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6671 Samenvatting Voedingsleer - The Science Of Nutrition
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Samenvatting the Science of NutritionChapter 1 The Science of Nutrition: Linking Food, Function, and Health
What is the science of nutrition and how did it evolve?
Food: the plants and animals we consume. It contains the energy and nutrients our body needs to
maintain life and support growth and health.
Nutrition: the science that studies food and how food nourishes our body and influences our health.
It identifies the processes by which we consume, digest, metabolize, and store the nutrients in foods
and how these nutrients affect our body. Nutrition also involves studying the factors that influence our
eating patterns, making recommendations about the amount we should eat of each type of food,
maintaining food safety, and addressing issues related to the production of food and the global food
supply.
Chronic disease: a disease characterized by a gradual onset and long duration, with signs and
symptoms that are difficult to interpret and that respond poorly to medical treatment (e.g. obesity,
cardiovascular disease, diabetes, various cancers).
How does nutrition contribute to health?
Traditionally defined as the absence of disease, wellness is now considered to be an active process
that we work on every day. We focus on two closely related aspects of wellness: nutrition and physical
activity.
Prevalence: the percentage of the population that is affected with a particular disease at a given
time.
There are a range of personal, social, economic and environmental factors (also referred to as
determinants) that influence our health. Five broad categories of determinants of health include
biology and genetics, individual behavior, social factors, health services, and policymaking. The four
overarching goals are to: 1) attain high-quality, longer lives free of preventable disease, disability,
injury, and premature death; 2) achieve health equity, eliminate disparities, and improve the health of
all groups; 3) create social and physical environments that promote good health for all; and 4)
promote quality of life, healthy development, and healthy behaviors across all life stages.
What are nutrients?
The six groups of nutrients found in food are:
● Carbohydrates
● Lipids (including fats and oils)
● Proteins
● Vitamins
● Minerals
● Water
The term organic is commonly used to describe foods that are grown with little or no use of chemicals.
But when scientists describe individual nutrients as organic, they mean that these nutrients contain
the elements carbon and hydrogen, which are essential components of all living organisms.
Carbohydrates, lipids, proteins, and vitamins are organic. Minerals and water are inorganic.
Carbohydrates, lipids and proteins are the only nutrients in foods that provide energy. By this we
mean that these nutrients break down and reassemble into a fuel that the body uses to support
physical activity and basic physiologic functioning. Along with water, the energy nutrients are also
referred to as macronutrients. See focus figure 1.3 on p. 10.
The energy in foods is measured in units called kilocalories (kcal). A kilocalorie is the amount of heat
required to raise the temperature of 1 kilogram of water by 1 degree Celsius. We can say that the
energy found in 1 gram of carbohydrate is equal to 4 kcal. kilo- is a prefix used in the metric system to
indicate 1000. Technically, 1 kilocalorie is equal to 1000 calories. A kilocalorie is also sometimes
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,referred to as a large calorie or as a Calorie, written with a capital C. We use the term energy when
referring to the general concept of energy intake or expenditure. We use the term kilocalories (kcal)
when discussing units of energy. We use the term Calories with a capital C when presenting
information about foods and food labels. Both carbohydrates and proteins provide 4 kcal per gram,
alcohol provides 7 kcal per gram, and fats provide 9 kcal per gram.
Carbohydrates are the primary source of fuel for the human body, particularly for neurologic
functioning and physical exercise. A close look at the word carbohydrate reveals the chemical
structure of this nutrient. Carbo- refers to carbon, and -hydrate refers to water. Thus, carbohydrates
are composed of chains of carbon, hydrogen, and oxygen. Fiber is also classified as a type of
carbohydrate.
Lipids are another important source of energy for the body. Lipids are a diverse group of organic
substances that are largely insoluble in water. In foods, they are found in solid fats and liquid oils.
Lipids include triglycerides, phospholipids, and sterols. Like carbohydrates, lipids are composed
mainly of carbon, hydrogen, and oxygen. However, they contain proportionately much less oxygen
and water than do carbohydrates. This quality partly explains why they yield more energy per gram
than either carbohydrates or proteins. Triglycerides (more commonly known as fats) are by far the
most common lipid in foods. They are composed of an alcohol molecule called glycerol attached to
three acid molecules called fatty acids. Triglycerides are an important energy source when we are at
rest and during low- to moderate-intensity exercise. The human body is capable of storing large
amounts of triglycerides as adipose tissue, or body fat. These fat stores can be broken down for energy
during periods of fasting, such as while we are asleep. Foods that contain lipids are also important for
the absorption of fat-soluble vitamins. Phospholipids are a type of lipid that contains phosphate. The
body synthesizes phospholipids, and they are found in a few foods. Cholesterol is a form of lipid that is
synthesized in the liver and other body tissues.
Proteins also contain carbon, hydrogen, and oxygen, but they differ from carbohydrates and lipids in
that they contain the element nitrogen. Within proteins, these four elements assemble into small
building blocks known as amino acids. We break down dietary proteins into amino acids and
reassemble them to build our own body proteins - for instance, the proteins in muscle and blood.
Although proteins can provide energy, they are not usually a primary energy source. Proteins play a
major role in building, repairing, and maintaining cells and tissues, and assisting in regulating
metabolism and fluid balance.
Vitamins and minerals are referred to as micronutrients. That’s because we need relatively small
amounts of these nutrients to support normal health and body functions. Vitamins are organic
compounds that assist in the regulation of the body’s physiologic processes. Contrary to popular
belief, vitamins do not contain energy; however, they are essential to energy metabolism, the
process by which the macronutrients are broken down into the smaller chemicals that our body can
absorb and use. So vitamins assist with releasing and using energy in carbohdyrates, fats, and
proteins. They are also critical in building and maintaining healthy bone, blood, and muscle; in
supporting our immune system so we can fight illness and disease; and in ensuring healthy vision.
Vitamins are classified as either fat soluble or water soluble. This classification reflects how vitamins
are absorbed, transported, and stored in our body.
Minerals include sodium, calcium, iron, and over a dozen more. They are classified as inorganic
because they do not contain carbon and hydrogen. In fact, they do not “contain” other substances at
all. Minerals are single elements, so they already exist in the simplest possible chemical form. All
minerals maintain their structure no matter what environment they are in. Minerals have many
important physiologic functions. They assist in fluid regulation and energy production, are essential to
the health of our bones and blood, and help rid the body of harmful by-products of metabolism. The
two categories of minerals in our diet and body are the major minerals and the trace minerals.
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, Adequate water intake ensures the proper balance of fluid both inside and outside our cells and assists
in the regulation of nerve impulses and body temperature, muscle contractions, nutrient transport,
and excretion of waste products.
You may have seen the term functional foods; these are foods with biologically active ingredients that
provide health benefits beyond those provided by their nutrients. Common examples are probiotic
foods such as yoghurt and fermented vegetables, which contain beneficial bacteria. Many functional
foods contain non-nutrient plant compounds that are beneficial to our health. These are called
phytochemicals.
What are the current dietary intake recommendations and how are they used?
Dietary Reference Intakes (DRI’s): dietary standards for healthy people. The first step nutrition
researchers take in determining a population’s nutrient requirements is to calculate the Estimated
Average Requirement (EAR). The EAR represents the average daily nutrient intake level
estimated to meet the requirement of half of the healthy individuals in a particular life stage or gender
group. Scientists use this to define the RDA for a given nutrient. Recommended Dietary
Allowance (RDA): The average daily nutrient intake level that meets the nutrient requirements of
97% to 98% of healthy individuals in a particular life stage and gender group. If an EAR cannot be
determined for a nutrient, then this nutrient cannot have an RDA. When this occurs, an Adequate
Intake (AI) value is determined. The Adequate Intake (AI) value is a recommended average daily
nutrient intake level based on observed or experimentally determined estimates of nutrient intake by
a group of healthy people. The Tolerable Upper Intake Level (UL) is the highest average daily
nutrient intake level likely to pose no risk of adverse health effects to almost all individuals in
particular life stage and gender group. The Estimated Energy Requirement (EER) is defined as
the average dietary energy intake that is predicted to maintain energy balance in a healthy individual.
This dietary intake is defined by a person’s age, gender, weight, height, and level of PA that is
consistent with good health. Carbohydrates, proteins, and many types of fats have an RDA. In
addition, the Acceptable Macronutrient Distribution Range (AMDR) identifies a range of
intake for the three energy nutrients that is both adequate and associated with a reduced risk of
chronic disease. The AMDR is expressed as a percentage of total energy (or total kcal). The AMDR also
has a lower and upper boundary.
How do nutrition professionals assess nutritional status?
Malnutrition refers to a state in which a person’s nutritional status is out of balance; the individual is
either getting too much or too little of a particular nutrient or energy over a significant period of time.
Nutrition professionals follow the four steps of the Nutrition Care Process, which include:
nutritional-status assessment, nutrition diagnosis, nutrition intervention, and nutrition monitoring
and evaluation.
There are five domains of Nutritional Status Assessment:
1. Food/Nutrition-Related History
These are all subjective; they rely on a person’s self-report.
a. Diet History
Typically conducted by a nutrition professional. Diet history information is
gathered using either an interview process or a questionnaire.
b. Twenty-Four-Hour Dietary Recall
Used to assess recent food intake. A trained nutrition professional interviews the
person and records his or her responses.
c. Food-Frequency Questionnaire
These questionnaires include lists of foods with questions regarding the number of
times these foods are eaten during the specified time period.
d. Diet Record
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