MODULE 1 |Portage Learning
STUDY NOTES:
ESSENTIALS IN NUTRITION
Good nutrition leads to a healthy life.
What is Nutrition?
Nutrition compared to other sciences is a fairly young science. New discoveries are constantly being made
and scientists and nutritionists are always evaluating ways in which nutrition impacts our lives. To begin we
need to understand what nutrition is. Nutrition by definition is the science that links foods to health and
disease. It includes the processes by which humans ingest, digest, absorb, transport and excrete food
substances. Nutrition spans all ages and impacts our well-being from conception to death. Good nutrition as
well as exercise is the key to good health.
When evaluating one’s health, there are actually five dimensions that can be evaluated, including physical
health, intellectual health, emotional health, social health and spiritual health.
Physical Health - ability of the body to perform daily functions for survival
Intellectual Health - the cognitive ability to learn and adapt
Emotional Health - the ability to express or suppress emotion
Social Health - ability to interact with others
Spiritual Health - purpose for human existence, cultural practices
Making good food choices and eating a variety of nutrients daily can contribute to a healthy life style.
What is the difference between food and nutrients? Food provides energy in terms of calories, nutrients are
substances found in food that provide the materials for building and maintaining body parts, regulators for
key metabolic processes and participate in metabolic reactions that provide energy to sustain life. The
science of nutrition provides the information consumers need to make wise food choices, evaluate the
amounts of nutrients required daily for one’s particular age and lifestyle, and make choices that may reduce
our risk of disease and contribute to longevity. Americans today have a much longer life expectancy than our
parents or grandparents. Making wise food choices to prevent disease throughout our lives is more
Page 1 of 28
,important today than ever before.
Why do we get hungry?
Many factors influence what we eat, when we eat and why we eat. However, basic physiological responses
play a major role in hunger and satiety. There are two drives that influence our desire to eat. One is hunger
and the other is appetite. Although both inform the body that it is time to eat, they are different mechanisms.
Hunger is the internal drive to find and eat food and is often experienced as a negative sensation such as
churning, growling or a painful sensation in the stomach. Appetite is the external drive that encourages us
to find and eat food and since it is related to pleasant sensations associated with food, it can lead us to eat
even if we are not hungry.
The hypothalamus is a region of the brain that plays a role in hunger as well as satiety and the feeling of
being full. When we have not eaten for a period of time, the amount of nutrients in the blood begin to
decline. This drop stimulates the feeding center in the hypothalamus which signals us to eat. When the
nutrient level of the blood begin to rise, the satiety center is activated and our desire to continue to eat
declines. This sounds like a simple process, but in reality the hypothalamus is constantly processing signals
from a variety of nerves throughout the body which influence our food intake. If a portion of the
hypothalamus is damaged or destroyed, from certain chemicals, trauma, surgery or cancers, the regulation
of hunger and satiety can be lost. In such an instance, the body no longer receives signals to stop eating
and weight gain is almost certain.
There are other factors that determine what we eat and the quantity of food we consume. The
gastrointestinal tract (GI) contributes to the feeling of satiety. The GI tract is the main site in the body used
for digestion and absorption of nutrients. The GI tract consists of the mouth, esophagus, stomach, small
intestine, large intestine rectum and anus. We will be studying the GI tract and its role in nutrition in a later
chapter.
Page 2 of 28
, The stomach plays a major role in satiety and weight regulation. As the stomach expands from food intake
and the nutrients consumed are absorbed, our desire to eat declines. A buffet meal is a good example of
how this takes place. As we proceed through the buffet line for the first time, most food looks very appetizing
and we often fill our plates with a variety of foods. On the second trip to the buffet, you are less likely to find
all the food appealing and make fewer choices. If more trips occur, the selection made is much narrower and
smaller in quantity. This is an example of the nerve network and the GI tract communicating with the brain
that your body no longer requires food. A meal that is high in fiber and water contributes to a greater feeling
of satiety.
Hormones also influence our feelings of hunger or satiety. Our body produces a variety of hormones that
work together to balance our hunger and satiety. Hormones are compounds secreted into the bloodstream
by one type of cell that acts to control the function of another type of cell. The list below outlines several
types of hormones related to hunger and satiety.
Hormones that increase hunger – Gherlin, Endorphins, Neuropeptide-Y
Hormones that decrease hunger (cause satiety) – Leptin, Serotonin, Cholecystokinin (CCK)
There are two key hormones in this process: Leptin and Ghrelin. Leptin is produced by the fat cells which
are also known as adipose tissue. The role of leptin is to alert the brain to turn off the hunger center and
activate the satiety center when consuming a meal. Ghrelin is produced by the stomach and has the
opposite role, travelling to the brain it stimulates the hunger center as it deactivates the satiety center. Ideally
they work together to balance hunger and satiety.
Problems arise when Leptin remains elevated for a period of time. This interferes with the hunger/satiety
balance and makes the satiety center insensitive to Leptin. Studies have found that obese individuals have
higher levels of Leptin than their peers. Scientists are now studying these hormones to see how they might
be used to treat obesity in the form of weight loss drugs.
Page 3 of 28
STUDY NOTES:
ESSENTIALS IN NUTRITION
Good nutrition leads to a healthy life.
What is Nutrition?
Nutrition compared to other sciences is a fairly young science. New discoveries are constantly being made
and scientists and nutritionists are always evaluating ways in which nutrition impacts our lives. To begin we
need to understand what nutrition is. Nutrition by definition is the science that links foods to health and
disease. It includes the processes by which humans ingest, digest, absorb, transport and excrete food
substances. Nutrition spans all ages and impacts our well-being from conception to death. Good nutrition as
well as exercise is the key to good health.
When evaluating one’s health, there are actually five dimensions that can be evaluated, including physical
health, intellectual health, emotional health, social health and spiritual health.
Physical Health - ability of the body to perform daily functions for survival
Intellectual Health - the cognitive ability to learn and adapt
Emotional Health - the ability to express or suppress emotion
Social Health - ability to interact with others
Spiritual Health - purpose for human existence, cultural practices
Making good food choices and eating a variety of nutrients daily can contribute to a healthy life style.
What is the difference between food and nutrients? Food provides energy in terms of calories, nutrients are
substances found in food that provide the materials for building and maintaining body parts, regulators for
key metabolic processes and participate in metabolic reactions that provide energy to sustain life. The
science of nutrition provides the information consumers need to make wise food choices, evaluate the
amounts of nutrients required daily for one’s particular age and lifestyle, and make choices that may reduce
our risk of disease and contribute to longevity. Americans today have a much longer life expectancy than our
parents or grandparents. Making wise food choices to prevent disease throughout our lives is more
Page 1 of 28
,important today than ever before.
Why do we get hungry?
Many factors influence what we eat, when we eat and why we eat. However, basic physiological responses
play a major role in hunger and satiety. There are two drives that influence our desire to eat. One is hunger
and the other is appetite. Although both inform the body that it is time to eat, they are different mechanisms.
Hunger is the internal drive to find and eat food and is often experienced as a negative sensation such as
churning, growling or a painful sensation in the stomach. Appetite is the external drive that encourages us
to find and eat food and since it is related to pleasant sensations associated with food, it can lead us to eat
even if we are not hungry.
The hypothalamus is a region of the brain that plays a role in hunger as well as satiety and the feeling of
being full. When we have not eaten for a period of time, the amount of nutrients in the blood begin to
decline. This drop stimulates the feeding center in the hypothalamus which signals us to eat. When the
nutrient level of the blood begin to rise, the satiety center is activated and our desire to continue to eat
declines. This sounds like a simple process, but in reality the hypothalamus is constantly processing signals
from a variety of nerves throughout the body which influence our food intake. If a portion of the
hypothalamus is damaged or destroyed, from certain chemicals, trauma, surgery or cancers, the regulation
of hunger and satiety can be lost. In such an instance, the body no longer receives signals to stop eating
and weight gain is almost certain.
There are other factors that determine what we eat and the quantity of food we consume. The
gastrointestinal tract (GI) contributes to the feeling of satiety. The GI tract is the main site in the body used
for digestion and absorption of nutrients. The GI tract consists of the mouth, esophagus, stomach, small
intestine, large intestine rectum and anus. We will be studying the GI tract and its role in nutrition in a later
chapter.
Page 2 of 28
, The stomach plays a major role in satiety and weight regulation. As the stomach expands from food intake
and the nutrients consumed are absorbed, our desire to eat declines. A buffet meal is a good example of
how this takes place. As we proceed through the buffet line for the first time, most food looks very appetizing
and we often fill our plates with a variety of foods. On the second trip to the buffet, you are less likely to find
all the food appealing and make fewer choices. If more trips occur, the selection made is much narrower and
smaller in quantity. This is an example of the nerve network and the GI tract communicating with the brain
that your body no longer requires food. A meal that is high in fiber and water contributes to a greater feeling
of satiety.
Hormones also influence our feelings of hunger or satiety. Our body produces a variety of hormones that
work together to balance our hunger and satiety. Hormones are compounds secreted into the bloodstream
by one type of cell that acts to control the function of another type of cell. The list below outlines several
types of hormones related to hunger and satiety.
Hormones that increase hunger – Gherlin, Endorphins, Neuropeptide-Y
Hormones that decrease hunger (cause satiety) – Leptin, Serotonin, Cholecystokinin (CCK)
There are two key hormones in this process: Leptin and Ghrelin. Leptin is produced by the fat cells which
are also known as adipose tissue. The role of leptin is to alert the brain to turn off the hunger center and
activate the satiety center when consuming a meal. Ghrelin is produced by the stomach and has the
opposite role, travelling to the brain it stimulates the hunger center as it deactivates the satiety center. Ideally
they work together to balance hunger and satiety.
Problems arise when Leptin remains elevated for a period of time. This interferes with the hunger/satiety
balance and makes the satiety center insensitive to Leptin. Studies have found that obese individuals have
higher levels of Leptin than their peers. Scientists are now studying these hormones to see how they might
be used to treat obesity in the form of weight loss drugs.
Page 3 of 28
