What was once called the “disease of kings” could now just as well be called the “disease of commoners.” Gout is now the most common form of inflammatory arthritis worldwide, with its prevalence rising in many countries.1 Based on data from the National Health and Nutrition Examination Survey 2015-2016, an estimated 9.2 million Americans have gout and the total number of Americans with hyperuricemia is 32.5 million.2 Gout is often associated with other metabolic disorders (metabolic syndrome, diabetes mellitus, dyslipidemia, stroke, and cardiovascular diseases).3
Concerns have been expressed that gouty patients should avoid soyfoods as should individuals at risk of developing grout.4 To this point, a survey of 227 physicians and dietitians from Singapore, Indonesia and Thailand found that on average 48% indicated that gout is one of the undesirable effects of soyfood consumption.4 That figure was 3 times higher than the percentage of respondents expressing concern about soy and breast cancer. However, substantial clinical and epidemiologic evidence shows these concerns to be without scientific foundation.4
Identification of monosodium urate crystals in joints and in tophi is considered the gold standard for the diagnosis of gout.5 Uric acid is the final enzymatic product in the degradation of purine nucleosides and free bases in humans. Although data are not totally consistent, epidemiological surveys have found an association between the intake of purine-rich foods and serum uric acid concentrations6,7 and gout.8,9 Further, acute purine intake increases the risk of recurrent gout attacks by almost fivefold.10
Of the total amount of urate in the body, about two-thirds is produced endogenously and about one-third comes from dietary purines.11 Experts often recommend reducing the consumption of purine-rich animal protein to reduce risk of recurrent gout attacks.10,12 Lists of foods grouped according to their purine content are commonly used as a basis for devising low-purine diets for gout patients. However, such lists do not account for findings showing that purine bases and metabolites involved in the endogenous synthesis of purines affect serum uric acid levels differently.13 Therefore, dietary recommendations should not be based solely on the average purine content of a food, but also on how that food affects plasma urate.7
Lists of the purine content of foods generally list soyfoods as having a moderate amount of purines, ranging from 50 to 100 mg/100 g. However, until recently, relatively little peer-reviewed data were available. In 2014, this void was filled by Kaneko et al,14 who provided data on the purine content of 270 foods (mg/100 g). Foods were classified from 1 to 5 according to their purine content with 1 representing foods very low in purines and 5 those foods very high in purines. As can be seen from the table, most soyfoods have a low rating.
|Bean curd lees (Okara)||1|
|Green soybean (edamame)||1|
|Tofu (Momen, chilled)||1|
|Tofu (Momen, 3 min boiled)||1|
|Fermented soybean (Natto)||3|
|Freeze dried tofu||4|
However, as noted previously, one has to consider the impact on serum urate levels, not just the amount of purines in a food. After extensively reviewing the human data, my colleagues and I concluded4 that “none of the six epidemiologic studies identified provided any evidence that soy intake was associated with circulating uric acid levels, hyperuricemia or gout.” These authors also noted that “data from the five human intervention studies evaluated indicate soy protein does elevate serum uric levels, but in response to amounts comparable to Asian intake, the expected rise would almost certainly be clinically irrelevant.”4
Finally, very recently Zhang et al.15 examined the effect of soyfood intake on serum uric acid levels in 50 healthy Chinese adult men. Serum acid levels did not increase in response to tofu consumption, whereas they did in response to the ingestion of whole soybeans, soy powder, and soymilk. However, urate levels increased by less than 10%. Furthermore, each of the soyfoods provided more soy protein (40 g) at a single meal than is typically recommended for consumption for an entire day. Also, and very importantly, the comparator (control) wasn’t a non-soyfood, but water. Therefore, overall, the results are consistent with the conclusion we reached in 2011, 4 that soyfoods do not increase risk of developing gout.
- Kuo CF, Grainge MJ, Zhang W, et al. Global epidemiology of gout: prevalence, incidence and risk factors. Nat Rev Rheumatol. 2015;11(11):649-62.
- Singh G, Lingala B, Mithal A. Gout and hyperuricaemia in the USA: prevalence and trends. Rheumatology (Oxford). 2019.
- Choi HK, McCormick N, Lu N, et al. Population impact attributable to modifiable risk factors for hyperuricemia. Arthritis Rheumatol. 2019.
- Messina M, Messina VL, Chan P. Soyfoods, hyperuricemia and gout: A review of the epidemiologic and clinical data. Asia Pacific journal of clinical nutrition. 2011;20(3):347-58.
- Pascual E, Batlle-Gualda E, Martinez A, et al. Synovial fluid analysis for diagnosis of intercritical gout. Ann Intern Med. 1999;131(10):756-9.
- 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;52(1):283-9.
- Zgaga L, Theodoratou E, Kyle J, et al. The association of dietary intake of purine-rich vegetables, sugar-sweetened beverages and dairy with plasma urate, in a cross-sectional study. PloS one. 2012;7(6):e38123.
- Choi HK, Atkinson K, Karlson EW, et al. Purine-rich foods, dairy and protein intake, and the risk of gout in men. N Engl J Med. 2004;350(11):1093-103.
- Villegas R, Xiang YB, Elasy T, et al. Purine-rich foods, protein intake, and the prevalence of hyperuricemia: the Shanghai Men’s Health Study. Nutrition, metabolism, and cardiovascular diseases : NMCD. 2012;22(5):409-16.
- Zhang Y, Chen C, Choi H, et al. Purine-rich foods intake and recurrent gout attacks. Ann Rheum Dis. 2012;71(9):1448-53.
- Schlesinger N. Dietary factors and hyperuricaemia. Curr Pharm Des. 2005;11(32):4133-8.
- Hainer L, Matheson E, Wilkes Travis R. Diagnosis, treatment and prevention of gout. Am Fam Physician. 2014;90831-6.
- Clifford AJ, Riumallo JA, Young VR, et al. Effect of oral purines on serum and urinary uric acid of normal, hyperuricemic and gouty humans. J Nutr. 1976;106428-34.
- Kaneko K, Aoyagi Y, Fukuuchi T, et al. Total purine and purine base content of common foodstuffs for facilitating nutritional therapy for gout and hyperuricemia. Biol Pharm Bull. 2014;37(5):709-21.
- Zhang M, Lin L, Liu H. Acute effect of soy and soy products on serum uric acid concentration among healthy Chinese men. Asia Pacific journal of clinical nutrition. 2018;27(6):1239-42.