvement in treatment outcomes, and mechanisms of lycopene action. The reviewers concluded that the results of most of the reviewed in vivo studies confirmed the anti-cancer activities of lycopene. Most of the studies concerned prostate cancer, reflecting the number of in vitro studies.
There is limited in vivo data on the health benefits of lycopene alone. Most 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.
Evidence strength: Preliminary; mostly in vitro and animal evidence, with limited and inconsistent human RCT data for cancer types other than prostate.
5.3 Cardiovascular Disease
Growing evidence supports lycopene's beneficial role for the heart, endothelium, blood vessels, and health. It is generally accepted that consuming one or more servings of lycopene-rich tomato products per day is associated with less than a 30% risk of cardiovascular disease.
Blood Pressure: In 3 of 5 lycopene supplement studies, lycopene at 15 mg/day for 6–8 weeks decreased systolic blood pressure and diastolic blood pressure. The benefits were apparent in individuals with stage 1 hypertension who were otherwise healthy. Two other studies reported no differences in blood pressure after lycopene supplementation at similar doses and duration.
A recent umbrella review of systematic reviews and meta-analyses confirmed that lycopene intake from tomatoes significantly improves blood pressure indices. Although these reductions are modest (approximately 2–3 mmHg for systolic blood pressure), they have meaningful clinical implications. Meta-analyses of large-scale trials have demonstrated that every 5 mmHg reduction in systolic blood pressure is associated with an approximately 10% lower risk of major cardiovascular events.
LDL and Lipid Profiles: Studies indicated that consuming tomatoes and tomato products containing lycopene reduced the risk of cardiovascular disease, partly through protection against oxidation of low-density lipoproteins. However, lycopene supplementation does not significantly prolong the lag time of low-density lipoprotein (mean difference 3.76 [95% CI −2.48, 10.01]; P=.24) in some meta-analyses, reflecting inconsistency across trials.
Inflammation: Results were underwhelming for both tomato products and lycopene supplements on selected inflammatory markers such as CRP. However, the available evidence remains limited and represents an opportunity for future research on the anti-inflammatory activity of tomatoes and lycopene.
Systematic reviews and meta-analyses of cardiovascular effects have often yielded inconsistent results, likely due to variations in their quality, lycopene formulation and dosage, as well as other methodological differences.
Evidence strength: Moderate for blood pressure reduction in hypertensive individuals at 15 mg/day lycopene; mixed/insufficient for lipid and inflammatory markers.
5.4 Skin and Photoprotection
Lycopene is the major carotenoid of the tomato and is a very efficient singlet oxygen quencher in the group of carotenoids. Following ingestion of lycopene or tomato-derived products rich in lycopene, photoprotective effects have been demonstrated. Following consumption, carotenoids are deposited in the skin of humans, where they are present and able to protect from UV damage.
In a notable randomized controlled trial, 20 healthy women ingested 55 g tomato paste (16 mg lycopene) in olive oil, or olive oil alone, daily for 12 weeks. Mean erythemal dose was significantly higher following tomato paste versus control, and tomato paste containing lycopene was found to provide protection against acute and potentially longer-term aspects of photodamage.
In a double-blind, randomized, placebo-controlled crossover study, a lycopene-rich tomato nutrient complex (TNC) completely inhibited UVA1- and UVA/B-induced upregulation of heme-oxygenase 1, intercellular adhesion molecule 1, and matrix metallopeptidase 1 mRNA, regardless of treatment sequence.
A systematic review and meta-analysis (21 eligible studies from 19,336 publications) found that interventions supplementing tomato and lycopene were associated with significant reductions in skin erythema marker (Δa*), MMP-1, ICAM-1, and skin pigmentation, while supplementation was associated with significant increase in minimal erythema dose (MED), skin thickness, and skin density. Supplementation with tomato and lycopene could reduce skin erythema formation and improve the appearance and pigmentation of the skin, thereby preventing light-induced skin photodamage and photoaging.
When comparing lycopene administered from a whole food (tomato) versus a synthesized supplement, tomatoes appear more efficacious in preventing redness after UV exposure, suggesting other phytochemicals in tomatoes may additionally contribute to this effect.
Evidence strength: Moderate; multiple RCTs and a meta-analysis support photoprotective effects of tomato/lycopene supplementation; clinical significance as a stand-alone sun protection measure remains to be fully quantified.
5.5 Bone Health
Lycopene intake could prevent bone loss; however, studies on its effects on bone are scarce. Research has aimed to investigate the effects of lycopene on osteoblast cells as well as bone mineral density and bone turnover markers in postmenopausal women.
In a pilot controlled clinical study involving 39 postmenopausal women consuming a lycopene-rich tomato sauce, a significant bone density loss was not detected in women taking the tomato sauce while the control group had bone loss (p = 0.002). Tomato sauce intake resulted in a greater bone alkaline phosphatase reduction than the control (18% vs 8.5%, p = 0.03).
Evidence strength: Preliminary; based on a small pilot study and in vitro data; larger RCTs are needed before conclusions can be drawn.
5.6 Oxidative Stress
A double-blind, randomized, placebo-controlled trial examined the effects of 8-week supplementation of purified lycopene on biomarkers of oxidative stress in healthy volunteers. This study examined the effects of supplementation at doses of 0, 6.5, 15, or 30 mg lycopene/day for 8 weeks in healthy adults (n = 77, age ≥ 40 years). Results from a meta-analysis indicate that lycopene supplementation significantly decreases the DNA tail length, as determined using comet assays, with a mean difference (MD) of −6.27 [95% CI −10.74, −1.80] (P = .006) between lycopene intervention groups and control groups. While tomato product supplementation containing antioxidant carotenoids, including lycopene, decreases oxidative stress, the role of purified lycopene as an antioxidant remains unclear.
Evidence strength: Moderate for DNA damage reduction; mixed and insufficient for other antioxidant endpoints such as LDL oxidizability in isolation.
6. Body Systems and Health Areas Associated with Tomato
- Oncology/Cancer Prevention: Dietary intake of tomatoes and tomato products has been associated with a decreased risk of chronic diseases such as cancer and cardiovascular disease.
- Cardiovascular System: Lycopene's role in modulating cardiovascular risk factors, such as blood pressure, lipid profiles, blood glucose levels, and endothelial function, has been the focus of numerous clinical trials.
- Integumentary System (Skin): Lycopene-rich products could be used as endogenous sun protection and may be a potential nutraceutical for sun protection.
- Musculoskeletal System (Bone): The cellular mechanisms of lycopene contributed to preventing bone loss in postmenopausal women in pilot research.
- Immune System and Inflammation: Lycopene modulates inflammatory signaling through inhibition of NF-κB, AP-1, and MAPK pathways and reduces pro-inflammatory cytokines.
- Oxidative Stress/General Cellular Protection: Bioactive constituents in tomato have antioxidant, anti-mutagenic, anti-proliferative, anti-inflammatory, and anti-atherogenic activities.
7. Dosage Forms and Dosages Reported in Studies
Lycopene Supplementation Doses Used in Clinical Studies
- Lycopene at 15 mg/day for 6–8 weeks was used in blood pressure studies and decreased systolic and diastolic blood pressure in 3 of 5 studies.
- Healthy adults (n = 77, age ≥ 40 years) were randomized to receive 0, 6.5, 15, or 30 mg lycopene/day for 8 weeks in an oxidative stress study.
- In a 30-day cardiovascular trial in patients with coronary vascular disease, patients were supplemented with a single 7 mg daily dose of lycopene, ingested either in the form of lactolycopene (68 patients) or in the form of lycosome-formulated lycopene (74 patients).
- In a 12-week randomized controlled trial on skin photoprotection, 20 healthy women ingested 55 g tomato paste (16 mg lycopene) in olive oil daily.
- Volunteers in a 12-week photoprotection study ingested similar amounts of lycopene (approximately 10 mg/day) from different sources.
- A phase I trial evaluated lycopene doses of 30, 90, or 150 mg/day in combination with docetaxel in 24 participants with metastatic prostate cancer.
Whole Tomato/Tomato Product Doses
- The consumption of tomato products in amounts of 70–400 g/day for 1–180 days has been studied for cardioprotective effects.
- In a crossover cardiovascular study, participants consumed 300 g of raw cherry tomatoes per day for four weeks.
Lycopene Content in Food
- The highest lycopene concentration in fresh tomato varieties has been measured at 243 ± 7 μg/g.
- Average daily lycopene intake in Europe is highest in Italy (7.4 mg) and lowest in the UK (1.1 mg), with intake reaching up to 20 mg per day in Mediterranean populations.
- No established upper intake limit exists for lycopene, though clinical studies have demonstrated tolerability of supplemental doses up to 75 mg per day.
8. Bioavailability
Lycopene naturally exists in fruits and vegetables in the form of a trans-isomer, which presents a low absorption rate and bioavailability. The bioavailability of lycopene is also influenced by cooking, interactions with other carotenoids, and the presence of fat or oil. Thermal processing of tomato products can cause changes in the structure of lycopene to yield cis-isomers in the product, and this form is more bioavailable.
The predominant all-trans form in raw foods has an estimated absorption rate of only 10–30%, while cis-isomers exhibit higher absorption rates of 40–50%, owing to their greater solubility in bile acid micelles and reduced tendency to crystallize. Dietary fats enhance this process and should be consumed together with food sources of lycopene.
The bioavailability of lycopene varied significantly depending on the administered matrix in comparative bioavailability studies. In studies, lycopene was significantly better available from processed tomatoes compared to raw tomatoes, when using daily intakes between 16.5 mg and 75 mg lycopene.
The cis-isomers of lycopene occurring in tangerine tomatoes were, through clinical trials, proven to be more bioavailable than the all-trans lycopene found in red tomatoes.
9. Safety Considerations and Interactions
General Tolerability
Tomato-based products and lycopene supplements are generally well tolerated. The literature documents some gastrointestinal complaints, such as diarrhea, dyspepsia, gas, nausea, and vomiting. One trial documented a cancer-related hemorrhage in a patient taking lycopene, but causality was unclear. Tomato-based products are acidic and may irritate stomach ulcers.
Lycopenodermia
High dietary or supplemental intake of lycopene can cause lycopenodermia, a benign orange-yellow discoloration of the skin, which is reversible upon discontinuation of high intake. This is analogous to carotenodermia seen with excessive beta-carotene consumption.
Pregnancy and Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking. Clinical studies evaluating the effects of supplemental lycopene in preeclampsia have produced conflicting results regarding benefit, and some evidence of harm has been reported. Amounts typically found in food are considered safe. Tomato consumption increases lycopene concentrations in the breast milk and plasma of lactating women.
Drug and Supplement Interactions
- Calcium supplements: 500 mg of calcium carbonate reduced lycopene absorption by up to 83% when taken concurrently. This is a pharmacokinetic interaction — separation by at least 2 hours is recommended.
- Divalent minerals: Divalent mineral ions from calcium, magnesium, ferrous iron, and zinc supplements can bind carotenoids and reduce bioavailability. Separation from lycopene by at least 2 hours is advised.
- Alcohol: High doses of lycopene supplementation (3.3 mg/kg/day, the equivalent dose to 45 mg/day in humans) combined with chronic alcohol ingestion can induce the expression of cytochrome CYP2E1 and may promote the harmful effects of excessive alcohol intake.
- HMG-CoA reductase inhibitors (statins): Lycopene inhibits HMG-CoA reductase, the same enzyme targeted by statin drugs for cholesterol reduction, which suggests a potential pharmacodynamic overlap; the clinical significance of this interaction has not been established in RCTs.
FDA Qualified Health Claims
The U.S. Food and Drug Administration has reviewed evidence for qualified health claims regarding tomatoes, lycopene, and cancer risk. The FDA's conclusion, based on a systematic evidence review, was that the evidence was limited and inconsistent, and no authoritative health claim could be supported for lycopene and cancer risk reduction at the time of review.
Evidence Quality Summary
Although the antioxidant properties of lycopene are thought to be primarily responsible for its beneficial effects, evidence is accumulating to suggest that other mechanisms may also be involved. The health effects of tomato have been mainly associated with carotenoids, and there are a limited number of studies on tomato polyphenols. Epidemiologic evidence and dietary intervention studies have associated tomato and lycopene with lower incidence rates of cardiovascular diseases and cancers; however, the effect of lycopene supplementation alone remains unconfirmed. Across most areas, the strongest evidence supports tomato as a whole-food matrix rather than isolated lycopene as a supplement, and synergistic interactions among multiple bioactive constituents are likely important.
References
Volver