Tomatoes being a possible cause of gout is probably one of the most divisive topics when it comes to gout and what you should or shouldn’t.
Tomatoes are very low in purines, are 90% water and contain a number of compounds which are beneficial to a eating a healthy diet.
On the surface they appear to be the perfect food.
Interestingly though, according to a study conducted by the University of Otago in which 2,051 New Zealanders of Maori, Pacific Island and European ancestry were asked to list their most common gout triggers, tomatoes were the fourth most common dietary gout trigger behind seafood, alcohol and red meat.
Of this group, Maori and Pacific Islanders were more likely to report tomatoes as a gout trigger than European Caucasian (this was independent of indicators of severity, including number of acute attacks per year).
Tomato has also previously been reported as a food avoided by Australian gout patients, with the authors of that study noting that the current evidence does not support this avoidance.
Low in Purines but High in Glutamine
Although tomatoes are low in purines, there is some thought that the high levels of glutamine in tomatoes may stimulate the synthesis or urate by acting as a nitrogen donor in the purine synthesis pathway.
Glutamine is an amino acid often found in foods with a high purine content.
European individuals from the Atherosclerosis Risk In Communities (ARIC; n = 7517) Study, Cardiovascular Health Study (CHS; n = 2151) and Framingham Heart Study (FHS; n = 3052) were used to test, in multivariate-adjusted analyses, for association between serum urate and tomato intake.
The University of Otago study provided evidence that tomato consumption is positively associated with serum urate in European Caucasians which suggests that the avoidance by gout patients is not a baseless practice.
It is useful to compare the increase in serum urate attributed to a one serve per week increase in tomato consumption (0.7 μmolL) with other recognised gout attack trigger foods that also increase serum urate (men and women combined).
Alcohol increased serum urate by 2.3 μmolL per serving per week in the United States third National Health and Nutrition Examination Survey (NHANES).
In the ARIC (Atherosclerosis Risk In Communities) sample set sugar-sweetened drinks increased urate 0.4 μmolL per serve per week.
In the third NHANES sample set total meat and seafood increased urate 0.5 μmolL and 2.4 μmolL per extra serve per week, respectively.
Thus – according to this study – tomatoes alter serum urate levels to an extent comparable to other established dietary risk factors for gout.
So, should you avoid tomatoes?
According to this study, the positive association between tomato consumption and serum urate levels supports the hypothesis that the self-reporting of tomatoes as a dietary trigger by people with gout has a biological basis.
Further research into the relationship between gout (and onset of gout attacks) and tomatoes needs to be conducted, to further investigate this relationship, potentially with a case-crossover study design, as previously used to demonstrate a purine-rich diet and alcohol as triggers of acute gout attacks.
Analysis of any effect on urinary uric acid excretion and glutamate metabolism is also required to identify the mechanisms behind this association.
The research on tomatoes and gout is still reasonably thin. While there is a positive association between tomatoes and their impact on raising uric acid levels, it’s not understood exactly why this is the case due to tomatoes not fitting the typical description of a risky gout-inducing food.
I’m also of the belief that different foods affects each person differently due to genetics, age, gender, ethnicity, weight and what makes up the rest of their diet. Tomatoes in one persons diet may pose no risk, but when paired with someone else’s diet may see some negative interplay with another food type which causes increase urate levels.
My advice is if you suffer from gout regularly or are currently in the middle of a gout attack, limit portions of tomatoes in your diet to 1-2 per week.
Eliminating tomatoes completely for a significant period of time (at least 3 months) would be a useful experiment if you think tomatoes are a gout trigger. Slowly re-introde tomatoes after this exclusion period and closely monitor for the common signs of an oncoming gout attack.
Of course, you should avoid tomatoes where extra sugar has been added, for example tomato sauce and BBQ sauce.
Also consider what you’re eating tomato with, for example is the tomato in a salad or is it in a burger accompanied by other potential gout triggers like beef?