Abstract
A long-standing body of clinical observations associates low 24-h total water intake (TWI = water + beverages + food moisture) with acute renal disorders such as kidney stones and urinary tract infections. These findings prompted observational studies and experimental interventions comparing habitual low volume (LOW) and high volume (HIGH) drinkers. Investigators have learned that the TWI of LOW and HIGH differ by 1–2 L·d−1, their hematological values (e.g., plasma osmolality, plasma sodium) are similar and lie within the laboratory reference ranges of healthy adults and both groups appear to successfully maintain water-electrolyte homeostasis. However, LOW differs from HIGH in urinary biomarkers (e.g., reduced urine volume and increased osmolality or specific gravity), as well as higher plasma concentrations of arginine vasopressin (AVP) and cortisol. Further, evidence suggests that both a low daily TWI and/or elevated plasma AVP influence the development and progression of metabolic syndrome, diabetes, obesity, chronic kidney disease, hypertension and cardiovascular disease. Based on these studies, we propose a theory of increased disease risk in LOW that involves chronic release of fluid-electrolyte (i.e., AVP) and stress (i.e., cortisol) hormones. This narrative review describes small but important differences between LOW and HIGH, advises future investigations and provides practical dietary recommendations for LOW that are intended to decrease their risk of chronic diseases.
Highlights
Water is essential for digestion, circulation of nutrients, movement of substances across cell membranes, metabolism and regulation of intracellular-extracellular concentration
Nutrients 2020, 12, 858 and pressure; renal sodium retention as part of the renin-angiotensin-aldosterone system (RAAS); stimulates thirst and arginine vasopressin (AVP) release); oropharyngeal afferent signals that modulates thirst, drinking, plasma AVP and plasma angiotensin II (ANG II) [1,4] and release of atrial natriuretic peptide (ANP; a hormone released in response to atrial stretch receptors) and apelin to remediate plasma volume expansion and dilution
When physiologists discovered that both low volume (LOW) and high volume (HIGH) exhibited a normal plasma osmolality (POSM) and body weight but that LOW had higher plasma AVP compared to HIGH, they began to ask, “What are the possible mechanisms of long-term negative health effects that result from habitually consuming a small volume of water?”
Summary
Water is essential for digestion, circulation of nutrients, movement of substances across cell membranes, metabolism and regulation of intracellular-extracellular concentration. When physiologists discovered that both LOW and HIGH exhibited a normal POSM and body weight (i.e., suggesting euhydration) but that LOW had higher plasma AVP compared to HIGH, they began to ask, “What are the possible mechanisms of long-term negative health effects that result from habitually consuming a small volume of water?” This prompted human epidemiological studies which eventually revealed statistically significant links between elevation of plasma AVP or copeptin (i.e., released in equimolar quantities with AVP) and increased risk of developing diabetes [29,30,31], hyperglycemia [32], insulin resistance, metabolic syndrome [33,34], abdominal obesity [35], stroke, cardiovascular disease, cardiovascular events, cardiovascular death [7,36,37,38], hypertension [34] and kidney disease [38,39,40]. To propose dietary and hydration recommendations for LOW that encourage increased daily TWI and decrease plasma AVP concentration
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