A systematic review of 18 randomized clinical trials found that increasing daily water intake was associated with several health benefits, according to findings published in JAMA Network Open. The review analyzed studies with intervention durations ranging from 4 days to 5 years.

Three randomized clinical trials (RCTs) demonstrated that adults with overweight or obesity who consumed approximately 500 mL of water before meals achieved 44% to 100% greater weight loss compared with control groups over periods of 12 weeks to 12 months. A fourth RCT involving adolescents showed no significant effect on weight (effect size, -0.0 [95% CI, -0.1 to 0.1]; P = .88).

For kidney stone prevention, one 5-year trial found that increasing water intake to achieve 2000 mL daily urine volume resulted in significantly lower stone recurrence rates in the intervention group (12 of 99 participants) compared with the control group (27 of 100 participants) (P = .008).

In patients with recurrent headaches, increased water intake of 1500 mL daily was associated with improved quality of life scores (4.5 [95% CI, 1.3 to 7.8] points; P = .007), though the reduction in headache days was not statistically significant. For premenopausal women with recurrent urinary tract infections who drank less than 1500 mL fluid daily, increasing water intake by 1500 mL was associated with fewer infection episodes (1.5 [95% CI, 1.2-1.8]; P < .001). In patients with type 2 diabetes, a premeal water intervention totaling 1000 mL daily led to decreased fasting blood glucose (-32.6 mg/dL vs +5.3 mg/dL in control; P = .003).

Of the included trials, 10 (55%) reported at least one positive result, while 8 (44%) reported negative results. The authors noted that while the quantity and quality of evidence was limited, the findings suggest potential benefits in specific conditions.

This article has been edited for brevity. Full methods, results, and disclosures are available in the published review.