I looked it up. .. that news is even worse.
It appears that they want us to do closer to 10 a day? (More according to US heath authorities. wtf?)
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According to this "science?" They want us to drink fifteen cups a day. . .
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Water is essential for metabolism, substrate transport across membranes, cellular homeostasis, temperature regulation, and circulatory function. Although nutritional and physiological research teams and professional organizations have described the ...
www.ncbi.nlm.nih.gov
3. Why are Human Water Requirements Elusive?
"To maintain normal physiological functions (e.g.., blood pressure, pH, internal body temperature) and optimal health, and to deliver essential substances (e.g., oxygen, water, glucose, sodium, potassium) to cells, the CNS and neuroendocrine hormones act constantly to preserve internal homeostasis via a complex network of many organ and neural systems. Figure 1 presents several CNS-regulated variables which are relevant to body water balance. Each of these variables is simultaneously: (a) maintained (i.e., within the circulatory system or fluid compartments of the body) at a specific set point (e.g., a threshold beyond which the intensity of neuroendocrine responses increases ); and (b) constantly changing throughout the human life span in response to water and food intake, urine production, and non-renal water losses. Because of these fluctuations, human body water regulation is also dynamic. Therefore, we utilize the phrase dynamic complexity to refer to a constantly changing, vastly integrated regulatory mechanism [56]. This dynamic complexity is amplified by interconnected fluid compartments (i.e., intracellular, interstitial, extracellular, circulatory), organ systems (Table 3), neural plasticity (i.e., adaptations), and interactions of the physical processes (i.e., osmotic and oncotic pressure, simple diffusion, active transport) which govern water and electrolyte movements throughout the body."
This dynamic complexity (Table 3, Figure 1) represents the primary reason why the daily water requirements of humans have not been determined to this date (Table 1). We provide the following evidence in support of this statement:
- The relative influence of physiological processes which maintain water balance (Table 3) varies with different life scenarios. During sedentary daily activities in a mild environment, renal responses and thirst are the primary homeostatic regulators. During continuous-intermittent labor, or prolonged exercise at low intensities (5–18h duration), renal responses and thirst have minor-to-large effects on water regulation, whereas sweat loss presents the foremost challenge to homeostasis [56].
- Large between- and within-subject variances (i.e., of the variables in Table 3) make it difficult to determine a water requirement for all persons within a life stage (Table 1). As an example, Figure 2 illustrates the large between-subject variance of habitual TWI that exists in healthy young women (range, <1.0 to >4.5 L/24h) [13]. A large range of habitual TWI (0.6–5.2 L/24h) has also been reported for women during pregnancy [57]. Similarly, the third National Health and Nutrition Examination Survey [5] reported that the 1st decile and 10th decile of the mean TWI were 1.7–7.9 L/24h for men (n = 3,091) and 1.3–6.1 L/24h for women (n = 2,801). An example of large within-subject variability is also seen in the day-to-day differences of sweat losses that are experienced by athletes [24]. Total sweat loss during sedentary work activity (e.g., 8h of computer programming in an air-conditioned environment) may amount to <0.2 L/24h, whereas the total sweat volume during a 164-km ultradistance cycling event often exceeds 9 L during a 9-h ride [42]. . . "
https://www.ncbi.nlm.nih.gov/core/lw/2.0/html/tileshop_pmc/tileshop_pmc_inline.html?title=Click on image to zoom&p=PMC3&id=6315424_nutrients-10-01928-g002.jpg
(etc. . more egg head speck, you can click the link if you are interested. IOW, it is variable & elusive.)
