Plain-water intake and risk of type 2 diabetes in young and middle-aged women.

BACKGROUND: The replacement of caloric beverages such as sugar-sweetened beverages (SSBs) and fruit juices with noncaloric beverages such as plain water has been recommended for diabetes prevention.

OBJECTIVE: We evaluated the relation of plain-water intake and the substitution of plain water for SSBs and fruit juices with incident type 2 diabetes (T2D) in US women.

DESIGN: We prospectively followed 82,902 women in the Nurses' Health Study II who were free of diabetes, cardiovascular disease, or cancer at baseline. Diet, including various beverages, was assessed by using validated food-frequency questionnaires and updated every 4 y. Incident T2D was confirmed by using a validated supplementary questionnaire. We used a 4-y lagged analysis to minimize reverse causation (ie, increased water consumption that was due to early stage of diabetes).

RESULTS: During 1,115,427 person-years of follow-up, we documented 2718 incident T2D cases. Plain-water intake was not associated with T2D risk in the multivariable-adjusted model that included age, BMI, diet, and lifestyle factors; RRs (95% CIs) across categories (<1, 1, 2-3, 4-5, and ≥6 cups/d) were 1.00, 0.93 (0.82, 1.05), 0.93 (0.83, 1.05), 1.09 (0.96, 1.24), and 1.06 (0.91, 1.23), respectively (P-trend = 0.15). We estimated that the replacement of 1 serving SSBs and fruit juices/d by 1 cup plain water/d was associated with 7% (3%, 11%) and 8% (2%, 13%) lower risk of T2D, respectively.

CONCLUSIONS: Plain-water intake, per se, was not significantly associated with risk of T2D. However, substitution of plain water for SSBs or fruit juices was estimated to be associated with modestly lower risk of T2D.