Human Nutrition, study of how food affects the health and survival of the human body. Human beings
require food to grow, reproduce, and maintain good health. Without food, our bodies could not stay
warm, build or repair tissue, or maintain a heartbeat. Eating the right foods can help us avoid certain
diseases or recover faster when illness occurs. These and other important functions are fueled by
chemical substances in our food called nutrients. Nutrients are classified as carbohydrates, proteins,
fats, vitamins, minerals, and water.
When we eat a meal, nutrients are released from food through digestion. Digestion begins in the
mouth by the action of chewing and the chemical activity of saliva, a watery fluid that contains
enzymes, certain proteins that help break down food. Further digestion occurs as food travels through
the stomach and the small intestine, where digestive enzymes and acids liquefy food and muscle
contractions push it along the digestive tract. Nutrients are absorbed from the inside of the small
intestine into the bloodstream and carried to the sites in the body where they are needed. At these
sites, several chemical reactions occur that ensure the growth and function of body tissues. The parts
of foods that are not absorbed continue to move down the intestinal tract and are eliminated from the
body as feces.
Once digested, carbohydrates, proteins, and fats provide the body with the energy it needs to
maintain its many functions. Scientists measure this energy in kilocalories, the amount of energy
needed to raise 1 kilogram of water 1 degree Celsius. In nutrition discussions, scientists use the term
calorie instead of kilocalorie as the standard unit of measure in nutrition.
II ESSENTIAL NUTRIENTS
Nutrients are classified as essential or nonessential. Nonessential nutrients are manufactured in the
body and do not need to be obtained from food. Examples include cholesterol, a fatlike substance
present in all animal cells. Essential nutrients must be obtained from food sources, because the body
either does not produce them or produces them in amounts too small to maintain growth and health.
Essential nutrients include water, carbohydrates, proteins, fats, vitamins, and minerals.
An individual needs varying amounts of each essential nutrient, depending upon such factors as
gender and age. Specific health conditions, such as pregnancy, breast-feeding, illness, or drug use,
make unusual demands on the body and increase its need for nutrients. Dietary guidelines, which take
many of these factors into account, provide general guidance in meeting daily nutritional needs.
If the importance of a nutrient is judged by how long we can do without it, water ranks as the most
important. A person can survive only eight to ten days without water, whereas it takes weeks or even
months to die from a lack of food. Water circulates through our blood and lymphatic system,
transporting oxygen and nutrients to cells and removing wastes through urine and sweat. Water also
maintains the natural balance between dissolved salts and water inside and outside of cells. Our joints
and soft tissues depend on the cushioning that water provides for them. While water has no caloric
value and therefore is not an energy source, without it in our diets we could not digest or absorb the
foods we eat or eliminate the body’s digestive waste.
The human body is 65 percent water, and it takes an average of eight to ten cups to replenish the
water our bodies lose each day. How much water a person needs depends largely on the volume of
urine and sweat lost daily, and water needs are increased if a person suffers from diarrhea or vomiting
or undergoes heavy physical exercise. Water is replenished by drinking liquids, preferably those
without caffeine or alcohol, both of which increase the output of urine and thus dehydrate the body.
Many foods are also a good source of water—fruits and vegetables, for instance, are 80 to 95 percent
water; meats are made up of 50 percent water; and grains, such as oats and rice, can have as much
as 35 percent water.
Sources of Dietary Fiber
Vegetables, fruits, grains, and legumes constitute a rich source of dietary fiber. Composed of the indigestible cell
walls of plant material, fiber acts like a scouring pad to cleanse and flush the digestive tract. Researchers claim it
helps eliminate cancer-causing chemicals and may decrease the amount of cholesterol in the blood stream.
Charles D. Winters/Photo Researchers, Inc.
Carbohydrates are the human body’s key source of energy, providing 4 calories of energy per gram.
When carbohydrates are broken down by the body, the sugar glucose is produced; glucose is critical
to help maintain tissue protein, metabolize fat, and fuel the central nervous system.
Glucose is absorbed into the bloodstream through the intestinal wall. Some of this glucose goes
straight to work in our brain cells and red blood cells, while the rest makes its way to the liver and
muscles, where it is stored as glycogen (animal starch), and to fat cells, where it is stored as fat.
Glycogen is the body’s auxiliary energy source, tapped and converted back into glucose when we need
more energy. Although stored fat can also serve as a backup source of energy, it is never converted
into glucose. Fructose and galactose, other sugar products resulting from the breakdown of
carbohydrates, go straight to the liver, where they are converted into glucose.
Starches and sugars are the major carbohydrates. Common starch foods include whole-grain breads
and cereals, pasta, corn, beans, peas, and potatoes. Naturally occurring sugars are found in fruits and
many vegetables; milk products; and honey, maple sugar, and sugar cane. Foods that contain
starches and naturally occurring sugars are referred to as complex carbohydrates, because their
molecular complexity requires our bodies to break them down into a simpler form to obtain the much-
needed fuel, glucose. Our bodies digest and absorb complex carbohydrates at a rate that helps
maintain the healthful levels of glucose already in the blood.
Wheat grains must be ground into flour before they can be made into easily digestible foods such as pasta and
bread. Flour has played an important role in the diet of Western civilization since ancient times.
Blair Seitz/Photo Researchers, Inc.
In contrast, simple sugars, refined from naturally occurring sugars and added to processed foods,
require little digestion and are quickly absorbed by the body, triggering an unhealthy chain of events.
The body’s rapid absorption of simple sugars elevates the levels of glucose in the blood, which triggers
the release of the hormone insulin. Insulin reins in the body’s rising glucose levels, but at a price:
Glucose levels may fall so low within one to two hours after eating foods high in simple sugars, such
as candy, that the body responds by releasing chemicals known as anti-insulin hormones. This surge
in chemicals, the aftermath of eating a candy bar, can leave a person feeling irritable and nervous.
Many processed foods not only contain high levels of added simple sugars, they also tend to be high in
fat and lacking in the vitamins and minerals found naturally in complex carbohydrates. Nutritionists
often refer to such processed foods as junk foods and say that they provide only empty calories,
meaning they are loaded with calories from sugars and fats but lack the essential nutrients our bodies
In addition to starches and sugars, complex carbohydrates contain indigestible dietary fibers. Although
such fibers provide no energy or building materials, they play a vital role in our health. Found only in
plants, dietary fiber is classified as soluble or insoluble. Soluble fiber, found in such foods as oats,
barley, beans, peas, apples, strawberries, and citrus fruits, mixes with food in the stomach and
prevents or reduces the absorption by the small intestine of potentially dangerous substances from
food. Soluble fiber also binds dietary cholesterol and carries it out of the body, thus preventing it from
entering the bloodstream where it can accumulate in the inner walls of arteries and set the stage for
high blood pressure, heart disease, and strokes. Insoluble fiber, found in vegetables, whole-grain
products, and bran, provides roughage that speeds the elimination of feces, which decreases the time
that the body is exposed to harmful substances, possibly reducing the risk of colon cancer. Studies of
populations with fiber-rich diets, such as Africans and Asians, show that these populations have less
risk of colon cancer compared to those who eat low-fiber diets, such as Americans. In the United
States, colon cancer is the third most common cancer for both men and women, but experts believe
that, with a proper diet, it is one of the most preventable types of cancer.
Nutritionists caution that most Americans need to eat more complex carbohydrates. In the typical
American diet, only 40 to 50 percent of total calories come from carbohydrates—a lower percentage
than found in most of the world. To make matters worse, half of the carbohydrate calories consumed
by the typical American come from processed foods filled with simple sugars. Experts recommend that
these foods make up no more that 10 percent of our diet, because these foods offer no nutritional
value. Foods rich in complex carbohydrates, which provide vitamins, minerals, some protein, and
dietary fiber and are an abundant energy source, should make up roughly 50 percent of our daily
Dietary proteins are powerful compounds that build and repair body tissues, from hair and fingernails
to muscles. In addition to maintaining the body’s structure, proteins speed up chemical reactions in
the body, serve as chemical messengers, fight infection, and transport oxygen from the lungs to the
body’s tissues. Although protein provides 4 calories of energy per gram, the body uses protein for
energy only if carbohydrate and fat intake is insufficient. When tapped as an energy source, protein is
diverted from the many critical functions it performs for our bodies.
Proteins are made of smaller units called amino acids. Of the more than 20 amino acids our bodies
require, eight (nine in some older adults and young children) cannot be made by the body in sufficient
quantities to maintain health. These amino acids are considered essential and must be obtained from
food. When we eat food high in proteins, the digestive tract breaks this dietary protein into amino
acids. Absorbed into the bloodstream and sent to the cells that need them, amino acids then
recombine into the functional proteins our bodies need.
Animal proteins, found in such food as eggs, milk, meat, fish, and poultry, are considered complete
proteins because they contain all of the essential amino acids our bodies need. Plant proteins, found in
vegetables, grains, and beans, lack one or more of the essential amino acids. However, plant proteins
can be combined in the diet to provide all of the essential amino acids. A good example is rice and
beans. Each of these foods lacks one or more essential amino acids, but the amino acids missing in
rice are found in the beans, and vice versa. So when eaten together, these foods provide a complete
source of protein. Thus, people who do not eat animal products (see Vegetarianism) can meet their
protein needs with diets rich in grains, dried peas and beans, rice, nuts, and tofu, a soybean product.
Experts recommend that protein intake make up only 10 percent of our daily calorie intake. Some
people, especially in the United States and other developed countries, consume more protein than the
body needs. Because extra amino acids cannot be stored for later use, the body destroys these amino
acids and excretes their by-products. Alternatively, deficiencies in protein consumption, seen in the
diets of people in some developing nations, may result in health problems. Marasmus and
kwashiorkor, both life-threatening conditions, are the two most common forms of protein malnutrition.
Some health conditions, such as illness, stress, and pregnancy and breast-feeding in women, place an
enormous demand on the body as it builds tissue or fights infection, and these conditions require an
increase in protein consumption. For example, a healthy woman normally needs 45 grams of protein
each day. Experts recommend that a pregnant woman consume 55 grams of protein per day, and that
a breast-feeding mother consume 65 grams to maintain health.
A man of average size should eat 57 grams of protein daily. To support their rapid development,
infants and young children require relatively more protein than do adults. A three-month-old infant
requires about 13 grams of protein daily, and a four-year-old child requires about 22 grams. Once in
adolescence, sex hormone differences cause boys to develop more muscle and bone than girls; as a
result, the protein needs of adolescent boys are higher than those of girls.
Fats, which provide 9 calories of energy per gram, are the most concentrated of the energy-producing
nutrients, so our bodies need only very small amounts. Fats play an important role in building the
membranes that surround our cells and in helping blood to clot. Once digested and absorbed, fats help
the body absorb certain vitamins. Fat stored in the body cushions vital organs and protects us from
extreme cold and heat.
Fat consists of fatty acids attached to a substance called glycerol. Dietary fats are classified as
saturated, monounsaturated, and polyunsaturated according to the structure of their fatty acids.
Animal fats—from eggs, dairy products, and meats—are high in saturated fats and cholesterol, a
chemical substance found in all animal fat. Vegetable fats—found, for example, in avocados, olives,
some nuts, and certain vegetable oils—are rich in monounsaturated and polyunsaturated fat. As we
will see, high intake of saturated fats can be unhealthy.
To understand the problem with eating too much saturated fat, we must examine its relationship to
cholesterol. High levels of cholesterol in the blood have been linked to the development of heart
disease, strokes, and other health problems. Despite its bad reputation, our bodies need cholesterol,
which is used to build cell membranes, to protect nerve fibers, and to produce vitamin D and some
hormones, chemical messengers that help coordinate the body’s functions. We just do not need
cholesterol in our diet. The liver, and to a lesser extent the small intestine, manufacture all the
cholesterol we require. When we eat cholesterol from foods that contain saturated fatty acids, we
increase the level of a cholesterol-carrying substance in our blood that harms our health.
Cholesterol, like fat, is a lipid—an organic compound that is not soluble in water. In order to travel
through blood, cholesterol therefore must be transported through the body in special carriers, called
lipoproteins. High-density lipoproteins (HDLs) remove cholesterol from the walls of arteries, return it
to the liver, and help the liver excrete it as bile, a liquid acid essential to fat digestion. For this reason,
HDL is called “good” cholesterol.
Low-density lipoproteins (LDLs) and very-low-density lipoproteins (VLDLs) are considered “bad”
cholesterol. Both LDLs and VLDLs transport cholesterol from the liver to the cells. As they work, LDLs
and VLDLs leave plaque-forming cholesterol in the walls of the arteries, clogging the artery walls and
setting the stage for heart disease. Almost 70 percent of the cholesterol in our bodies is carried by
LDLs and VLDLs, and the remainder is transported by HDLs. For this reason, we need to consume
dietary fats that increase our HDLs and decrease our LDL and VLDL levels.
Saturated fatty acids—found in foods ranging from beef to ice cream, to mozzarella cheese to
doughnuts—should make up no more than 10 percent of a person’s total calorie intake each day.
Saturated fats are considered harmful to the heart and blood vessels because they are thought to
increase the level of LDLs and VLDLs and decrease the levels of HDLs.
Monounsaturated fats—found in olive, canola, and peanut oils—appear to have the best effect on
blood cholesterol, decreasing the level of LDLs and VLDLs and increasing the level of HDLs.
Polyunsaturated fats—found in margarine and sunflower, soybean, corn, and safflower oils—are
considered more healthful than saturated fats. However, if consumed in excess (more than 10 percent
of daily calories), they can decrease the blood levels of HDLs.
Most Americans obtain 15 to 50 percent of their daily calories from fats. Health experts consider diets
with more than 30 percent of calories from fat to be unsafe, increasing the risk of heart disease. High-
fat diets also contribute to obesity, which is linked to high blood pressure (see hypertension) and
diabetes mellitus. A diet high in both saturated and unsaturated fats has also been associated with
greater risk of developing cancers of the colon, prostate, breast, and uterus. Choosing a diet that is
low in fat and cholesterol is critical to maintaining health and reducing the risk of life-threatening
VII VITAMINS AND MINERALS
Both vitamins and minerals are needed by the body in very small amounts to trigger the thousands of
chemical reactions necessary to maintain good health. Many of these chemical reactions are linked,
with one triggering another. If there is a missing or deficient vitamin or mineral—or link—anywhere in
this chain, this process may break down, with potentially devastating health effects. Although similar
in supporting critical functions in the human body, vitamins and minerals have key differences.
Among their many functions, vitamins enhance the body’s use of carbohydrates, proteins, and fats.
They are critical in the formation of blood cells, hormones, nervous system chemicals known as
neurotransmitters, and the genetic material deoxyribonucleic acid (DNA). Vitamins are classified into
two groups: fat soluble and water soluble. Fat-soluble vitamins, which include vitamins A, D, E, and K,
are usually absorbed with the help of foods that contain fat. Fat containing these vitamins is broken
down by bile, a liquid released by the liver, and the body then absorbs the breakdown products and
vitamins. Excess amounts of fat-soluble vitamins are stored in the body’s fat, liver, and kidneys.
Because these vitamins can be stored in the body, they do not need to be consumed every day to
meet the body’s needs.
Water-soluble vitamins, which include vitamins C (also known as ascorbic acid), B1 (thiamine), B2
(riboflavin), B3 (niacin), B6, B12, and folic acid, cannot be stored and rapidly leave the body in urine if
taken in greater quantities than the body can use. Foods that contain water-soluble vitamins need to
be eaten daily to replenish the body’s needs.
In addition to the roles noted in the vitamin and mineral chart accompanying this article, vitamins A
(in the form of beta-carotene), C, and E function as antioxidants, which are vital in countering the
potential harm of chemicals known as free radicals. If these chemicals remain unchecked they can
make cells more vulnerable to cancer-causing substances. Free radicals can also transform chemicals
in the body into cancer-causing agents. Environmental pollutants, such as cigarette smoke, are
sources of free radicals.
Minerals are minute amounts of metallic elements that are vital for the healthy growth of teeth and
bones. They also help in such cellular activity as enzyme action, muscle contraction, nerve reaction,
and blood clotting. Mineral nutrients are classified as major elements (calcium, chlorine, magnesium,
phosphorus, potassium, sodium, and sulfur) and trace elements (chromium, copper, fluoride, iodine,
iron, selenium, and zinc).
Vitamins and minerals not only help the body perform its various functions, but also prevent the onset
of many disorders. For example, vitamin C is important in maintaining our bones and teeth; scurvy, a
disorder that attacks the gums, skin, and muscles, occurs in its absence. Diets lacking vitamin B1,
which supports neuromuscular function, can result in beriberi, a disease characterized by mental
confusion, muscle weakness, and inflammation of the heart. Adequate intake of folic acid by pregnant
women is critical to avoid nervous system defects in the developing fetus. The mineral calcium plays a
critical role in building and maintaining strong bones; without it, children develop weak bones and
adults experience the progressive loss of bone mass known as osteoporosis, which increases their risk
of bone fractures.
Vitamins and minerals are found in a wide variety of foods, but some foods are better sources of
specific vitamins and minerals than others. For example, oranges contain large amounts of vitamin C
and folic acid but very little of the other vitamins. Milk contains large amounts of calcium but no
vitamin C. Sweet potatoes are rich in vitamin A, but white potatoes contain almost none of this
vitamin. Because of these differences in vitamin and mineral content, it is wise to eat a wide variety of
VIII TOO LITTLE AND TOO MUCH FOOD
Somali Feeding Center
Foreign governments have established and stocked feeding centers in Somalia, such as the one pictured, in order
to help the Somali people overcome starvation. However, the country’s long-standing civil war has impeded
development and limited foreign assistance. Somalia’s rugged terrain and harsh climate allow for little arable land,
and the country has few natural resources. Serious droughts in the latter part of the 20th century have crippled the
country’s ability to produce food, while the influx of millions of refugees from Ethiopia has strained the nation’s
inadequate resources even further.
Bruce Brander/Photo Researchers, Inc.
When the body is not given enough of any one of the essential nutrients over a period of time, it
becomes weak and less able to fight infection. The brain may become sluggish and react slowly. The
body taps its stored fat for energy, and muscle is broken down to use for energy. Eventually the body
withers away, the heart ceases to pump properly, and death occurs—the most extreme result of a
dietary condition known as deficiency-related malnutrition.
Vitamin D Deficiency
Rickets can result from insufficient vitamin D in the diet or from insufficient amounts of ultraviolet radiation from
the sun. Rickets can lead to skeletal deformation, such as vertebral or leg curvature. This X ray reveals bone
deformation due to rickets.
Biophoto Associates/Science Source/Photo Researchers, Inc.
Deficiency diseases result from inadequate intake of the major nutrients. These deficiencies can result
from eating foods that lack critical vitamins and minerals, from a lack of variety of foods, or from
simply not having enough food. Malnutrition can reflect conditions of poverty, war, famine, and
disease. It can also result from eating disorders, such as anorexia nervosa and bulimia.
Although malnutrition is more commonly associated with dietary deficiencies, it also can develop in
cases where people have enough food to eat, but they choose foods low in essential nutrients. This is
the more common form of malnutrition in developed countries such as the United States. When poor
food choices are made, a person may be getting an adequate, or excessive, amount of calories each
day, yet still be undernourished. For example, iron deficiency is a common health problem among
women and young children in the United States, and low intake of calcium is directly related to poor
quality bones and increased fracture risk, especially in the elderly.
A diet of excesses may also lead to other nutritional problems. Obesity is the condition of having too
much body fat. It has been linked to life-threatening diseases including diabetes mellitus, heart
problems, and some forms of cancer. Eating too many salty foods may contribute to high blood
pressure (see hypertension), an often undiagnosed condition that causes the heart to work too hard
and puts strain on the arteries. High blood pressure can lead to strokes, heart attacks, and kidney
failure. A diet high in cholesterol and fat, particularly saturated fat, is the primary cause of
atherosclerosis, which results when fat and cholesterol deposits build up in the arteries, causing a
reduction in blood flow.
IX MAKING GOOD NUTRITIONAL CHOICES
USDA Food Pyramid
The United States Department of Agriculture Food Pyramid provides a practical visual guide to healthful eating,
indicating the recommended daily portions of the basic food groups.
© Microsoft Corporation. All Rights Reserved.
To determine healthful nutrition standards, the Food and Nutrition Board of the National Academy of
Sciences (NAS), a nonprofit, scholarly society that advises the United States government, periodically
assembles committees of national experts to update and assess nutrition guidelines. The NAS first
published its Recommended Dietary Allowances (RDAs) in 1941. An RDA reflects the amount of a
nutrient in the diet that should decrease the risk of chronic disease for most healthy individuals. The
NAS originally developed the RDAs to ensure that World War II soldiers stationed around the world
received enough of the right kinds of foods to maintain their health. The NAS periodically has updated
the RDAs to reflect new knowledge of nutrient needs.
In the late 1990s the NAS decided that the RDAs, originally developed to prevent nutrient deficiencies,
needed to serve instead as a guide for optimizing health. Consequently, the NAS created Dietary
Reference Intakes (DRIs), which incorporate the RDAs and a variety of new dietary guidelines. As part
of this change, the NAS replaced some RDAs with another measure, called Adequate Intake (AI).
Although the AI recommendations are often the same as those in the original RDA, use of this term
reflects that there is not enough scientific evidence to set a standard for the nutrient. Calcium, which
has an AI of 1,000 to 1,300 mg per day, is not an RDA because scientists do not yet know how much
calcium is needed to prevent osteoporosis.
Tolerable Upper Intake Level (UL) designates the highest recommended intake of a nutrient for good
health. If intake exceeds this amount, health problems may develop. Calcium, for instance, has a UL
of 2500 mg per day. Scientists know that more than this amount of calcium taken every day can
interfere with the absorption of iron, zinc, and magnesium and may result in kidney stones or kidney
Estimated Average Requirement (EAR) reflects the amount of a particular nutrient that meets the
optimal needs of half the individuals in a specified group. For example, the NAS cites an EAR of 45 to
90 grams of protein for men aged 18 to 25. This figure means that half the men in that population
need a daily intake of protein that falls within that range.
To simplify the complex standards established by the NAS, the United States Department of
Agriculture (USDA) created the Food Guide Pyramid, a visual display of the relative importance to
health of six food groups common to the American diet. The pyramid recommends a range of the
number of servings to choose from each group, based on the nutritional needs of males and females
and different age groups. In 2005 the pyramid was updated to accommodate different levels of
physical exercise and caloric intake resulting in 12 unique pyramids tailored to fit individual needs.
Nutrition Food Labels
Since 1994, the United States Food and Drug Administration and the Department of Agriculture have required
nearly all packaged food to carry a food label indicating the amounts of calories, vitamins, protein, fat, and fiber
per serving. This information is presented in a standardized format—including, for example, total fat in grams per
serving—to make it easy for consumers to use when making healthful diet choices.
Russell D. Curtis/Photo Researchers, Inc.
In an effort to provide additional nutritional guidance and reduce the incidence of diet-related cancers,
the National Cancer Institute developed the 5-a-Day Campaign for Better Health, a program that
promotes the practice of eating five to nine servings of fruits and vegetables daily. Studies of
populations that eat many fruits and vegetables reveal a decreased incidence of diet-related cancers.
Laboratory studies have shown that many fruits and vegetables contain phytochemicals, substances
that appear to limit the growth of cancer cells.
Many people obtain most of their nutrition information from a food label called the Nutrition Facts
panel. This label is mandatory for most foods that contain more than one ingredient, and these foods
are mostly processed foods. Labeling remains voluntary for raw meats, fresh fruits and vegetables,
foods produced by small businesses, and those sold in restaurants, food stands, and local bakeries.
The Nutrition Facts panel highlights a product’s content of fat, saturated fat, cholesterol, sodium,
dietary fiber, vitamins A and C, and the minerals calcium and iron. The stated content of these
nutrients must be based on a standard serving size, as defined by the Food and Drug Administration
(FDA). Food manufacturers may provide information about other nutrients if they choose. However, if
a nutritional claim is made on a product’s package, the appropriate nutrient content must be listed.
For example, if the package says “high in folic acid,” then the folic acid content in the product must be
given in the Nutrition Facts panel.
The Nutrition Facts panel also includes important information in a column headed % Daily Value (DV).
DVs tell how the food item meets the recommended daily intakes of fat, saturated fat, cholesterol,
carbohydrates, dietary fiber, and protein necessary for nutritional health based on the total intake
recommended for a person consuming 2,000 calories per day. One portion from a can of soup, for
example, may have less than 2 percent of the recommended daily value for cholesterol intake.
Health-conscious consumers can use the Nutrition Facts panel to guide their food choices. For
example, based on a daily diet of 2,000 calories, nutrition experts recommend that no more than 30
percent of those calories should be from fat, which would allow for a daily intake of around 65 grams
of fat. A Nutrition Facts panel may indicate that a serving of one brand of macaroni and cheese
contains 14 grams of fat, or a % DV of 25 percent. This tells the consumer that a serving of macaroni
and cheese provides about one-fourth of the suggested healthy level of daily fat intake. If another
brand of macaroni and cheese displays a % DRV of 10 percent fat, the nutrition-conscious consumer
would opt for this brand.
Nutritionists and other health experts help consumers make good food choices. People who study
nutrition in college may refer to themselves as nutritionists; often, however, the term refers to a
scientist who has pursued graduate education in this field. A nutritionist may also be a dietitian.
Dietitians are trained in nutrition, food chemistry, and diet planning. In the United States, dietitians
typically have graduated from a college program accredited by the American Dietetic Association
(ADA), completed an approved program of clinical experience, and passed the ADA’s registration
examination to earn the title Registered Dietitian (RD).