Tomatoes are generally compatible with gout: they contain approximately 11 mg of purines per 100 g, a content well below the threshold of foods considered problematic (above 150 mg/100 g). However, studies published between 2012 and 2015 highlighted a paradox: tomatoes can trigger gout attacks in certain patients despite their low purine content, due to an independent mechanism involving glutamine and glutamic acid.
Gout is an inflammatory joint disease caused by hyperuricemia (blood uric acid levels above 360 µmol/L in women and 420 µmol/L in men), leading to the deposition of monosodium urate crystals in the joints. Dietary management is an essential pillar of attack prevention, and the question of tomatoes perfectly illustrates the complexity of this approach: a food can be low in purines and yet influence uric acid levels through other biological pathways. Understanding these mechanisms allows for a more informed and personalized dietary approach.
What is the purine content of tomatoes?
Tomatoes contain approximately 11 mg of purines per 100 g according to data from the USDA (United States Department of Agriculture) nutritional database, placing them among foods with very low purine content. By comparison, organ meats such as calf liver reach 250 to 300 mg/100 g, and anchovies exceed 400 mg/100 g.
Purines are nitrogen-containing organic compounds naturally present in living cells, which are broken down into uric acid during digestion and cellular metabolism. The richer a food is in purines, the more likely its consumption is to raise uricemia (the level of uric acid in the blood). Tomatoes, with their 11 mg/100 g, therefore do not constitute a significant source of purines in theoretical terms.
| Food | Purine content (mg/100 g) | Gout risk level |
|---|---|---|
| Fresh tomato | 11 | Very low |
| Chicken (breast) | 175 | Moderate |
| Canned sardines | 345 | High |
| Anchovies | 411 | Very high |
| Calf liver | 260 | Very high |
| Cooked lentils | 70 | Low |
| Raw spinach | 57 | Low |
| Beer (330 ml) | 15–20 | High (fructose + alcohol) |
Source: USDA Nutritional Database (FoodData Central).
Why can tomatoes trigger a gout attack despite their low purine content?
Tomatoes can cause an increase in uric acid through a mechanism independent of purines, involving the glutamine and glutamic acid they contain, according to a cohort study published in 2015 in the journal BMC Musculoskeletal Disorders (Abhishek et al., 2015). This discovery surprised the medical community and calls into question the purely purine-centered approach.
The mechanism of glutamine and glutamic acid
Tomatoes are relatively rich in glutamine and glutamic acid, two non-essential amino acids. In certain genetically predisposed patients, these amino acids may be metabolized in a way that stimulates endogenous uric acid production or reduces its renal elimination. This phenomenon is still under study, but it explains why tomatoes appear among the self-reported trigger foods in several epidemiological studies.
Epidemiological data from New Zealand
A study conducted among 2,051 gout patients in New Zealand (Abhishek et al., 2015, subsequently validated by Dalbeth et al.) revealed that 20% of participants identified tomatoes as a trigger for their attacks. Tomatoes thus ranked fourth among self-reported dietary triggers, after seafood, alcohol, and red meat. These results were confirmed by genetic analyses involving more than 16,000 individuals from three distinct cohorts, revealing an association between tomato consumption and genetic markers linked to the renal elimination of uric acid.
"Our findings suggest that tomato is a biologically plausible trigger of gout, and that its effect on uricemia is genetically mediated, independent of its low purine content." — Dalbeth N. et al., BMC Musculoskeletal Disorders, 2015.
Should tomatoes be eliminated from the diet in case of gout?
No, systematically eliminating tomatoes in case of gout is not recommended by medical authorities, unless the patient clearly identifies tomatoes as a personal trigger for their attacks. Gout management is based on an individualized approach, supervised by a physician or rheumatologist.
Tomatoes do in fact offer several nutritional benefits relevant to gout patients:
- They are rich in vitamin C (approximately 14 mg/100 g), an antioxidant associated with a slight reduction in uric acid levels in several studies (Gao et al., 2008, American Journal of Clinical Nutrition).
- They contain lycopene, a carotenoid antioxidant that helps reduce systemic inflammation.
- They are very low in calories (approximately 18 kcal/100 g) and promote hydration, which is beneficial for the renal elimination of uric acid.
- They provide potassium (approximately 237 mg/100 g), a mineral that slightly alkalinizes urine and facilitates urate excretion.
The recommended approach is to keep a food diary to identify correlations between tomato consumption and the occurrence of attacks. To adapt your diet rigorously, consult our guide on what to eat during an acute gout attack.
Which form of tomato carries the highest risk?
Concentrated tomato-based products (tomato paste, purée, industrial sauces) present a potentially higher risk than fresh tomatoes, due to the concentration of their active components. A tablespoon of tomato paste contains the nutritional equivalent of several fresh tomatoes, multiplying exposure to glutamine, glutamic acid, and the fructose naturally present in the fruit.
Ranking of tomato forms by potential risk
- Whole fresh tomato: minimal risk; consume in moderation if sensitivity has been identified.
- Unsalted tomato juice: concentrated glutamic acid content; worth monitoring.
- Lightly cooked homemade tomato sauce: intermediate risk.
- Industrial tomato passata and paste: maximum concentration of active components; highest risk among tomato-based preparations.
- Sun-dried or confit tomatoes: highly concentrated; not recommended in case of confirmed sensitivity to tomatoes.
What other common foods present the same paradox as tomatoes?
Several low-purine foods can nevertheless influence uric acid levels through other mechanisms, particularly via fructose, alcohol, or specific organic acids. Here are the main examples documented in the scientific literature.
- Sweetened fruit juices: fructose (a sugar found in fruits and industrial syrups) directly stimulates hepatic uric acid synthesis, according to a meta-analysis published in 2012 in the British Medical Journal (Choi HK et al.).
- Alcohol, including non-alcoholic beer: ethanol increases lactic acid production, which inhibits renal urate excretion. Our article on gout attack symptoms, causes and treatments examines this point in detail.
- Coffee: conversely, coffee contains chlorogenic acids that appear to reduce uric acid levels. Consult our analysis of whether coffee protects against gout.
- Spinach and asparagus: long suspected, their actual role in triggering attacks is now being called into question by recent studies.
These examples illustrate that the nutritional management of gout cannot be limited to simply counting purines. To learn more about the signs and management of the disease, consult our comprehensive guide on gout attack symptoms, causes and treatments.
Practical recommendations for gout patients
Gout patients can consume fresh tomatoes in reasonable quantities (one to two tomatoes per day, approximately 150 to 200 g) without established risk, unless personal sensitivity has been identified. The recommendations below are based on guidelines from the NHS (National Health Service) and data from PubMed.
- Keep a food diary for 4 to 8 weeks to identify personal trigger foods.
- Prefer fresh tomatoes over paste or industrial sauces enriched with salt.
- Drink at least 2 liters of water per day to promote renal elimination of uric acid.
- Do not eliminate tomatoes without first discussing it with your doctor or dietitian, given their beneficial contributions of vitamin C and lycopene.
- Combine dietary management with urate-lowering drug therapy if this has been prescribed by your general practitioner or rheumatologist.
The CDC (Centers for Disease Control and Prevention) recommends regular monitoring of uric acid levels (every 6 months for patients under treatment) in order to assess the effectiveness of lifestyle and dietary measures. If you have questions about the duration and progression of your disease, our article on gout attack duration with and without treatment will provide useful information.
For patients wishing to understand all the possible complications related to untreated chronic hyperuricemia, we invite you to consult our article on gout complications, risks and prevention.
Frequently Asked Questions
Do tomatoes really increase uric acid?
Tomatoes can increase uric acid in certain genetically predisposed patients, via a mechanism involving glutamine and glutamic acid, independent of their purine content (11 mg/100 g). This sensitivity is not universal: approximately 20% of gout patients identify tomatoes as a trigger for their attacks, according to the study by Dalbeth et al. (2015). An individual assessment, ideally under medical supervision, is necessary before any dietary exclusion.
How many tomatoes can you eat per day when you have gout?
In the absence of identified sensitivity, a consumption of one to two fresh tomatoes per day (approximately 150 to 200 g) is generally considered compatible with gout management. It is recommended to keep a food diary to assess the actual impact on your uric acid levels. If in doubt, a specialist dietitian can help you define your portion sizes.
Is tomato paste more dangerous than fresh tomatoes for gout?
Yes, tomato paste is potentially more problematic than fresh tomatoes because it concentrates amino acids (glutamine, glutamic acid) and natural fructose in a reduced volume. A tablespoon of tomato paste (approximately 18 g) is nutritionally equivalent to several fresh tomatoes. Patients who identify tomatoes as attack triggers should prioritize avoiding concentrated forms.
Can the vitamin C in tomatoes offset their effect on uric acid?
The vitamin C found in tomatoes (approximately 14 mg/100 g) has a slightly uricosuric effect (promoting the elimination of uric acid by the kidneys), documented by a study by Gao et al. published in 2008 in the American Journal of Clinical Nutrition. However, this effect is modest and does not necessarily neutralize the potential impact of glutamine in genetically sensitive patients. Tomatoes should not therefore be considered a therapeutic anti-gout food.
What should I do if I think tomatoes are triggering my gout attacks?
If you suspect a link between tomato consumption and the occurrence of your attacks, record your meals and the appearance of symptoms in a food diary for 6 to 8 weeks. Share these observations with your general practitioner or rheumatologist, who can guide the diagnostic and therapeutic approach. Eliminating a food should not be done without medical advice, in order to avoid unnecessary nutritional deficiencies.