Samenvatting
Summary Understanding Nutrition
Summary of the necessary chapter for Open University. There is a very small part in Dutch.
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Samenvatting voeding en gezondheidAn overview of nutrition
Food choices based on:
Preferences for sweetness of sugar and savouriness of salt. High-fat also common preference. Genetics,
hormones and pregnancy may influence taste perceptions.
Habit
Ethnic heritage and regional cuisines; people tend to prefer foods they grew up eating
Social interaction
Availability, Convenience, and economy
Positive and negative associations
Emotions; food can influence brain’s chemistry and the mind’s response. Carbohydrates and alcohol, for
example, tend to calm, whereas proteins and caffeine are more likely to stimulate.
Values
Body weight and image
Nutrition and health benefits
- Functional foods: foods that provide health benefits beyond their nutrient contributions. Whole foods, as
natural and familiar as oatmeal or tomatoes, are the simplest functional foods. Sometimes also fortified
foods by adding nutrients or phytochemicals (nonnutrient compound of plant that have sometimes
biological activity) to provide health benefits
The ongoing growth, maintenance and repair of body tissues depend on
Energy: capacity to do work. Energy in foods in chemical energy. Body can convert this to mechanical, electrical
or heat energy.
Nutrients: chemical substances obtained from food and used in the body to provide energy, structural material,
and regulating agents to support growth, maintenance, and repair of tissues.
Body composition – mostly water (60%) and some fat (19-21% young men, 23-26% young women) with carbohydrate,
proteins vitamins, minerals, and other minor constituents making up the remainder.
Chemical composition of nutrients
- Minerals: simplest of nutrients. Each mineral is a chemical element; its atoms are alike. As a result, its
identity never changes.
- Water: next simplest nutrient, a compound made of two elements – hydrogen and oxygen.
Both water and minerals are inorganic – they do not contain carbon
- Carbohydrates, lipids, proteins, and vitamins are more complex. They all contain carbon organic
compounds.
Essential nutrients: nutrients that a person must obtain from food because body
cannot make them for itself in sufficient quality (also indispensable nutrients).
Energy-Yielding nutrients: carbohydrate, fat and protein; sometimes called
macronutrients, body needs them in relatively large amounts. Energy released from
energy-yielding nutrients can be measured in calories.
High energy density helps with weight gain¸ whereas low energy density helps with weight loss. Most foods contain
energy-yielding nutrients, as well as vitamins, minerals, water, and other substances. Exception to this rule is FE sugar
(only carbohydrates) and oil (pure fat).
Energy in the body: When the body uses carbohydrates, fat, or protein to fuel its activities, bonds between nutrient’s
atoms break and they release energy. Some is released as heat, but some is used to send electrical impulses through the
brain and nerves, to synthesize body compounds, and move muscles. If the body does not use these nutrients, it
converts them into storage.
In addition to providing energy, carbohydrates, fat, and protein provide raw materials for building body’s tissues.
Protein’s fuel source is relatively minor compared with both the other two energy-yielding nutrients.
,Vitamins: Facilitate the release of energy from energy-yielding nutrients and participate in numerous other activities in
the body. Function only when they are intact. Because they are complex organic molecules, they are vulnerable to
destruction by heat, light, and chemical agents.
Minerals: Structures bones and teeth. Also found in the fluids of the body, which influences fluid balance and
distribution. They do not yield energy! They are inorganic, therefore indestructible. They can, however, be bound by
substances that interfere with the body’s ability to absorb them. They can also be lost during food processing.
Water: Provides the environment in which nearly all the body’s activities are conducted.
Nutritional genomics: science of how nutrients affect the activities of genes and how genes affect the interactions
between diet and disease.
When doing research, researchers typically divide subjects into two groups, experimental group (receives vitamin
supplement) and control group (does not receive).
Randomization: subjects are chosen randomly from the same population. Helps to eliminate bias and ensure groups are
equal.
Blind experiment: subject does not know whether they are members of experimental group or the control group.
Double blind experiment: researchers also don’t know which subjects are in which group
As evidence accumulates, scientist begin to develop a theory that integrates the various findings and explains the
complex relationships.
Positive correlation: the more vitamin C, the more colds (both variables change into the same direction)
Negative correlation: the more vitamin C, the fewer colds (variables change into different directions)
Correlational evidence only proves that variables are associated, not that one is the cause of another. Therefore you
have to find evidence of the mechanism – explanation of how A might cause B.
Four categories of DRI (Dietary Reference Intakes)
Estimated average requirements (EAR): requirement for a nutrient. It is the average amount that appears
sufficient for half of the population.
Recommended dietary allowances (RDA): what intake to
recommend for everybody. Probably closest to everyone’s
need. Recommendations are set greater than EAR to meet
the needs of most healthy people. RDA are set near the top
end of the range of the population’s estimated
requirements.
Adequate Intakes (AI): for some nutrients there is
insufficient scientific evidence to determine EAR (needed to
set RDA). AI reflects the average amount of a nutrient that a group of healthy people consumes
Tolerable Upper Intake Level (UL): point beyond which a nutrient is likely to become toxic.
Energy recommendations
Estimated Energy Requirement: average dietary energy intake that will maintain energy balance in a person who
has a healthy body weight and level of physical activity. Any amount in excess of energy will result in weight
gain, therefore no upper level.
Acceptable Macronutrient Distribution Ranges (ADMR): composition of a diet that provides adequate energy
and nutrients and reduces risk of chronic diseases is:
- 45 to 65 percent kcal carbohydrate, 20 to 35 kcal from fat, 10 to 35 kcal from protein
Malnutrition: any condition caused by excess or deficient food energy or nutrient intake or by an imbalance of
nutrients.
Nutrition assessment:
Historical information: person’s history with respect to health status, socioeconomic status, drug use and diet.
Anthropometric measures: height and weight. However, provide little information about specific nutrients.
Physical examinations: visual inspection of the hair, eyes, skin, posture, tongue, and fingernails.
Laboratory tests
Primary deficiency: a nutrient deficiency caused by inadequate dietary intake of a nutrient. Secondary deficiency:
caused by something other than an inadequate intake such as a disease or drug interaction. Subclinical deficiency: in
the early stages, before the outward signs have appeared.
,Digestion, Absorption and Transport
Digestion is the body’s way of breaking down foods into nutrients in preparation for absorption. Challenges:
Food and liquid must go to the stomach. The throat must be arranged so that swallowing and breathing don’t
interfere.
Body needs a passageway that will allow food from the mouth to pass through the diaphragm to reach the
stomach below
Contents of digestive tract should be kept moving forward, slowly but steadily, at a pace that permits all
reaction to reach completion
Food must be lubricated with fluids. The amount of fluids
must be regulated to keep the intestinal contents at the
right consistency to move along smoothly.
For digestive enzymes to work, foods must be broken
down into small particles and suspended in enough liquid
so that every particle is accessible. Excreting all the water
along with solid residue would be wasteful and messy.
Some water must be withdrawn, leaving a solid waste
product that is easy to pass.
Digestive enzymes are designed to digest carbohydrates,
fat, and protein. Cells of the GI tract are also made of
carbohydrates, fat, and protein. These cells must be
protected against the powerful digestive juices that they
secrete.
Once wastewater has reached the end of the GI tract, it
must be excreted. Evacuation needs to occur periodically.
Gastrointestinal (GI) tract (maagdarmkanaal): flexible muscular tube that extends from mouth, through the
oesophagus, stomach, small intestines, large intestine, and rectum to the anus. Inner space of GI tract, lumen, is
continuous from one end to the other. Only when a nutrient or other substance finally penetrates the GI tract’s wall
does it enter the body proper; many materials pass through the GI tract without being digested or absorbed.
Mouth: During chewing, teeth crush large pieces of food into smaller ones, and fluids from foods, beverages and
salivary glands blend with these pieces to ease swallowing. Fluids also help dissolve the food so the tongue can taste it.
Taste buds detect one or a combination of the five basic taste sensations: sweet, sour, bitter, salty and umami. Aroma,
appearance, texture, and temperature also affect a food’s flavour. When food is swallowed, it passes through the
pharynx (keelholte), a short tube that is shared both by the digestive system and the respiratory system. To bypass the
entrance to the lungs, the epiglottis (strotklep) closes off the airway. After a mouthful of food has been chewed and
swallowed, it is called a bolus.
Esophagus (slokdarm) has a sphincter (sluitspier) at each end. During a swallow, the upper esophageal sphincter opens.
Bolus slides down the esophagus, which passes through a hole in the diaphragm to the stomach. The lower esophageal
sphincter at the entrance to the stomach closes behind the bolus so that it proceeds forward and doesn’t slip back into
the esophagus.
Stomach: retains the bolus for a while in its upper portion. Little by little, stomach transfers the food to its lower
portion, adds juices to it, and grinds it to a semiliquid mass called chyme (maagbrij). Stomach then, bit by bit, releases
the chyme through the pyloric sphincter, which opens into the small intestine and then closes behind the chyme.
Small intestine: chyme bypasses through the opening from the common bile duct, which is dripping fluids into the small
intestine from two organs outside the GI tract – gallbladder and pancreas. The chyme travels down the small intestine
through its three segments – duodenum, jejunum, and the ileum – almost 10 feet of tubing coiled within the abdomen.
Large intestine: the remaining contents arrive at another sphincter: the ileocecal valve, located at the beginnen of the
large intestine (colon) in the lower right side of the abdomen. Upon entering the colon, the contents pass another
opening. It would end up in the appendix¸ a blind sac about the size of your little finger. Normally, the contents bypass
this opening, however, and travel along the large intestine up the right side of the abdomen, across the front to the left
side, down to the lower left side, and finally below the other folds of the intestines to the back of the body, above the
rectum. As the intestinal contents pass through the rectum, the colon withdraws water, leaving semisolid waste. The
strong muscles of the rectum and anal canal hold back the waste until it its time to defecate. Than the rectal muscles
relax, and the two sphincters of the anus open to allow passage of the waste.
, Peristalsis: entire GI tract is ringed with circular muscles. Surrounding these rings of muscle are longitudinal muscles.
When the rings tighten and the long muscles relax, the tube is constricted. When the rings relax and the long muscles
tighten, the tube bulges peristalsis – occurs continuously and pushes the intestinal contents along.
Stomach action: has thickest walls and strongest muscles of GI tract. In addition to the circular and longitudinal muscles,
it also has a third layer of diagonal muscles that also alternately contract and relax.
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