Ch. 11 Water

Daily Beverage Recommendations

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Recommendations

80 percent intake from beverages and 20 percent from food. Adult women: approximately 9 cups of fluid per day. Adult men: approximately 13 cups of fluid per day. People who are very active have higher water requirements. Drink bottled or tap water, milk, and 100% juices throughout the day. Most foods can also contribute to meeting daily water needs. Fruits and vegetables can be 70 percent or more water by weight.

Osmosis

Affects the movement of water between cells, not the solutes, Water moves from a diluted concentration to a high concentration of electrolytes, Osmotic pressure controls the directional flow of water, Based on osmolality or the concentration of particles in a solution (number of solutes)

Distribution depends on:

Age, Percent of water declines with age, Gender, Males have more body water than females, Composition of fat and muscle, Muscle is ~65 percent water, Fat is 10 to 40 percent water.

Proteins regulate fluid balance

Albumin in the vascular space attracts fluid from the interstitial spaces.

Do Diuretics Like Caffeine and Alcohol Affect Water Balance?

Alcoholic drinks, regular coffee, and tea contribute to total water intake. Alcohol and caffeine are considered diuretics. Contribute to water loss

Sources of Body Water Include Beverages and Food

Beverages are the largest source. All foods contain some water. Fruits and vegetables contain the most. Grains contain the least.

Renin Helps the Body Reabsorb Water and Salts

Blood pressure falls or sodium concentration is reduced. Renin is secreted by the kidneys (Enzyme splits off a protein called angiotensin I from the protein angiotensinogen found in the blood). In the lungs angiotensin I is converted to angiotensin II.

ADH Helps Stimulate Fluid Intake and Reduce Urine Output

Blood volume drops, Hypothalamus detects decrease in blood pressure and increase in concentration of salt, Thirst mechanism and fluid intake are stimulated, Hypothalamus stimulates pituitary glands to release ADH, ADH stimulates the kidneys to reabsorb water and decrease urine output, Blood volume increases and osmolality returns to normal.

Water Is Balanced between Fluid Compartments

Body fluid is located-In intracellular fluid (ICF) - within the cells.Contains potassium, proteins, various acids In extracellular fluid (ECF) - outside the cells-Contains sodium chloride and sodium bicarbonate solutions

During digestion water hydrolyzes the bonds of:

Carbohydrate molecules, Protein molecules, Fat molecules. Water is formed and released when smaller molecules join together during condensation.

Renin-angiotensin system adapts to changes in dietary sodium intake

Consume too little sodium, Osmolality drops in extracellular fluid (ECF), Fluid shifts from the blood to the interstitial fluid, Blood volume and blood pressure decrease, Angiotensin II triggers the adrenal glands to release aldosterone.

Consuming Too Little Water Is a Common Problem

Dehydration can be caused by: Inadequate water intake, Losing excessive amounts of water due to diarrhea, vomiting, high fever, or use of diuretics, As little as a 2 percent loss of body water can trigger:Loss of short-term and long-term memory, Lower attention span and cognition, Reduced ability to maintain core temperature, Increased risk of urinary tract infections and fatigue. Consequences of dehydration can be severe for children, elderly, and athletes. Elderly: misdiagnosed as dementia Athletes: impairs performance

Tolerance to diuretic effects develops over time

Does not negatively affect hydration status

Mild diuretic that blocks the action of ADH in the kidneys

Does not result in dehydration

Electrolytes Participate in Fluid Balance

Electrolytes-Minerals with charged ions that conduct electrical current -Potassium, Phosphate, Magnesium, Calcium, Chloride, Sodium Electrolytes maintain water balance between compartments.

How Is Water Balance Maintained?

Fluid balance (homeostasis), Is necessary for normal reactions within the cells, Body adapts to changes in water intake and losses.

Water

H2O

How Do Water and Sodium Affect Blood Pressure?

If the body retains too much fluid, blood volume increases and blood pressure will likely rise. Kidneys regulate blood volume and electrolyte balance. Three hormones and one enzyme control blood volume. Hormones (Antidiuretic hormone (ADH), also called vasopressin, Angiotensin, Aldosterone, Enzyme (Renin)

Consume 16 fluid ounces for every pound lost.

If weight gain is noted, overhydration is likely. Consume less fluid before the next activity.

Alcohol Can Be Dehydrating

Interferes with water balance by inhibiting ADH, Can induce urination as quickly as 20 minutes after consumption, Is dehydrating, Affects electrolyte concentration, especially potassium, Older drinkers are less affected than younger drinkers.

Two types of ECF

Interstitial fluids: bathe the outside of cells. Intravascular fluids: in blood and lymph

Angiotensin II

Is a powerful vasoconstrictor, Stimulates the kidneys to reabsorb water and salts, Stimulates adrenal glands to release aldosterone. Aldosterone Helps Stimulate Sodium Reabsorption.

Lubricant for:

Joints, sensitive eye tissues, mouth, and intestinal tract

The sodium-potassium pump

Maintains normal electrolyte concentrations, Water is attracted to sodium and moves toward it, Two Na+ ions are exchanged for three K+ ions, Keeps the cell from swelling and bursting, Aids in electrical conduction in nerve and muscle cells, Aids in nutrient absorption

Water Is Excreted through the Kidneys, Large Intestine, Lungs, and Skin

Majority of fluid is excreted through the kidneys as urine. Urine production is dependent on water intake. Water is lost through intestinal fluids in the stool. Plant fibers can reduce excretion. Diarrhea and vomiting can increase excretion. Evaporated through exhalation and through the skin. Insensible water loss. Losses through sweat. Varies based on (Environmental factors, Temperature, Humidity, Wind, Sun's intensity, Clothing worn, Amount of physical activity.

The Thirst Mechanism

Monitor Water Intake to Avoid Overhydration and Dehydration

Water is a polar molecule.

Neutral electrical charge, Maintains acid-base balance

First line of treatment for hypertension

Often pharmaceutical diuretics, Promote diuresis by inhibiting the reabsorption of sodium, Increased sodium excretion increases fluid excretion. Reduces blood volume and lowers blood pressure, Some diuretics increase potassium loss and the risk of hypokalemia, Consuming Too Much Water Can Cause Hyponatremia.

Provides a protective cushion

Protects organs and Bathes certain organs with fluid

Water intoxication

Rare in healthy individuals who consume a balanced diet, as more urine will be produced. Drinking fluid too fast without adequate sodium replacement depletes sodium and increases the rate of urine production. Results in hyponatremia, Can cause swelling in the brain, Symptoms include fatigue, confusion, and disorientation.

To prevent dehydration

Reduce alcohol consumption. Drink water after consuming alcohol.

Hypotension if severe enough

Reduced cardiac output, Impaired digestion, Fainting or blackout

Aldosterone

Signals kidneys to retain more sodium, Indirectly leads to water retention

An average healthy adult is 45 to 75 percent water.

True

Blood Volume Regulates Blood Pressure

True

Caffeine Does Not Cause Significant Loss of Body Water

True

Caffeine doesn't cause a significant loss of body water over the course of the day compared with noncaffeinated beverages.

True

Diuretic Medications Can Help Treat Hypertension

True

During pregnancy the fetus is surrounded by watery amniotic fluid.

True

Fluids move between ECF and ICF easily.

True

Look at urine color to assess hydration.

True

Overconsumption can upset fluid balance.

True

Sodium has the greatest effect on fluid balance.

True

These sources contribute to an average daily intake of 2,550 ml (about 2 quarts).

True

Water Is a Universal Solvent

True

The Functions of Water in the Body

Universal solvent: liquid in which substances dissolve, Polarity attracts charged particles into a solution that dissolves proteins, glucose, and some minerals. Important to digestion. Helps transport dissolved nutrients and other substances throughout the body. Transports oxygen, nutrients, and hormones to cells. Transports waste products away from cells for excretion in urine and stool. Maintains body temperature. Absorbs and releases heat generated by the body. Provides structure to cells. Participates in hydrolysis and condensation reactions

Water balance

Water consumed = water excreted

Metabolism

Water generated during metabolism is metabolic water.

During dehydration

Water is depleted from ECF and ICF

Thirst is often the first physical sign of dehydration.

Water is lost from the body. Reduced blood volume Reduced blood pressure.

Why Is Water Essential to Life?

Water is the most abundant substance in the body.

Plays a role in acid-base balance

Water is used to reduce or increase pH levels. Breaks down or forms carbonic acid

How Much Water Do You Need and What Are the Best Sources?

Water needs depend on: Physical activity, Environmental factors, Diet

Measure body weight before and after long bouts of vigorous physical activity or labor and note changes.

Weight loss after an activity is due to loss of body water.

Anions

negative charge

Cations

positive charge