The osmoreceptors in the hypothalamus are sensitive to only certain solutes in the blood (e.g., sodium) but insensitive to others (e.g., urea).⁶ Thus, the osmoreceptors are not accurate gauges of blood solute concentration and water need at the cell level. The “thirst center” of the hypothalamus, triggered by osmosreceptor reaction to solute concentration, is distinct from the osmoreceptors.

Unfortunately for optimal hydration, the sense of thirst in the mouth (dryness) is quickly and easily satiated by small amounts of water, stimulating the moisture receptors within the mucous membranes of the mouth, throat, and upper gastrointestinal tract. Although thirst returns if the osmoreceptors and thirst center are not satiated, the body is caught in a game of catch-up that it can never win because it is never allowed to be in a continuous state of optimal hydration.

Sources of Water for the Body

Human beings derive their water intake from these basic sources:

• Beverages (70% to 80%)

• Foods with high water content (20% to 30%)

• Liberation of water molecules during oxidative metabolism of food sources ⁷

Water Losses from the Body

Water exits the body via several portals:

• Skin—insensible perspiration (450 mL daily in temperate climates). Of course elevations in body temperature can lead to massive increases in water losses in the form of sweat.

• Kidneys—1 to 2 L of urine daily. Water loss via urine increases during hyperglycemia (diabetes mellitus) as well as in disorders involving antidiuretic hormone (vasopressin).

• Respiratory mucous membranes—breath (250 to 350 mL daily). Additional water loss occurs during respiratory infections, which trigger increased discharge of mucous secretions.

• Digestive system, including feces (200 mL daily). Dramatic water losses arise from disorders whose symptoms include vomiting and/or diarrhea.

Perspiration is hypotonic; that is, it has lower electrolyte content than plasma or extracellular fluid. This phenomenon means that sweating leads to more water loss than electrolyte loss. As the electrolyte concentration in the extracellular fluid rises, it draws water out of cells (intracellular fluid), leading to cellular dehydration. This state of hypertonic dehydration demands replenishment with hypotonic beverages, such as pure water. Water need supersedes salt need during endurance exercise.⁸

Factors That Influence Water Need

Water intake requirements vary according to individual needs and circumstances. Some of the factors that affect water need are

• Physical activity/exercise

• Metabolism

• Diet

• Ambient atmospheric temperature

• Humidity

• Health status

Hydration for Athletes and Laborers

The National Athletic Trainers’ Association has published guidelines for athletic hydration. Here are some highlights of their recommendations that apply equally to “weekend warriors” and those involved in heavy physical labor ¹⁰:

• Establish hydration protocols, accommodating sweat rate, rest breaks, fluid access, environmental factors, acclimatization state, exercise duration and intensity, and personal preferences.

• Make fluid-replacement beverages easily accessible in individual containers to permit easier monitoring of fluid intake.

• Ensure that athletic activity begins in a well-hydrated state. Pre-exercise hydration entails consuming 500 to 600 mL (17 to 20 fl oz) of water 2 to 3 hours before exercise and 200 to 300 mL (7 to 10 fl oz) of water 10 to 20 minutes before exercise.

• Replace fluids sufficiently to meet sweat and urine losses and maintain hydration by preventing at less than 2% body weight reduction. This need requires 200 to 300 mL (7 to 10 fl oz) every 10 to 20 minutes.

• Hydrate postexercise to correct any fluid loss, ideally within 2 hours after exercise. When rehydration must be rapid, compensate for urine losses during rehydration by drinking 25% to 50% more than sweat losses to assure optimal rehydration 4 to 6 hours after exercise.

• Be alert for signs and symptoms of dehydration—thirst, irritability, general discomfort, followed by headache, weakness, dizziness, cramps, chills, vomiting, nausea, head or neck heat sensations, and decreased performance.

Pure Water versus Other Beverages

By definition, osmosis is the diffusion of water molecules from a place of relatively high concentration across a semipermeable membrane to a place of relatively low concentration. The amount of pressure that must be applied against this osmotic movement of water is called osmotic pressure. It is a measure of how vigorously water is attempting to cross the membrane. The differences in water concentration across membranes define the “water concentration gradient” across that membrane. Thus, the osmotic pressure is proportional to the concentration gradient. The higher the water concentration on one side of the membrane relative to the other side, the higher the osmotic pressure and the greater the vigor of movement of water molecules across the membrane. Any solutes dissolved in water outside the membrane decrease the water concentration gradient across the membrane and the vigor of water movement. If the concentration of solutes in the water outside the cell is less than the concentration of solutes within the cell, the concentration of water molecules will be greater outside the cell than within it. Therefore, water molecules will move by osmosis down their concentration gradient from the exterior to the interior and the cell will be hydrated.¹¹

Conversely, if the concentration of solutes is higher in the exterior than the interior, water molecules are in higher concentration within the cell. Therefore, water molecules will move down their concentration gradient from the interior to the exterior; thus the cell becomes dehydrated.

Obviously, the beverage that has the least amount of solutes and therefore the highest osmotic drive to hydrate the body down to the cellular level is pure water. If anything is dissolved in water (coffee, tea, sugar, flavorings, colors, protein, etc.), osmosis is reduced. Body and cell hydration are therefore inhibited by the consumption of beverages containing solutes. Thus the basic principles of physiology indicate that pure water is the beverage of choice for optimal hydration of the body.¹²

Water Temperature

According to the principles of traditional Chinese medicine, the consumption of cold food and drink is a bane of optimal health and wellness among Western people. The interior temperature of the body is higher than oral, axillary, or rectal temperature. For example, the interior temperature of the stomach is about 102° F and that of the heart is approximately 106° F. These warm temperatures are appropriate for the optimal physiologic functions and biochemical processes that sustain life. The ingestion of large amounts of cold food and beverages tends to inhibit these processes.

For this reason, it is prudent to ensure that water consumed is at room temperature or warmer.

Special Needs

Particular care must be taken to adequately hydrate people who, because of special circumstances, may need an even greater intake of water than recommended above. These persons include the following:

• Infants fed high-protein formulas (with caution not to overhydrate infants)

• Persons eating high-protein diets

• Patients suffering from disorders whose symptoms include fever, vomiting, diarrhea, respiratory discharges, and other types of water loss

• Patients taking diuretics

• People living in environments with high atmospheric temperatures

Physiology of Water Metabolism

Oxygen Transport

In the alveoli and in tissue capillaries and connective tissue, water is the medium in which gas exchange occurs. Without the ready solubility of oxygen and carbon dioxide in water, gas exchange in living systems would not be possible. Oxygen diffuses from atmospheric air into the water of alveolar tissues and plasma before it associates with hemoglobin in red blood cells. After being carried to peripheral tissue capillaries, oxygen dissociates from hemoglobin into the water of plasma and connective tissue. Water carries oxygen into the cell through membrane aquaporins.^13,¹⁴

Role of Water in Protein Structure and Function

The function of a protein is determined by its form—its three-dimensional shape. The unique sequence of amino acids, coded by human DNA, determines the shape or form of a protein. That sequence is determined by the sequence of the coding genes on chromosomal DNA that initiate the synthesis of that protein.¹⁵

Water molecules provide the environment that not only allows proteins to function but also supports their endeavors in unrecognized ways. In order to fulfill their respective missions, the amino acid strands of proteins must bend, twist, and contort their primary linear structure into secondary, tertiary, and quaternary forms. The hydrophobic and hydrophilic interactions between water and amino acid strands drive the conformational changes needed for proteins to realize their ultimate functional shapes. The final shape of a protein is determined by the manner in which water and amino acid strands are bonded to each other. As a lubricating agent, water facilitates the breaking and reestablishing of hydrogen bonds and other links between the various parts of protein. Once the appropriate bonding is in place, water molecules are critical to the continued integrity and stability of protein structure.¹⁶ It can therefore be suggested that the DNA genetic code is arranged in a fashion that specifically anticipates the conformational interaction of water molecules required to finish protein-generating tasks.^17,¹⁸

Cell Hydration and Cell Behavior

Because of the lack of routine techniques for measuring cell hydration and volume in patients, naturopaths and conventional practitioners alike often fail to consider cell hydration state during clinical assessment. This is an unfortunate oversight because of the effect of cell hydration state on the behavior of cells.

There is evidence that cell hydration state is an important determinant of protein and RNA turnover—anabolism and catabolism. It appears that hormones and amino acids modify protein turnover, partly by altering the cell hydration state, which alters cell volume. Changes in cell volume can serve as signals mediating hormone and amino acid effects, which control protein turnover. Increases in cell volume (swelling) inhibit protein catabolism and RNA degradation while stimulating the synthesis of protein, DNA, and RNA. Loss of cell volume (shrinkage) has the opposite effect on RNA, DNA, and protein. Consequently, cell swelling stimulates anabolic proliferative metabolism, while cell shrinkage has a catabolic and antiproliferative influence.^19,²⁰

In view of the protein catabolism that arises in disease states, researchers have proposed that cell shrinkage or loss of cellular volume caused by a loss of intracellular water volume, as is often seen in skeletal muscle and liver tissue, may be a common endpoint triggering protein catabolism in a variety of disease states.

Clinical Applications

Hydration and the Elderly

Dehydration is one of the most common causes of hospitalization among persons over the age of 65. It has been estimated that one half of those admitted for clinical dehydration die within a year of admission.

There are many factors leading to clinical and subclinical dehydration among seniors:

• Lower body water percentage

• Lack of awareness of hydration needs

• Lack of mental clarity and attentiveness to personal needs

• Illnesses that accelerate water loss by inducing vomiting, fever, and/or diarrhea

• Decline of thirst sensation with age

Gradual total body dehydration is a hallmark of the aging process. In addition, the preponderance of body water shifts gradually with age from cell interiors to the exterior connective tissue. Even death itself is frequently linked to dehydration. Long-term chronic disease eventually wears the body down to the point where patients can no longer ingest water and food, ultimately succumbing to dehydration.

To make matters worse, our sense of thirst declines with age. Researchers have concluded that after water deprivation, “there is a deficit in thirst and water intake in healthy elderly men, as compared with younger men.” This is true despite the fact that the antidiuretic hormone response is maintained.²¹

Chronic “subclinical” dehydration (or “hypohydration”) contributes to the aging process. In its struggle for survival, the body shifts precious resources away from processes that increase longevity toward those needed for short-term survival.

Winter Hydration

The human body loses water in many ways during winter. Some are obvious; others are not:

• Exercising in cold weather mutes the experience of sweating in many people, deceiving them into thinking that their bodies are not losing much water.

• Cold air cannot hold as much moisture as warm air. Therefore winter air is drier than summer air. The drier air draws more water from the lungs as we breathe, so we exhale more moisture during winter months.

• Interior environments are usually very dry in the winter because of the use of dehumidifying heating methods. The decreased interior humidity increases water loss from the lungs and skin.

• When the body gets chilled, blood is shifted away from the periphery toward the interior organs to preserve vital heat. The shunting of blood to the interior increases renal arterial flow, glomerular filtration rate, and urine output. This effect is called cold diuresis.

• Cold weather increases body metabolism and the associated water needs required to maintain healthy body temperature.

• Respiratory illnesses of winter cause the body to generate large amounts of mucus in order to dispose of pathogens. The water in these discharges must be replaced.

• Intestinal influenza, with diarrhea and vomiting, requires additional water and perhaps electrolyte replacement.

Dehydration and Jet Lag

The cabin atmospheric pressure of modern passenger jets is equivalent to that found on land at an elevation of 8000 ft above sea level. Although the relative humidity of the Sahara Desert is typically 20% to 25%, the humidity of jet cabin air can be as dry as 1% to 10%. For these reasons, dehydration is a major factor in the experience of jet lag. People should keep thoroughly hydrated with pure water and avoid the other beverages offered by flight attendants. It is prudent to drink at least 8 ounces of pure water per hour.

Effect of Hydration State on Blood Flow

Whole-blood viscosity has been identified as an independent risk factor for atherosclerosis and cardiovascular events. The most dangerous time of day for heart attack is the last period of sleep and the first few hours in the morning after awakening. A number of factors may play a role in this trend; hydration state may be one of them. Overnight fasting from fluid intake increases blood viscosity and adversely affects blood flow (rheology) to major organs. Consumption of 200 mL of water under these circumstances helps normalize blood flow to major organs.²²

Cognitive-Motor Function and Hydration State

In young adults, neither cognitive-motor function nor neurophysiologic function differs between people under water deprivation and controls. On the other hand, subjective ratings of mental performance during water deprivation point to increased fatigue as well as impaired alertness and the concentration needed to complete tasks. Healthy people tend to employ compensating mechanisms for increased fatigue and reduced alertness. Test of reaction time reveal significant gender differences in the response to dehydration. Water deprivation induces a prolonged reaction time in women but a shortened one in men.²³

Multiple-Organ-System Effects of Chronic Subclinical Dehydration

The insidious effects of chronic hypohydration are wide ranging and staggering. Consider the following effects:

• Disintegration of cellular structure

• Impaired flow of nutrients into the cell due to compromised membrane protein channels and insufficient carrier solvent (water)

• Local tissue resistance to endocrine hormones due to faulty integrity and responsiveness of membrane receptors

• Chronic fatigue due to lack of enzyme-catalyzed energy production ²⁴

• Free radical damage to cell structures, including DNA, due to reduced enzymatic free radical scavenging

• Inadequate repair of nuclear DNA damage due to faulty enzyme repair activity

• Reduced production of key bioactive compounds, such as hormones, digestive enzymes, neurotransmitters, etc.

• Accumulation of toxins within cells

• Increased synthesis of histamine within the central nervous system ²⁵

• Chronically elevated levels of antidiuretic hormone (vasopressin)

• Chronically elevated levels of cortisol, with adverse effects on bone integrity, muscle mass, connective tissue, blood pressure, and immunity ²

Subclinical Dehydration (Hypohydration): The Missing Diagnosis

Water cures nothing except dehydration. However, once dehydration has been corrected at the cellular level, healing is possible. This is because hypohydration at the cellular level is a major contributing factor to many ailments. Based on years of research with inmates of an Iranian prison, Dr. Fereydoon Batmanghelidj has proposed a new paradigm of disease and healing. It states that the suffering associated with many disorders is triggered or worsened by dehydration.

The reason for this effect is that, under the stress of dehydration, the body takes desperate measures to conserve water. Part of this effort involves the synthesis and release of histamine. It appears that histamine release activates other systems designed to save body water. Antidiuretic hormone decreases water loss in urine. Histamine and kinin compounds influence the escape of water from capillaries into connective tissue. Decreasing blood water content decreases blood volume and increases plasma sodium concentration, activating the renin-angiotensin system and vasopressin to elevate blood pressure.^4,^5,²⁶

A key concept of Dr. Batmanghelidj’s new paradigm is based on his years of clinical observation and practice with only the simplest crude healing tools at his disposal. He writes, “Chronic cellular dehydration painfully and prematurely kills. Its initial outward manifestations have until now been labeled as diseases of unknown origin.”

Recurrent noninfectious conditions associated with pain and discomfort in various parts of the body, which cannot be explained by other identifiable causes, can be interpreted as expressions of water deficits at the sites of the tissue manifesting symptoms.^4,²⁷

Common Conditions Improved by Water

On the basis of empiric experience, the scope of application of water as a therapeutic tool is immense. The only caveat is that kidney filtration must be intact and healthy to allow the excretion of water and accompanying toxins. The following is a list of disorders in which water therapy is indicated:

A few of these are considered in more detail below.

Coronary Heart Disease and Fatal Myocardial Infarction

It has been known for some time that high blood and plasma viscosity, high hematocrit, and high blood concentrations of fibrinogen are correlated with coronary heart disease and atherosclerosis. Remarkably, even high “normal” levels of these parameters are considered independent risk factors.^16,^24,²⁶^–³³ These factors have also been linked to intermittent claudication.³¹ High hematocrit has been associated with tachycardia, the magnitude of heart tissue damage from myocardial infarction, reduced oxygen transport, and reduced blood supply to heart tissue.

Based on this evidence, researchers at the Heart Institute of Loma Linda University analyzed lifestyle data to determine what influence the consumption of pure water and other beverages would have on the risk of fatal heart attack.

Compared with those who drank two or fewer glasses of pure water daily, men who drank five or more had only 46% of the risk of having a fatal heart attack and women had only 59% of the risk. Even more remarkable, compared with those who drank two or fewer glasses of fluids other than pure water (e.g., tea, soft drink, juice, etc.), women who drank five or more had 147% greater risk and men had 46% greater risk. Moreover, these relative risk relationships held regardless of adjustments for any other factors. In essence, the consumption of pure water decreases the risk of fatal heart attack; consumption of other beverages increases the risk.²⁵

According to the researchers, failing to drink enough water can be as harmful to heart health as smoking. Just by increasing pure water intake, one can reduce the risk of death from heart attack by one half. This amount of benefit is greater than that gained by ceasing smoking, reducing cholesterol, exercising, or maintaining ideal body weight. Thus, increasing one’s intake of pure water could be the cheapest and simplest method of reducing fatal heart attack risk imaginable.

Peptic Ulcers and Dyspepsia

These conditions were the first that brought hidden, subclinical dehydration to the attention of Dr. Batmanghelidj in the Iranian prison. Thousands of cases successfully treated with water therapy lend credence to this modality. Chronic inflammation of the stomach and duodenum, with heartburn and acid reflux, are prime indications for water intervention. The concept here is not farfetched when the function of the intestinal organs is understood. The gastrointestinal mucous membranes must produce sufficient mucus to protect themselves from damage from digestive acid and enzymes. All of these secretions are water-based. Hypohydration inhibits both digestion and membrane protection. In addition, water deficits reduce the volume of bicarbonate-containing fluids released from the pancreas. This deficit results in a failure to properly neutralize stomach acid, leading to duodenal ulcers.³⁴

Asthma and Allergies

Histamine is a prime mediator of allergy and asthma. It is generated in the central nervous system when the body is dehydrated. It is also released by mast cells located on the mucous membranes of the respiratory and gastrointestinal tracts. Histamine works with the immune system, facilitating the movement of white blood cells to sites of microbial invasion.

Of particular note is the new scientific light being shed on exercise-induced asthma. Studies indicate that dehydration during exercise can increase the intensity of asthma symptoms in persons subject to asthmatic attacks. Dehydration can increase spasms of the bronchial smooth muscle because of overly dry airway membranes. Dehydration of mucous membranes occurs before the asthmatic athlete even begins training. Dehydrated asthmatics begin exercise with reduced hydration capacity; therefore, a pathologic respiratory state occurs more rapidly. Researchers have concluded that “Exercise induced asthma is an exaggerated airway response to airway dehydration.” Airway narrowing from exercise in elite athletes and otherwise healthy subjects is now considered a physiologic response to pathologic changes in airway cells resulting from “dehydration injury.”³⁵ These changes also occur in healthy subjects exercising intensely for long periods and breathing cold air, dry air, or both.³⁶

In order to minimize the risk of asthmatic attacks during exercise, it is imperative for the athlete to be in a state of optimal hydration before training begins and for good hydration status to be maintained throughout the exercise and during recovery. Pure water can be a very dear friend to an asthmatic.

As with allergies and asthma, histamine is believed to be a contributing factor in migraine headache.³⁷ Hypohydration induces the central nervous system to increase its synthesis of histamine. Thus, optimal hydration should minimize histamine synthesis as well as associated migraine headache. Anecdotal clinical evidence is mounting in support of pure water as a helpful adjunct to other natural approaches.

References

1. Meyerowitz S. Water: The Ultimate Cure. Summertown, TN: Book Publishing Co; 2001. 7

2. Wang Z., Deurenberg P., Wang W., et al. Hydration of fat-free body mass: review and critique of a classic body-composition constant. Am J Clin Nutr. 1999 May;69(5):833–841.

3. Jéquier E., Constant F. Water as an essential nutrient: the physiological basis of hydration. Eur J Clin Nutr. 2010 Feb;64(2):115–123. Epub 2009 Sep 2

4. Häussinger D. The role of cellular hydration in the regulation of cell function. Biochem J. 1996 Feb 1;313(Pt 3):697–710.

5. Szinnai G., Schachinger H., Arnaud M.J., et al. Effect of water deprivation on cognitive-motor performance in healthy men and women. Am J Physiol Regul Integr Comp Physiol. 2005 Jul;289(1):R275–R280. Epub 2005 Apr 21

6. Berne R.M., Levy M.N. Principles of Physiology, 3rd ed., St. Louis: Mosby, Inc; 2000:4–18. 434-454

7. European Food Safety Journal. Draft Dietary reference values for water. Scientific Opinion of the Panel on Dietetic Products, Nutrition and Allergies. 2008:1–49.

8. Sawka M.N., Cheuvront S.N., Carter R., III. Human water needs. Nutr Rev. 2005 Jun;63(6 Pt 2):S30–S39.

9. Dietary Reference Intakes: Electrolytes and water. DRI table for sodium, chloride, potassium, inorganic sulfate and water. Washington, DC: National Academy of Sciences. Institute of Medicine. Food and Nutrition Board; 2004.

10. Case D.J., et al. National Athletic Trainers’ Association Position Statement: Fluid replacement for athletes. J Athl Train. 2000;35(2):212–224.

11. Berne R.M., Levy M.N. Principles of Physiology, 3rd ed., St. Louis: Mosby, Inc; 2000:10.