Nutrition e5 Chapter 12

Chapter

12 Water and Major Minerals

Water: The Essential Ingredients for Life • Water makes up 45–75 percent of a person’s weight.

Photo: © Piotr Marcinski/ShutterStock, Inc.

Functions of Water

Electrolytes and Water: A Delicate Equilibrium • Cation (positively charged ions) • Anions (negatively charged ions)

Water in the Body • Major fluid compartments • Intracellular fluid • Extracellular fluid • Interstitial fluid • Plasma

Water in the Body • Sodiumpotassium pump • Semipermeable membrane • Osmosis

Intake Recommendations: How Much Water Is Enough?

• Adequate intake includes drinking water, beverages, and food • Recommendations are higher for • Pregnancy • Lactation • Athletes and active people

• Sports drinks and water absorption

Intake Recommendations: How Much Water Is Enough?

• Water Excretion: Where Does the Water Go? • Insensible water losses

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Intake Recommendations: How Much Water Is Enough?

• Water Balance • • • •

Regulation of fluid excretion Regulation of blood volume and pressure Thirst Water reabsorption in the GI tract

Intake Recommendations: How Much Water Is Enough?

• Alcohol, caffeine, and common medications affect fluid balance • Dehydration • Water intoxication

Intake Recommendations: How Much Water Is Enough?

• Water Balance • Regulation of Blood Volume and Pressure • Renin, angiotensin I, angiotensinogen, angiotensin II, adlosterone • Thirst • Water reabsorption in the GI tract

Intake Recommendations: How Much Water Is Enough? • Alcohol, caffeine, and common medications affect fluid balance

Major Minerals • Minerals in foods • Bioavailabiltiy

Sodium • Functions • Fluid balance • Nerve impulse transmission

• Dietary recommendations • Food sources and recommended intake • Salt • Processed and convenience foods • Limit to 2,300 milligrams/day (DV)

• Hyponatremia • Hypernatremia • Hypertension

Potassium • Functions • Muscle contraction • Nerve impulse transmission • Fluid balance

• Dietary recommendations • Food sources • Unprocessed foods: fruits, vegetables, grains

• Hypokalemia • Hyperkalemia

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Chloride • Functions of chloride • Fluid balance • Hydrochloric acid (stomach acid)

• Dietary recommendations • Food sources of chloride • Table salt

• Hypochloremia

Calcium • Functions • • • • •

Bone structure Nerve function Blood clotting Muscle contraction Cellular metabolism

Regulation of Blood Calcium • Hormones • Vitamin D • Parathyroid hormone • Calcitonin

• Target tissues • Small intestine • Kidneys • Bone

Calcium • Dietary recommendations for calcium • Food sources • Milk and dairy products • Green vegetables, tofu, fortified foods

• • • •

Calcium absorption Hypocalcemia Hypercalcemia Osteoporosis

Phosphorus • Functions • Bone structure • Component of ATP, DNA, RNA, phospholipids

• Dietary recommendations • Food sources • Meat, milk, eggs • Processed foods

• Hypophosphatemia • Hyperphosphatemia

Magnesium • Functions • DNA and protein synthesis • Blood clotting, muscle contraction, ATP production

• Dietary recommendations • Food sources • Whole grains, vegetables, legumes, tofu, seafood

• Hypomagnesemia • Hypermagnesemia

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Sulfur • Not used only as a nutrient • A component of organic compounds • Important in protein sturcture

Major Minerals and Health • Hypertension • High blood pressure

• Osteoporosis • “Porous bone” • Is the leading cause of bone fractures in older adults

Water Content of Various Foods • As you might expect, crunchy vegetables contain more water than dry cereal. • But did you know that potatoes contain a high percentage of water?

Sports Drinks and Water Absorption • Drinking plenty of plain water and eating a healthful diet easily replaces the fluid and electrolytes a person loses during moderate exercise in pleasant weather.

But if you are involved in endurance activities or strenuous exercise in hot weather, consider using sports drinks instead of just plain water. • Sports drinks contain glucose and electrolytes that improve the taste, help maintain blood glucose levels, and enhance absorption.

Calcium • Calcium is a major component of bones and teeth. In addition, calcium is required for muscle contraction, nerve impulse transmission, blood clotting, and regulation of cell metabolism. • For adults,1,000 milligrams per day is recommended, and more is suggested for adolescents and older adults.

Dairy foods and fortified foods are major dietary sources of calcium. • Calcium status is regulated by three hormones that control intestinal absorption, bone calcium release, and kidney excretion: calcitriol, parathyroid hormone, and calcitonin. Lack of dietary calcium contributes to the development of osteoporosis.

Water Intoxication • Because drinking fluids temporarily alleviates thirst, we rarely drink to the point of overhydration and dilution of body fluids. However, replacement of fluid losses following intensive or prolonged exercise with plain water (and no electrolytes) can result in overhydration and hyponatremia (low blood sodium) in athletes.

• Acute water toxicity has been reported due to rapid consumption of large quantities of fluids that greatly exceeded the kidney’s maximal excretion rate of approximately 0.7 to 1.0 liters per hour.

• Several years ago, some dieters overenthusiastically followed a fad weight reduction diet calling for massive water intake and suffered seizures from overhydration.

Dietary Guidelines for Americans • Consume less than 2,300 mg (approximately 1 teaspoon of salt) of sodium per day.

• Choose and prepare foods with little salt. At the same time, consume potassium-rich foods, such as fruits and vegetables.

• Key recommendations for specific population groups: individuals with hypertension, blacks, and middleaged and older adults. Aim to consume no more than 1,500 mg of sodium per day, and meet the potassium recommendation (4,700 mg/day) with food.

Sources of Dietary Sodium

Banana Facts • You may know that bananas are high in potassium, but did you also know that they have an unusually high-carbohydrate content? • Before ripening, a banana is almost entirely starch. After ripening, certain varieties are almost entirely sugar—as much as 20 percent by weight.

Food Sources of Potassium Š Photodisc

Effects of Progressive Dehydration • Dehydration, or too little water, is a major killer worldwide—infants and the frail elderly are especially vulnerable.

• Gastrointestinal infections are primarily responsible.

• Dehydration diminishes physical and mental performance.