No effect of increased water intake on blood viscosity and cardiovascular risk factors

Abstract

Observational data have suggested that increased water intake decreases the risk of CHD. A postulated mechanism is that increased water ingestion reduces blood viscosity. The aim of the present study was to assess the effect of increased fluid intake on blood viscosity. Men (n 67) and postmenopausal women (n 27) with one or more risk factors for CVD who reported intake of #0·5 litres water daily were randomised to a control group (n 31), an intervention group (n 32) that increased their daily water intake by 1 litre/d and an intervention group (n 31) that ingested 1 litre blueberry juice/d. All were encouraged to continue their usual diet and lifestyle. Whole-blood viscosity and blood and urine chemistries were measured by standard techniques after 2 and 4 weeks. Urine volume increased (by a median of 872 and 725 ml in the water and blueberry juice groups, respectively, v. 10 ml in the control group; P# 0·002), confirming the subjects' adherence to the protocol. Urine osmolality and urinary levels of Na, K and creatinine decreased in the water and blueberry juice groups v. the controls (P, 0·05). No change was seen in whole-blood viscosity or in levels of fibrinogen, total protein, lipids, glucose, insulin, C-peptide or other chemistry and haematology variables. In conclusion, a postulated protective effect of increased water or fluid intake is not explained by a change in blood viscosity and increased fluid intake does not influence CVD risk factors in the short term.Blood viscosity: Water: Fluids: Coronary heart disease risk factors Few studies have investigated the effect of water intake on the incidence of CVD. In the Adventist Health Study there was a dose-relationship between water intake and protection against fatal CHD (Chan et al. 2002). One of the suggested mechanisms of this effect is that water ingestion may reduce blood viscosity; however, a recent systematic review found no direct evidence that a decrease in viscosity due to high fluid intake can prevent CVD (Okamura et al. 2005).The primary determinants of whole-blood viscosity are plasma viscosity, packed cell volume and macromolecules, including fibrinogen. Initial reports indicated that plasma viscosity (Yarnell et al. 1991) and packed cell volume (Gagnon et al. 1994) were independent predictors of CVD. Subsequently, whole-blood viscosity and packed cell volume were shown to be independent predictors of coronary events (Danesh et al. 2000). The major CVD risk factors are independently associated with whole-blood or plasma viscosity (Bonithon-Kopp et al. 1993;Fossum et al. 1997). Thus, increased viscosity may be one mechanism by which cardiovascular risk factors promote atherosclerosis and plaque formation (Lee et al. 1998). Whole-blood or plasma viscosity is inversely related to insulin sensitivity (Høieggen et al. 1998) and strongly related to metabolic risk factors (Fossum et al. 1997).Given this background, the question of whether increased water intake reduces blood viscosity is of interest, but only limited data exist. We examined the effe...

Association between Water Intake, Chronic Kidney Disease, and Cardiovascular Disease: A Cross-Sectional Analysis of NHANES Data

“…There is some evidence that dehydration might contribute to increased blood viscosity [60,61], a known risk factor for ischemic heart disease and stroke [62,63]. However, several interventions have failed to reduce blood viscosity with greater fluid intake [60,61,64,65] — possibly because a benefit of greater water intake may not be realized in patients who are adequately hydrated, as appeared to be the case in one trial, where the baseline urine volume of patients was ∼1.6 l/day [65]. Few studies have evaluated the direct effect of water intake on cardiovascular outcomes, and these have produced equivocal results.…”

Total fluid and specific beverage intake and mortality due to IHD and stroke in the Netherlands Cohort Study

“…Furthermore, it has been suggested that water consumption at night can attenuate nocturnal increase in blood viscosity, and therefore, can prevent morning occurrence of cerebral infarction (9) . Some investigators reported a decrease in blood viscosity with increased water intake (9,13,14) , while others reported no changes in blood haemorheology and chemistry with increased water intake (15) . Only one cohort study analysed the effect of water intake and other fluid intake on fatal CHD (1) .…”

Prevention and Therapy of Type 2 Diabetes—What Is the Potential of Daily Water Intake and Its Mineral Nutrients?

“…Table 3 : RCTs comparing water with other drinks or no drink (eight studies); [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ].…”

“…Regarding the study populations investigated, we included four studies with type 2 diabetes [ 19 , 22 , 23 , 24 ], three with overweight or obese [ 17 , 18 , 21 ], three with moderately elevated cholesterol [ 26 , 27 , 29 ], one with at least one CVRF [ 20 ] and four with healthy participants [ 16 , 25 , 28 , 30 ].…”