CHAPTER 8 WATER Section.pptx

Nutrition & You
Sixth Edition
Chapter 8 Lecture
Water Section of the
Chapter
Copyright © 2023 Pearson Education, Inc. All Rights Reserved

Learning Outcomes for Chapter 8
8.1 Explain the importance and functions of water in the
body.
8.2 Describe water balance and how the body maintains it.
8.3 Identify daily water needs and the best sources for it.

Why Is Water So Important? (1 of 2)
• Water is the most abundant substance in body.
– Average healthy adult is about 60 percent water.
▪ Muscle tissue is 75 percent water, fat up to 20
percent.
– Can survive only a few days without water
– Water is balanced among fluid compartments.
▪ Intracellular fluids: inside cells
▪ Extracellular fluids: interstitial fluid between cells
and fluid in the blood
– Electrolytes: minerals that help maintain fluid balance

Figure 8.1 Your Body Is Mostly Water

Figure 8.2 Water as Part of Body Fluids

Why Is Water So Important? (2 of 2)
• Acts as universal solvent and transport medium
– Medium for chemical reactions in body
– As part of blood, helps transport oxygen, nutrients, and
hormones to cells
– As part of interstitial fluid, helps transport waste
products away from cells for excretion
• Helps maintain body temperature
• Lubricant for joints, eyes; part of mucus and saliva
• Protective cushion for brain, organs, and fetus

Figure 8.3 Water Helps Regulate Your
Body Temperature

What Is Water Balance, and How Do
You Maintain It?
• Water balance: water consumed = water lost
• You take in water through beverages and food
• You lose water through your kidneys (as urine), large
intestine, lungs, and skin
– Insensible water loss: through evaporation from skin
and when you exhale
– Sensible water loss: through urine, feces, and sweat

Figure 8.4 The Concept of Water
Balance: Intake Equals Output

Losing Too Much Water Can Cause
Dehydration (1 of 2)
• Dehydration can result from inadequate water intake or too
much water loss from diarrhea, vomiting, high fever, or use
of diuretics.
• Your thirst mechanism signals dehydration:
– Dry mouth due to increased electrolyte concentration in
blood: less water available to make saliva
– Blood volume decreases, sodium concentration
increases in blood:
▪ Brain triggers thirst mechanism and secretion of
antidiuretic hormone (ADH) to reduce urine output
▪ Fluid inside cells moves into blood by osmosis

Figure 8.5 A Simple Demonstration of
Osmosis

Losing Too Much Water Can Cause
Dehydration (2 of 2)
• Other ways to tell if you're dehydrated:
– Cornerstone method: measure body weight before and
after exercise
▪ Weight loss = water loss
– Monitor urine color
▪ Color darkens with concentration, indicating water
loss

Figure 8.6 Urine Color Can Signal
Dehydration

Consuming Too Much Water Can
Cause Hyponatremia
• Hyponatremia is a condition of too little sodium in the
blood
• For healthy individuals who consume a balanced diet, it
is difficult to consume too much water
• However, some individuals have experienced water
toxicity
– For example, soldiers in training and endurance
athletes

Figure 8.7 Fluid Balance During
Exercise

How Much Water Do You Need and
What Are the Best Sources?
• Daily water needs depend on physical activity,
environmental factors, and diet.
• Recommendations based on reported total water intake of
healthy Americans
• Men: 16 cups/day (about 13 cups of beverages)
• Women: 12 cups/day (about 9 cups of beverages)
– About 80 percent from beverages, 20 percent from
foods
– Physical activity increases needs.

Figure 8.8 Water Content of Foods

Figure 8.9 The Best Way to Meet Your
Daily Water Needs
1
Includes diet soft drinks and tea or coffee with sugar substitutes.
2
Includes fat-tree or 1 % milk and unsweetened fortified soy milk.

Nutrition in the Real World: Tap Water
or Bottled Water: Is Bottled Better?
• False assumption: bottled water is purer than tap water
• Tap water is perfectly safe.
– Monitored by Environmental Protection Agency (EPA)
– Provides fluoride and helps prevent dental caries
• Bottled water is very popular
– Most products conform to FDA requirements
– May actually be tap water
– High cost
– Various "designer" waters on the market

A Well of Sources for Bottled Water
Mineral water Water derived from an underground source that contains a
specific amount of naturally occurring minerals and trace
elements. The minerals and elements cannot be added to the
water after bottling.
Spring water Water that is obtained from underground water that flows
naturally to the surface. The water is collected at the spring or
at the site of the well purposefully drilled to obtain this water.
Sparkling
water
Spring water that has carbon dioxide gas added to supply
“bubbles” before bottling. Also sold as seltzer water or club
soda. Note: This is technically considered a soft drink and does
not have to adhere to FDA bottled water regulations.
Distilled water Water that has been boiled and processed to remove most, but
not all, contaminants.
Flavored water Water that has a flavor such as lemon or lime added. It may
also contain added sugars and calories.
Vitamin or
enhanced
waters
Water that has vitamins, protein, herbs, and/or caffeine added
to it. Such water may also contain added sugars and calories.
Water can be classified according to its source or how it is treated prior to bottling.

Bottled Versus Tap Water: A Summary
Bottled Water Tap Water
Cost to Consumers Cost to Consumers
• About $1.00–$4.00 per gallon (plain water) • About $0.003 per gallon
• Designer waters can cost more than $10
per gallon and may contain added sugar
and calories
Blank
Safety and Sustainability Safety and Sustainability
• Generally safe • Municipal water is regulated by EPA, state,
and local regulations
• Regulated by the FDA • EPA guidelines require that the public have
access to water quality reports and be
notified if water quality is outside
established bounds
• May not contain fluoride
Blank
• If not recycled, end up as garbage in
landfills
Blank
Benefits to Consumers Benefits to Consumers
• Packaging of bottled water may make it
more convenient than tap water
• Available at the faucet
Blank
• Often contains fluoride, which helps to
prevent tooth decay
• May taste better than tap water • Doesn’t contain any added sugar or calories

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