INTRODUCTION
Several modifiable risk factors such as tobacco use, unhealthy diet, and excessive alcohol intake are linked to the greater risk of non-communicable diseases, some evidence suggests that adequate water intake may improve health outcomes[1]. Adequate hydration and water intake are necessary for critical physiological and metabolic processes[2]. Using this framework dietary guidelines recommended consumption of 2 and 2.5 L per day from water for females and males respectively[3]. Low fluid consumption and inadequate water intake may provoke dehydration. This condition can lead to low-grade inflammation in the human body. It should be noted that the low-grade inflammation in long-term was associated with inanition and progression of some chronic diseases[4], CVD[5], and mortality[6]. Previous meta-analysis on the association of specific beverages, such as tea[7, 8], coffee[9, 10], and alcohol[11-13] with mortality reported inverse, positive or null associations. Findings on the link between water intake and longevity remain an unresolved question. While total water intake from foods and beverages was associated with a lower risk of mortality in some investigations[14] others failed to find such evidence[15, 16]. No information is available about the strength and shape of dose-response relation between water intake and risk of mortality. On the other hand, understanding the association between water consumption and mortality is important for guiding consumers and prioritizing dietary guidelines to reduce the risk. Therefore, in the current study, we conducted a systematic review and dose-response meta-analysis of prospective cohort studies to summarize the association between total water intake from foods and beverages and drinking intake and risk of mortality from all causes and CVD.