Sodium status is associated with type 2 diabetes mellitus: a systematic review and meta-analysis of observational studies.

The relationship between sodium intake and the risk of developing type 2 diabetes mellitus (T2DM) is inconsistent. We, therefore, aimed to summarize the current evidence by conducting a systematic review and meta-analysis of observational studies. We retrieved studies which compared any marker of sodium status between individuals with T2DM and those without diabetes published in any language by searching online databases from inception up to June 2019. Summary effects were derived using random-effects model. A total of 44 studies with 503,830 participants from 25 countries were included in this study. Sodium status was significantly different between individuals with and without T2DM (Hedges’ g = 0.21; 95% CI 0.02, 0.40; P = 0.029). Individuals with T2DM had higher sodium intake compared to non-diabetic controls (WMD = 621.79 mg/day; 95% CI 321.53, 922.06; P < 0.001) and 24-h urinary excretion was associated with likelihood of developing T2DM (OR = 1.27, 95% CI 1.15, 1.41; P < 0.001). Furthermore, salivary, hair, and platelet sodium were higher in patients with T2DM compared to controls (P < 0.05). The findings of the current meta-analysis suggest that sodium levels are higher in patients with T2DM compared to non-diabetic controls; however, given that these studies are observational, it is not possible to infer causality.