Myth As part of a healthy diet, peopleneed to take dietary supplements.

~ Where do you thinkmost teens get their informationabout nutrition? How factual do youthink their information is?

Fact A diet that contains a varietyof healthful foods usually supplies allthe vitamins and minerals that yourbody needs.

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Vocabulary• vitamin• antioxidant• mineral

• anemia• homeostasis

• electrolyte

• dehydration

Section 2

Objectives~ Identify the two main

classes of vitamins.

~ List seven minerals yourbody needs in significantamounts.

~ Explain why water is soimportant to your body.

VitaminsYou're I?robably aware that vitamins are important for your body andhealth, but where do they come from? What do they do? And how many

different kinds do you need?

One of the first discoveries of the importance of vitamins came in the

1700s. Sailors on long voyages survived on hard, dry biscuits, salted meat,

and not much else. Because of their limited diet, many sailors developed

a serious disease called scurvy. People with scurvy suffer from bleeding

gums, stiff joints, and sores that do not heal.A Scottish doctor, James Lind, discovered that sailors who were fed

citrus fruits recovered from scurvy. Today, health scientists know that

scurvy is caused by a lack of vitamin C,which is found in abundance in citrus

fruits. After Lind made his discov­

ery, sailors were provided with

oranges, lemons, and limes. The

word limey, a British slang termfor sailor, comes from the limes

that sailors ate to ward off scurvy.

202 Chapter 8

1What Are Vitamins? Nutrients that are made by living things, are

required only in small amounts, and that assist many chemical reactions

in the body are vitamins. Unlike carbohydrates, fats, and proteins, vita­

mins do not directly provide you with energy or the raw materials of

which your cells are made. Instead, vitamins help the body with various

processes, including the use of other nutrients. Vitamins also play roles in

various chemical reactions in the body. For example, vitamin K helps your

blood clot when you get a cut or a scrape.Your body is able to make some vitamins. For example, your skin

manufactures vitamin D when it is exposed to sunlight. However, most

vitamins must be supplied in the food you eat. There are two classes of

vitamins: fat -soluble vitamins, which dissolve in fatty materials, andwater-soluble vitamins, which dissolve in water.

For: Updates on nutrientsVisit: www.SciLinks.org/healthWeb Code: ctn-3082

Fat-Soluble Vitamins Fat-soluble vitamins-vitamins A, D, E, and

K-occur in vegetable oils, liver, eggs, and certain vegetables. Figure 7 out­lines the food sources and functions of each fat-soluble vitamin.

Fat-soluble vitamins can be stored by the body. The absorption of fat­

soluble vitamins by the digestive system is enhanced by dietary fat. Some

indigestible fat substitutes that are used in low-fat or low-calorie productscan prevent absorption of these vitamins. To prevent this from happen­

ing, extra vitamins, particularly vitamins A and D, are often added to

foods prepared with fat substitutes.

Vitamin Good Sources

Food and Nutrition 203

FIGURE 7 Fat-soluble vitamins are

found in many dietary sources andhave important functions.

Aids in blood clotting

Aids in maintenance of red bloodcells, vitamin A, and fats

Maintains bones and teeth;helps in the use of calciumand phosphorus

Maintains healthy skin, bones, teeth,and hair; aids vision in dim light

Green, leafy vegetables;potatoes; liver; madeby intestinal bacteria

Margarine; vegetable oils; wheat germ; wholegrains; legumes; green, leafy vegetables

Milk; eggs; liver;exposure of skin to sunlight

Liver; eggs; cheese; milk; yellow, orange,and dark green vegetables and fruit

E

K

A

D

'J!mmII:7 Name three foods you eat regularly that supply

YOUR LlFE/ vitamin A.

Fat-Soluble Vitamins

Water-Soluble Vitamins Water-soluble vitamins-includ­

ing vitamin C and all of the B vitamins-are found in fruits,

vegetables, and other sources. Unlike the fat-soluble vitamins, water­

soluble vitamins cannot be stored by the body. Therefore, it is

important to eat foods that supply them every day. Figure 8 outlinesthe food sources and functions of the water-soluble vitamins.

Water-Soluble Vitamins

Main FunctionsGood SourcesVitamin

81(Thiamin)

Pork products; liver; whole-grainfoods; legumes

Aids in carbohydrate use andnervous system function

82(Riboflavin)

Milk; eggs; meat; whole grains;dark green vegetables

Aids in metabolism of

carbohydrates, proteins, and fats

83(Niacin)

Poultry; meat; fish; wholegrains; nuts

Aids in metabolism

86

(Pyroxidine)

812(Cobalamin)

Pantothenic acid

Folate(Folic acid)

8iotin

Meat; poultry; fish; whole-grainfoods; green vegetables

Meat; fish; poultry; ( -eggs; milk; cheese \.

Organ meats; poultry; ( •••. "fish; eggs; grains : \. "-.,.,-, .Green, leafy vegetables;legumes

Organ meats; poultry; fish; eggs;peas; bananas; melons

Aids in metabolism of carbohydrates,proteins, and fats

Maintains healthy nervoussystem and red blood cells

Aids in metabolism

Aids in formation of red

blood cells and protein

Aids in metabolism

FIGURE 8 Water-soluble vitamins

are found in many food sources.Reading Tables Which vitaminsaid in metabolism?

C

(Ascorbic acid)Citrus fruits; green vegetables;melons; potatoes; tomatoes

Aids in bone, teeth, and skin formation;resistance to infection; iron uptake

204 Chapter 8

Antioxidants Vitamins called antioxidants help protecthealthy cellsfrom the damage caused by the normal aging processas well as from certain types of cancer. Vitamins C and E are twoof the most powerful antioxidants. Sources of vitamin C includecitrus fruits, strawberries, broccoli, tomatoes, and potatoes.Sources of vitamin. E include vegetable oils, whole grains, seeds,nuts, and peanut butter.

MineralsYour body requires only small amounts of minerals, which arenutrients that occur naturally in rocks and soil. Plants absorbminerals from rocks and soil through their roots. Animals obtainthese nutrients by either eating the plants or eating animals thathave eaten the plants.

Twenty-four different minerals have been shown to be essen­tial for good health. Youneed seven minerals-calcium, sodium,potassium, magnesium, phosphorus, chlorine, and sulfur-insignificant amounts. Youneed only trace amounts of others, suchas iron, fluorine, iodine, copper, and zinc. Minerals perform awide variety of functions in the body.

Calcium Some minerals are of special nutritional concern.For example, many people's diets do not include enoughcalcium. Calcium is important in blood clotting and thefunctioning of your nervous system. It is an essential ingre­dient in the formation and maintenance of bones and teeth.

Milk and other dairy products are good sources of calcium, butmany people cannot digest dairy products. Beet greens, collardgreens,broccoli, and tofu are also good sources of calcium.

A lack of calcium can sometimes lead to osteoporosis, a con­dition in which the bones gradually weaken. Osteoporosis isusually a disease of older people, but your calcium intake duringadolescence can help you build stronger bones now to avoidosteoporosis later in life. Osteoporosis will be discussed inChapter II.

~ What are you doing now to preventYOUR LlFE/ osteoporosis in the future?

FIGURE 9 Calcium is essential for

building the strong bones you need toplay sports now and to maintain bonestrength as you age.

85010 It

girls~not~'·enough calcium

Food and Nutrition 205

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FIGURE 10 You can limit

sodium by making your ownsnacks instead of eatingprocessed foods or fast foods.

206 Chapter 8

Potassium Potassium and sodium work together to maintain water

balance in the body. In addition, people who consume enough potassium

each day generally have lower blood pressure than people who do not.

The problem is that most Americans do not consume enough potassium.

Foods that are rich in potassium include baked potatoes, spinach,

bananas, dried fruits, oranges, soybeans, and tomato products.

Iron Iron is necessary for healthy red blood cells. These cells have an

iron-containing substance called hemoglobin, which carries oxygen from

your lungs to all parts of your body. Adolescent girls and adult women

need extra iron, because they lose iron during menstruation. Both adoles­

cent girls and boys also need iron to build muscle mass.

There are many good sources of iron. During one day, for example,

you might fulfill your iron requirements by eating an iron-fortified break­

fast cereal, a salad containing garbanzo beans, a serving of cooked spinach,

several dried apricots, and a serving oflean beef. If a person's diet does not

include enough iron, he or she may develop anemia (uh NEE me uh), a

condition in which the red blood cells do not contain enough hemoglo­

bin. People suffering from anemia are often weak and tired, and they may

become sick easily.

Sodium In contrast to calcium, most people consume far more

sodium than they need. Table salt, or sodium chloride, is a major source

of this mineral. So are some processed, or manufactured, foods, such as

canned soups and frozen pizza. Salty snack foods, including chips and

salted nuts, are also high in sodium.Sodium is important in several body processes, including the func­

tioninp of the heart and water balance. However, too much sodium cancause a problem with blood pressure. People who have high blood pres­sure should reduce their salt intake because an excess of sodium can raise

their blood pressure levels.

~ Find out the sodium content of a snack

YOUR LlFE/ that you ate today.

FIGURE 11 Minerals are found in a variety offoods and perform many essential functions in thebody. Reading Tables Which minerals aid in thefunction of the nervous system?

Minerals

Mineral

Calcium

Phosphorus

Magnesium

Sodium

Chlorine

Pot~ssium

Sulfur

Iodine

Selenium

Iron

Zinc

Fluorine

Good Sources

Milk and milk products; dark green,leafy vegetables; tofu; legumes

Meat; eggs; poultry; fish; legumes;milk and milk products

Leafy green vegetables; legumes;nuts; whole-grain food

Table salt; processed food;soy sauce

Table salt; soy sauce; processed foods

Vegetables, fruits, meat, poultry, fish

Milk and milk products; meat;poultry; fish; legumes; nuts

Seafood; iodized salt

Seafoods; meats; organ meat

Red meats; seafood; legumes; green,leafy vegetables; fortified cereals;dried fruits

Meats; poultry; seafood; milk;whole-grain foods

Fish; fluoridated water

Main Functions \

Helps build and maintain bones and teeth;nerve and muscle function; blood clotting

Helps build and maintain bones andteeth; energy metabolism

Helps build bones and protein; energymetabolism; muscle contraction

Helps maintain water balance;nerve function

Helps maintain water balance; digestion

Helps maintain water balance and makeprotein; functioning of heart and nervous system

Forms part of some amino acids andB vitamins

Helps in metabolism as part ofthyroid hormone

Helps break down harmful substances

Part of red blood cells;

helps in energy metabolism

Part of many substances thathelp carry out body processes

Helps form strongteeth and bones

Food and Nutrition 207

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FIGURE 12 Salad bars loaded with

fresh vegetables are a great way toget all the vitamins and mineralsyou need without takingsupplements.

208 Chapter 8

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Vitamin and MineralSupplements

If a person does not get enough of a specific nutrient,a nutrient deficiency can occur. People who eat a wide

variety of healthy foods, however, seldom suffer fromnutrient deficiencies. Vitamin and mineral supplements,

therefore, are not usually necessary if your diet is nutri-tious and well-balanced. In fact, an excess, or overdose, of

vitamins or minerals may damage your health. Somecommon symptoms of overdose include nausea, vomiting,

diarrhea, and rash.

If you want to boost your intake of a particular vitamin ormineral, first consider how to meet your needs by making

small adjustments to your daily diet. For example, if you needto increase your calcium intake, consider eating yogurt as a

snack, or drinking milk with dinner instead of a soft drink.If you do take a vitamin or mineral supplement, take one that

meets, but does not exceed, your needs. A health care providercan advise you about how much is the right amount. Beware of

megadosing, or taking in larger amounts of a nutrient than yourbody needs. For fat-soluble vitamins, the excess amounts would be

stored in body fat and can cause vitamin poisoning. Symptoms ofvitamin poisoning include nausea, vomiting, joint pain, severe

headaches, and hair loss. For water-soluble vitamins, on the other

hand, the excess amount would be excreted by your body. Therefore,taking megadoses of these vitamins may not be a wise investment.

WaterAbout 65 percent of your body weight is water. You do not get energyfrom this nutrient directly. Nevertheless, water is essential for all lifeprocesses, including the production of energy. Nearly all of the body'schemical reactions, including those that produce energy and build newtissues, take place in a water solution. Water is the primary componentof blood and tissue. It carries dissolved waste products out of the bodyand helps digest food.

Water and Homeostasis Homeostasis (ho mee oh STAY sis) is

the process of maintaining a steady state inside your body. What rolesdoes water play in homeostasis?

~ When you become overheated, your body excretes perspiration,which cools your body. Thus, water regulates body temperature.

~ Water contains dissolved substances called electrolytes that regulatemany processes in your cells.For example, your nervous and muscu­lar systems depend on electrolytes, such as sodium and potassium.

Preventing Dehydration Very heavy perspiring or severe diar­

rhea can result in dehydration (dee hy DRAY shun), a serious reduction in

the body's water content. When the body becomes dehydrated, it loses

important electrolytes a\ong with the water. Symptoms of dehy-dration can include weakness, rapid breathing, and a weak

heartbeat. Whenever your body loses a lot of water, youneed to be careful to increase your water intake to

prevent dehydration.

How Much Water? Every day, you need at

least ten 8-ounce cups of water if you are a female

14 to 18 years old. Males in the same age group

need 14 cups of water per day. This water can bein the form of foods that contain a lot of water,

such as fruits and vegetables, or juices. Drinks that

contain caffeine-coffee, tea, and some sodas-may

not be good sources of water for your body. This is

because caffeine increases the amount of water your body

excretes, at least at first. It is probably better to obtain water fromfoods that don't contain caffeine.

Water Versus Sports Drinks Experts in the field of sports med­

icine recommend that you drink about 2 cups of fluid 2 hours before

exercise. During exercise, take a drink about every 15 minutes. Are sports,drinks a better choice than water? A sports drink is not necessary if you

exercise for 60 minutes or less. If you exercise longer, a sports drink that

contains carbohydrates may be beneficial. However, sports drinks with

electrolytes are not necessary unless you exercise for 5 hours or more.

••..~:.)4CUPSIt

._.\'1.

exercise.

FIGURE 13 It is important to drinkplenty of water every day.

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Section 2 Review_/Key Ideas and Vocabulary1. What are vitamins? How do they differ from

minerals?

2. What are the two classes of vitamins? Whichvitamins fall into each class?

3. Which seven minerals are needed by the body insignificant amounts?

4. What roles does water play in the body?5. Define homeostasis.

Critical Thinking6. Classifying What vitamins are supplied by green,

leafy vegetables? By citrus fruits?

Fluorine and the Water Supply Find outwhether your community adds fluorine to itswater supply. If possible, talk to a town official,dentist, or other knowledgeable adult in yourcommunity. Write a paragraph summarizing

your findings. ~

7. Applying C~ncepts What are some ways thatpeople with high blood pressure can reduce theirsodium intake?

8. Relating Cause and Effect Explain how feelings ofthirst can help a person maintain homeostasis on ahot day.

Food and Nutrition 209