by Taylor Wolfram, MS, RDN, LDN • Last updated: September 2019
- Uric Acid Levels and Rates of Gout among Vegetarians and Vegans
- Soy Intake and Uric Acid Levels
Gout is a form of arthritis that is characterized by flare-ups of inflamed, painful joints. It’s caused by a buildup of uric acid in the body. Uric acid (UA) is a product of the body metabolizing purines. Uric acid can build up because someone’s body produces too much of it, the kidneys aren’t getting rid of it correctly, or because they’re consuming too much purine-rich food (1).
Purine-rich foods include meat, seafood, and alcohol and standard gout management includes limiting these foods, especially during flare-ups. Some plant-based foods contain smaller amounts of purines, such as legumes, whole grains, asparagus, cauliflower, spinach, mushrooms, and green peas (2). It’s impossible to eat a completely purine-free diet.
The extent to which diet impacts risk for gout has been debated in the medical community. In addition to animal proteins and alcohol, sugar-sweetened beverages have been suspected as playing a role in the development of gout. Many people who experience gout also have another chronic condition, such as type 2 diabetes, kidney disease, or hypertension (3). Medication is a standard treatment for gout, and dietary modification may improve symptoms.
Diet is not the only risk factor for developing gout. Family history, lead exposure, and certain medications also can increase the risk of developing gout. Men, older adults, and inactive people are more likely to develop gout than women, younger individuals, and those who are active (1).
Uric Acid Levels and Rates of Gout among Vegetarians and Vegans
Data from the EPIC-Oxford cohort showed that vegans had higher levels of serum uric acid compared to meat-eaters, fish eaters, and vegetarians (5). Researchers hypothesized this was due to vegans’ lower intake of calcium and avoidance of dairy. In this study, there was an inverse relationship with uric acid and intakes of dairy and calcium. Previous studies have found that higher dairy intake was associated with lower uric acid (6).
A 2018 review of two prospective cohort studies of Taiwanese participants found that plant-based diets were associated with a lower risk of gout after controlling for demographic, lifestyle, and cardiometabolic risk factors (4). In one cohort, lacto-ovo vegetarians had the lowest levels of uric acid, followed by vegans and nonvegetarians. In this cohort, vegetarians had lower intakes of meat, fish, dairy, eggs, coffee, tea, and sugar-sweetened beverages compared with nonvegetarians.
A 2019 review on uric acid and plant-based nutrition concluded, “studies that compared UA serum concentrations in vegetarians and nonvegetarians have consistently shown a lower mean UA serum concentration in vegetarians (16).”
Soy Intake and Uric Acid Levels
A small 2010 randomized controlled trial including 16 healthy males found that consuming soy milk led to a 10% increase in serum uric acid while consuming skim milk resulted in a 10% decrease in serum uric acid (11). Servings contained 80 grams of protein, which is much more than is typically eaten in one sitting, so the relevance of these findings for most people is questionable. For reference, this is about 11.5 cups, or 2.7 liters, of soy milk.
A 2011 cross-sectional study of 3,978 Chinese men found an inverse association between plant protein intake and uric acid levels (12). Intake of soy foods, including tofu and soy milk, was associated with lower uric acid levels.
A 2011 review of epidemiologic and clinical data concluded that there’s no reason for those with gout or at risk of developing gout to avoid soy foods (10). Researchers emphasized the need for long-term studies to help clarify any associations between soy intake and uric acid levels.
A 2015 pooled analysis of two randomized controlled trials including postmenopausal Chinese women with prediabetes or hypertension found the intake of soy foods was not associated with increased uric acid levels (9). Furthermore, data from the Singapore Chinese Health Study of 63,257 Chinese adults, also published in 2015, demonstrated that the consumption of soy and non-soy legumes was associated with decreased risk of gout (13).
A 2018 randomized controlled trial investigating the impact of soy consumption on uric acid concentrations included 60 healthy Chinese men. Researchers found that consuming different types of soy-based foods had varying effects on uric acid levels (8). Consuming whole soybeans, soy powder, and soy milk caused a significant increase in uric acid within one to two hours after consuming the foods. Bean curd cake (this is not tofu) and dried bean curd stick did not cause significant changes in uric acid levels. Servings of these foods had 40 grams of protein, which is larger than amounts of soy protein typically eaten in one sitting.
Based on this evidence we can draw two potential conclusions:
- Any rise in uric acid levels after eating soy foods is due to large amounts not customarily eaten and we cannot assume that clinically meaningful rises in uric acid would occur after eating a typical amount of soy foods.
- Men may have more sensitive uric acid responses to soy intake than women.
At this point in time, we cannot recommend that people avoid soy to reduce the risk of developing gout. If you have gout and find that flare-ups tend to occur after eating soy, you may consider experimenting with different types or amounts of soy foods.
In 2017, the British Society for Rheumatology released their Guideline for the Management of Gout, in which they encourage the consumption of soy and other plant proteins (14). And in a 2019 article by the American College of Rheumatology, they state, “[n]ew research has found purines in vegetables appear to be safe (15).”
A 2019 review concludes, “there are no data from long-term cross-sectional or interventional studies that would show that high-purine plant-based foods represent a clinically meaningful increased risk for hyperuricemia or gout development (16).”
5. Schmidt JA, Crowe FL, Appleby PN, Key TJ, Travis RC. Serum uric acid concentrations in meat eaters, fish eaters, vegetarians and vegans: a cross-sectional analysis in the EPIC-Oxford cohort. PLoS One. 2013;8(2):e56339.
6. Choi HK, Liu S, Curhan G. Intake of purine-rich foods, protein, and dairy products and relationship to serum levels of uric acid: the Third National Health and Nutrition Examination Survey. Arthritis Rheum. 2005 Jan;52(1):283-9.
7. Becerra-Tomás N, Mena-Sánchez G, Díaz-López A, et al. Cross-sectional association between non-soy legume consumption, serum uric acid and hyperuricemia: the PREDIMED-Plus study. Eur J Nutr. 2019 Aug 5.
9. Liu ZM, Ho CS, Chen YM, Woo J. Can soy intake affect serum uric acid level? Pooled analysis from two 6-month randomized controlled trials among Chinese postmenopausal women with prediabetes or prehypertension. Eur J Nutr. 2015 Feb;54(1):51-8.
12. R. Villegas, Y.-B. Xiangb, T. Elasy, et al. Purine-rich foods, protein intake, and the prevalence of hyperuricemia: The Shanghai Men’s Health Study. Nutr Metab Cardiovasc Dis. 2012 May; 22(5): 409–416.