Nutrient Sources and
Their Absorption.
Every living thing needs energy via nutrients to survive,
even the most seemingly inanimate organisms like plant require the nutrient
they get from sunlight and water to survive and even thrive. Humans being, the
most advanced of living organisms are no different. In fact, the proper
nourishment of humans is a bit more sophisticated than just consuming any food.
Individuals require all necessary nutrients, the Macros or energy yielding. In
addition the micronutrients vitamins and minerals are just as vital for their
supporting and protective properties
As previously implied there are six classes of
nutrients that broken into energy yielding (Macronutrients), and supporting
(micronutrients), these nutrients are also considered essential nutrients
because they cannot be produced by the body (Anspaugh et al), and are thus
required to be consumed through food. The four Macronutrients or energy
yielding nutrients are indirectly derived from the sun, either through the
consumption of plant based foods or, plant eating animal foods, they are
“organic; that is, the nutrients contain the element carbon derived from living
things” (Sizer & Whitney 2013 p 7). The macronutrients are:
Carbohydrates: which are made up of sugar units
(saccharides) and are broken down in the body as such (Richards 2009).
Carbohydrates can be simple (Simple sugars, quickly digested) or complex
(starches and fibers, take more time to be broken down), however whichever from
it comes in is broken down to its simplest form, glucose and used as energy in
the body. Most if not all carbohydrates are plant based and the main source of
energy yielding nutrients. Some foods that are sources of carbohydrates are
grains, vegetables, fruits and legumes (Anspaugh et al 2011).
The next energy yielding macronutrient is Protein,
which is in addition to carbon also contains hydrogen and nitrogen (Anspaugh et
al 2011). Protein aids cell growth, tissue repair, as well as maintains the
functionality and regulation of cells, organs, hair, skin and nails. The
building blocks of proteins are amino acids, of which there are approximately
20. 11 are non-essential meaning they can be produced by the body; the
remaining 9 however must be acquired from food. Even though protein is an
energy-yielding nutrient, it would be ineffective as the only source of energy
as it does not yield enough, it must be coupled with other nutrients. Foods
that are a source of protein are meat, fish, milk, eggs, pulses, legumes, nuts
and seeds among others.
Another energy yielding macronutrient is Fat, which are
oils, sterols and waxes. They not water soluble (water and oil don’t mix), and
are high in calories, which is why a small amount of fat is recommended in
daily diet. Fat is a however an essential component of all cells, and aids in
the synthesis and repair of vital cell transport and absorption of fat-soluble
vitamins. Fats that remain liquid at room temperature like olive oil, rapeseed
oil (canola), grape seed oil; sunflower oils etc. are generally better than
those that solidify like butter, margarine and coconut. Fat consumption should
be kept to a minimum, especially if carbohydrate consumption high.
While all nutrients are important one of the most
important is water, which performs many functions. The human body can survive
up to 3 weeks without food, however it can only survive about 3 days without
water, that how important water is to the body. Water is essential for the body
to function properly, it makes up about two thirds of the human body an every
chemical reaction, lubrication, nutrient transportation and removal of toxins
and waste requires water (Richards 2009). It is recommended that 6-8 glasses of
water be drunk each day, and many fruits and vegetables also contain water.
Micronutrients like vitamins, minerals and trace
elements are also essential for proper bodily function, however they are only
needed in small quantities (Richards 2009).
Vitamins are organic, containing carbon and can be
found in plant or animal based foods, as prior mentioned they are only needed
in small amounts for proper function of the body (Anspaugh et al 2011).
Vitamins are essential nutrients because the body cannot produce them and as
such have to be consumed through daily diet, “Unlike carbohydrates, fats, and
proteins, vitamins yield no energy. Instead, some serve as catalysts that
enable energy nutrients to be digested, absorbed, and metabolized (Anspaugh et
al 2011. p191). Some vitamins interact with minerals to aid their absorption,
while some act as antioxidants to neutralize free radicals and toxins in the
body (Anspaugh et al 2011).
Minerals are also simple, but important nutrients,
and like vitamins are only needed in minute quantities. The compositions of
mineral are inorganic, and they are found in rocks or soil. However they can
also be consumed through plants and animals, as plants can absorb them from the
ground and plant-eating animals can ingest and digest them (Richards 2009).
Minerals like vitamins are not energy yielding, and “As inorganic compounds,
they lack the complexity of vitamins, but they fulfill a variety of functions.
For example, sodium and potassium affect shifts in body fluids, calcium and
phosphorus contribute to the body’s structure, iron is the core of hemoglobin
(an oxygen-carrying compound in the blood), and iodine facilitates production
of thyroxin” (a hormone that influences metabolic rate) (Anspaugh et al P197).
Here is a video on how it works.
According to the required text, Nutrition: Concepts and Controversies when the body needs food, the
brain sends a signal to the consciousness which illicit the feeling of hunger
(Sizer & Whitney 2013), this is but a precursor to the digestive process.
When food id introduced in to the body, “The digestive system transports
nutrients, water and electrolytes from food into the body’s inner environment…
Food provides a source of energy for the production of adenosine triphosphate
(ATP) by cells so that the functions of active transport, contraction,
synthesis and secretion, which are energy-dependent activities, can be carried
out (Sherwood 2013). Food is also required so that body tissues can be repaired
and renewed and for this to occur, food needs to be processed into a form that
the body can use readily” (Hendry et al 2014, par 17).
In other words the purpose of the digestive system is
to break down food to its simplest form, so that it can be absorbed and
transported to all parts of the body that need the necessary nutrient. While
some nutrients can be produced in the body, most need to be ingested in the
form of food. And those produced by the body, require energy for the production
process. Some evolutionary scientists might imply that the digestive system is
a sophisticated piece of ‘equipment’, which by its evolution provides new and more
effective opportunities for nutrition (Broderick 2015).
The digestive system consists from an array of organs
beginning from the mouth and ending at the anus, and is mostly run by the
autonomic nervous system (Johnstone et al 2014). The organs, which make up the
digestive system include the : Mouth, Pharynx, Esophagus, Stomach, Small
intestine, Large intestine, Rectum and anal canal. As food passes through the
digestive tract, each organ performs a function to aid digestion and the
absorption of nutrients. Other accessory organs like the Teeth, Tongue, major
pairs of salivary glands, Liver, Pancreas, Gall bladder also assist the
digestive system in this of consuming and digesting food, absorbing nutrients
and expelling waste from the body. The digestive system works in two ways to
perform these functions, mechanical and chemical.
The mechanical aspect of digestion food being broken
down into its smaller particles, mixed up with digestive juices as it moves
along the gastrointestinal tract, and the rest removed from the body as feces
(Hendry et al 2014). In greater detail, mechanical digestion begins in the
mouth, where pieces of food are torn apart and mixed with saliva. At this stage
chewing is very important, because it allows enzymes and digestive acids to
better break down food. Saliva also coats and moistens the food, making it
easier to pass down the esophagus (Sizer & Whitney 2013). The masticated
food, known as bolus is then transported through the esophagus to the stomach,
where it is held and ground into a fine paste to aid the remainder of the
digestive process. Water and digestive juices is also added to the finely
ground up food as well, now forming chyme. The chime through the muscular
pyloric valve, is forcefully squirted into the small intestine a little at a
time. This process is completed a few hours after the meal is consumed. Most of
digestion and the absorption of nutrients occur in the small intestine, which
is about six meters long. The small intestine is designed to maximize the absorption
of nutrients with its maximal surface area consisting of villi and microvilli
(Johnstone et al 2014). The remainder, which is not able to be digested is then
moved to the large intestine. Regardless of its name, the large intestine or
colon is only about 1.5m long and
continues from the end of the ileum, the latter part of the small intestine to
the anus (Johnstone et al 2014). Even though the main function of the large
intestine is to expel waste from the body, there is still some absorption of water
and minerals prior donated by former digestive organs leaving behind undigested
materials as fecal matter excreted by the body as waste (Sizer & Whitney
2013).
The chemical aspect of digestion “occurs when food is
broken down into absorbable units so that they can pass through the intestinal
mucosa into the circulatory system (Hendry et al 2014, par 17). In chemical
digestion, food is hydrolyzed using enzymes from different organs. This process
also begins in the mouth, as an enzyme in saliva begins breaking down starch
from carbohydrates and some fat, particularly milk fat (Sizer & Whitney
2013). The digestion of protein does not begin until it reaches the stomach,
here the release of gastric juices; which is a mixture of water, enzymes and
hydrochloric acid activates a protein-digesting enzyme to begin the digestion
of protein. In the small intestine, the work that was begun in the mouth and
stomach gets underway as the gallbladder and pancreas secrete bile and
pancreatic juices in just the right amounts to support the digestive enzymes in
the small intestine. Sugar and starch are broken down to monosaccharaides and
absorbed. Fibers are not digested, however they bind to fat and some minerals
on their way to the large intestine. Fats are broken down to fatty acids by the
bile from the liver by way of the gallbladder and are absorbed as such.
Proteins are broken down into amino acids by enzymes in the small intestine and
pancreas before it is absorbed. The prior mentioned fiber is relieved of more
water and minerals before it excreted as part of the feces (Sizer & Whitney
2013).
Without a doubt the digestive tract/system is a very
important part of every human body, however not much consideration is given to
it until there is discomfort and sometime even that is ignored. According to
the required text in A Letter from your
Digestive Tract, many food choices and the way they are consumed contribute
greatly to discomforts and digestive disorders. Consuming foods to fast can
cause hiccups, while consuming too much of new foods can lead to excessive
flatulence, which could be serious. In addition, overeating causes the acidic
juices to rise back up the esophagus causing heartburn. However some more
serious conditions, like hernia, and ulcers could be the cause and should be
checked out by a physician instead of self-medicating, constipation and
diarrheas are also signs that the digestive system is afflicted. To avoid these
conditions among others, healthy food choices should be consumed regularly. New
foods should be introduced slowly, a little at a time, and Foods should be
eaten in a relaxed manner (Sizer & Whitney 2013). The digestive system
works for the human body, and ensures that food taken in is broken down
(digested), and absorbed to produce energy for every bodily function; the most
humans can do is help it along by feeding the body right.
References:
Anspaugh, D. J., Hamrik, M. H., & Rosato, F. D. (2011).
Wellness concepts and
applications. (8th
ed.). New York: NY, McGraw-Hill Higher Education
Broderick, N. A. (2015). A common origin for immunity and
digestion. Frontiers In
Immunology, 61-3.
Hendry, C., Farley, A., McLafferty, E., & Johnstone,
C. (2014). The digestive system: part
2.Nursing Standard, 28(25), 37-44.
Johnstone, C., Hendry, C.,
Farley, A., & McLafferty, E. (2014). The digestive system: part
1.Nursing Standard, 28(24), 37-45.
Richards, S. (2009). The building blocks of a healthy
diet. Practice Nurse, 38(3), 12-17.
Retrieved from EBSCOhost.
Richards, S. (2009). The building blocks of a healthy
diet Part 2. Practice Nurse, 38(4), 29-33. Retrieved from EBSCOhost
Sizer, F. & Whitney, E. (2013). Nutrition:
Concepts and Controversies (13th ed.). Mason, OH: Cengage Learning.
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