PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 16028570

Human water needs.

Michael N Sawka·Samuel N Cheuvront·Robert Carter
View original source ↗Export metadata ↓

Abstract

Healthy humans regulate daily water balance remarkably well across their lifespan despite changes in biological development and exposure to stressors on hydration status. Acute or chronic body water deficits result when intakes are reduced or losses increase, but day-to-day hydration is generally well maintained so long as food and fluid are readily available. Total water intake includes drinking water, water in beverages, and water in food. Daily water needs determined from fluid balance, water turnover, or consumption studies provide similar values for a given set of conditions. A daily water intake of 3.7 L for adult men and 2.7 L for adult women meets the needs of the vast majority of persons. However, strenuous physical exercise and heat stress can greatly increase daily water needs, and the individual variability between athletes can be substantial.

Explore related subjects

Body WaterDehydrationExerciseHumansNutritional RequirementsWaterJournal ArticleReview

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Michael N Sawka, Samuel N Cheuvront, Robert Carter. 2005. Human water needs.. https://doi.org/10.1111/j.1753-4887.2005.tb00152.x

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Decrease in extracellular collagen crosslinking after NMR magnetic field application in skin fibroblasts.

Although biological effects of electromagnetic fields were investigated intensively, there is still no agreement on the significance of their effects. The underlying mechanisms and therapeutic importance are still mostly unknown too. In this study, primary cultures of human dermal fibroblasts were exposed to magnetic field at nuclear magnetic resonance (NMR) conditions for in total 5 days and 4 h/day. Among the investigated parameters were: cell proliferation rate, cell morphology, total protein concentration as well as content of skin-specific collagen types I, III, IV. NMR exposure induced distinct changes both in cellular and extracellular components. The extracellular matrix (ECM) of NMR-exposed cells had less cross-linked collagen. In particular, the increase of collagen of the soluble fraction was at 17.2 +/- 2.9% for type I, 27.0 +/- 1.86% for type III, 17.3 +/- 1.46% for type IV (N = 6). In the absence of resonance frequency, the effects of magnetic field on ECM were less profound.

Body Water↗
PubMed2007

Correlation between net water flux and absorptive clearance determined from in situ intestinal perfusion studies does not necessarily indicate a solvent drag effect.

Estimation of absorptive clearance (PeA) of drugs from in situ perfusion studies, based on the disappearance of drugs from the intestinal lumen, involves correcting outflow perfusate drug concentration with net water flux (Jw). However, as demonstrated through both theoretical derivations and simulations, the PeA estimated from a nonlinear equation approximates a linear relationship with Jw for a low permeability drug, regardless of whether or not Jw has a real effect on PeA. As such, a correlation between Jw and PeA is less meaningful as an indicator of a solvent drag effect. Moreover, from the linear relationship, the slope of the Jw-PeA correlation plot (defined as the sieving coefficient) equals the ratio of outflow versus inflow perfusate drug concentrations and can be greater than unity when more water than drug is absorbed during perfusion studies. The intercept of the correlation plot can be below zero if this occurs.

Body Water↗
PubMed2006

Water imaging (hydrography) in the fetus: the value of a heavily T2-weighted sequence.

BACKGROUND: Since the development of fast imaging sequences, MR has proved to be a helpful tool in the evaluation of fetal pathology. Because of the high water content of fetal tissues and pathology, hydrography imaging (MR fetography) can provide additional diagnostic information. OBJECTIVE: To demonstrate the benefit of MR fetography in fetal imaging. MATERIALS AND METHODS: From 2004 to 2005, 126 fetal MR examinations were performed for evaluation of an abnormality depicted on an antenatal sonogram. Single-shot fast spin-echo MR imaging and MR fetography were performed through the area of fetal pathology. The two studies were retrospectively compared. RESULTS: The primary diagnosis was not changed with the addition of MR fetography. New findings, particularly in the kidneys and spine, were identified in 9% of the patients. When fetal pathology was of high water content (80% patients), the MR fetography imaging increased diagnostic confidence. In 11% of the patients, those with cardiovascular or low water pathology, the MR fetography was not beneficial. CONCLUSION: The mainstay of fetal imaging is currently the HASTE and SSFSE sequences. However, MR fetography is an excellent adjunct that highlights fetal pathology by reinforcing the diagnosis, identifying additional findings, and providing high-contrast high-resolution images that are helpful when counseling clinicians and patients.

Body Water↗