A 2019 Taiwanese study 1 recently reported on the results of two large-scale cohort studies which were analysed in order to establish whether following a vegetarian diet reduces the risk of developing gout, when compared with following a non-vegetarian diet.
What is gout?
This subject has been covered extensively in a previous blog 2 so, in brief terms: gout is the most common inflammatory joint disease and is an important risk factor for hypertension, diabetes, kidney diseases, cardiovascular diseases, and all-cause and cardiovascular mortality 3 4 5 6 gout pathogenesis begins with excess serum urate that forms monosodium urate crystals – a salt or ester of uric acid – in the joints, triggering gouty inflammation and resulting in excruciating pain 7 8 cases of gout have doubled or tripled in many countries in the past decades 9 10 making it a serious public health threat which desperately requires preventive strategies Taiwan is particularly affected, with one of the highest incidences and prevalences of gout in the world 11
Two cohort groups, representing almost 14,000 Taiwanese, were followed for between 7 and 9 years. They were divided into vegetarians (n=4684) and non-vegetarians (n=9251), and appropriate tests were undertaken to establish gout occurrence.
Study assumptions the standard therapeutic diet aimed at preventing/managing gout restricts purine intake which is metabolised into urate and contributes to one-third of the body’s total urate pool 12 however, purine exclusion diets have only moderate urate-lowering effects and are generally regarded as an insufficient remedy 13 the researchers considered that the ideal diet for gout prevention/management should be able to simultaneously reduce uric acid and inflammation, while preventing gout-associated comorbidities they conjectured that a vegetarian diet may be a promising dietary pattern to target multiple pathways in the gout pathogenesis, since: vegetarians avoid purine-rich meat/seafood, while consuming increased amounts of vegetables, whole grains, seeds and nuts 14 15 plant foods contain polyphenols which potentially reduce uric acid via both an inhibition of xanthine oxidase 16 activities and the enhancement of uric acid excretion 17 plant foods contain phytochemicals which potentially attenuate the NLRP3 18 inflammatory pathway 19 20 vegetarian diets have already been shown to reduce gout associated comorbidities, such as cardiovascular diseases 21 , diabetes 22 23 , and hypertension 24 25
“ In these two prospective cohort studies, a Taiwanese vegetarian diet is associated with lower risk of gout. This association persists after controlling for demographic, lifestyle, cardiometabolic risk factors, and baseline hyperuricemia. This finding does not differ across subgroups of sex, lifestyle factors, or comorbidities. ” it’s most likely that vegetarians experienced a lower risk of gout simply because they had lower uric acid levels since their diets avoid purine-rich meat and seafood – a diet which in prospective studies has been shown to increase gout incidence and recurrence 26 27 28 29 the results appear to go beyond the single effects of uric acid levels, since they were not consistently wide apart between all vegetarians and all non-vegetarians. The other potential factors influencing the reduction of gout in vegetarians may also be accounted for by the following: vegetarian diets have higher alkalinity which has been shown to facilitate more effective uric acid excretion than an acidic diet – i.e. one that is fish/meat-based 30 vegetarian diets usually contain lower saturated fat, higher unsaturated fat and phytochemical-rich plant foods 14 15 31 the latter may prevent inflammatory responses which trigger gout attacks by dampening the inflammatory activation of NLRP3 inflammasome 32 fibre (high in plant-based diets) on its own, and when metabolised into short chain fatty acids by gut microbiota, has been shown to resolve inflammatory responses involved in gout attacks in mice 33 and in humans 34
We saw in the previous gout blog 2 that there’s plenty of strong evidence to suggest that the best possible dietary option for gout-avoidance is a WFPB diet (with zero alcohol!). Of course, any diet which favours plant over animal foods will be of some benefit, and the more the latter is replaced with the former, the better in terms of gout-avoidance.
One interesting finding from this Taiwanese study relates to soy. Taiwanese vegetarian diets replace meat and seafood with soy products. But there appears to be a paradox here. Soy has a high purine content and has attracted an infamous reputation – even amongst health professionals – for causing gout 35 . However, contrary to this widely-held belief, the vegetarian diets with high soy content covered in this present Taiwanese study appear to lower gout risk.
And this is not the only study to show this. The researchers’ findings are consistent with the “Singapore Chinese Health Study” which found that soy was protective toward gout 27 .
A potential explanation for this rests in the fact that the potential of soy purines – mainly adenosine 36 and guanine 37 – to raise uric acid levels is considerably lower than those in meat and fish, which have a higher proportion of their purines in the form of hypoxanthine 38 39 40
A 2012 prospective study 41 of gout patients found that the impact of plant purine on gout attacks was significantly less than the purine from animal sources.
Finally, research suggests 42 that soy may have the ability to prevent gout through the inhibition of both the above-mentioned NLRP3 inflammatory pathway and the activity of the caspase-1 enzyme. The latter is an essential effector of inflammation, pyroptosis 43 , and septic shock 44 .
So, hurrah for the plants, boo hiss for meat and seafood, and don’t be shy about eating soy…
This content was originally published here.