Relationship between soy milk intake and radiographic knee joint space narrowing and osteophytes

The purpose of this study was to examine the cross-sectional association between dietary soy milk intake and the prevalence of radiographic knee joint space narrowing (JSN) and osteophytes (OST). Soy milk intake was assessed using a validated semiquantitative food frequency questionnaire and classified into three categories: never, <once a day, and ≥once a day. JSN and OST were assessed individually based on the Osteoarthritis Research Society International atlas. Multivariable logistic models were used after adjusting for potentially confounding factors. A total of 5764 subjects were included. Both the models suggested a significant inverse association between soy milk intake and OST. In model 1 (adjusted for age, body mass index, and sex), the prevalence of OST decreased in “≥once a day” category (OR 0.52, 95 % CI 0.28–0.98, P = 0.042) and “<once a day” category (OR 0.78, 95 % CI 0.66–0.93, P = 0.005) comparing to “never” category of soy milk intake, and the P for trend was 0.001. The outcomes were similar in model 2 (adjusted based on model 1, with additional factors of total energy intake, activity level, smoking status, alcohol-drinking status, educational background, diabetes, hypertension, and other dairy product intake) (“≥once a day” category: OR 0.49, 95 % CI 0.26–0.92, P = 0.026; “<once a day” category: OR 0.79, 95 % CI 0.67–0.94, P = 0.009), and the P for trend was 0.001. However, the significant associations between soy milk intake and JSN in both the models were not observed. Dietary soy milk intake was found to be negatively associated with OST, but not JSN, independent of some major confounding factors.