Fats, Carbohydrates & Proteins:
Digestion, Absorption, & Benefits For The Body
We talk a lot about nutrition,
nutrient rich foods, and how important a nutritious diet really is, but you may
be wondering what exactly nutrients are, how our bodies utilize them, and what
role they play in our overall health.
This article will answer these basic questions, as well as clarify some
common misunderstandings with regard to fat and carbohydrates.
The Six Essential Nutrients:
A major element of following a
healthy diet involves monitoring and maintaining a steady intake of
nutrients. Thus, it is essential that we
understand what our foods are comprised of.
Before you get all skeptical about reading about components, hear me
out. It is really quite simple.
There are 6 basic types of nutrients in foods. According to Sizer and Whitney (2012), they
are:
1. water
2. fat
3. carbohydrates
4. protein
5. vitamins
6. and
minerals
Water is by far considered the most important nutrient for
the body (Wildman, 2009). Vitamins and
minerals are also absolutely essential in health because they help to maintain
the proper functioning of bodily systems (Wildman, 2009). But today, we are only going to discuss the
“energy-yielding nutrients,” the nutrients that provide our body with fuel for
life: fat, carbohydrates, and protein.
Fat:
The fatty acids in our diets often get a bad rap for their
ability to help us pack on the pounds when eaten in excess, but they are a
necessary part of a healthy diet. Fats
can be converted into energy for the body when needed, but their most important
role involves their storage in the body for future use (Brown, 2011). There are three major types of fats found in
our foods: saturated fats, trans fats and unsaturated fats (monounsaturated and
polyunsaturated) (Brown, 2011).
Cholesterol is also considered part of this fatty acid family. All fats can make you fat if you consume them
in excess, but different fats have different effects on the body and our
health. The difference in the types of
fats all boils down to their molecular level, and how much hydrogen they
contain. According to nutritionists, the
less hydrogen atoms a fatty acid has – the better. Saturated fats have higher amounts of
hydrogen atoms, as do trans fats – the man-made forms of fat. On the other hand, the unsaturated fats (MUFAs
and PUFAs for short) maintain much less hydrogen and are therefore better for
health. Saturated and trans fats
increase blood cholesterol levels in the body, which subsequently puts
individuals at higher risks of developing some serious chronic diseases like
cardiovascular disease, and can also lead to stroke or even an early death
(Brown, 2011). Unsaturated fats (when
consumed in adequate amounts) have the potential to reduce cholesterol, even
blood pressure, and promote overall heart health (Sizer & Whitney, 2012).
They are also associated with lower levels of fat in the body (Body Ecology,
2008).
Digestion of fats begins with the saliva, which contains an
enzyme called lipase. Because fats float
on the surface of water in the stomach, they are not digested in the
stomach. Instead, fats are only digested
in the small intestine, where are they dispersed with the help of a bile
produced by the liver, but housed by the gallbladder (Sizer & Whitney,
2012). The bile works to disperse the
fat into water where lipase enzymes produced by the pancreas are able to fully
break down fat molecules (Brown, 2011).
Nutrient absorption takes place in the small intestine along a cell wall
where broken down nutrients enter the blood stream (Brown, 2011). Thus, once fat is digested in the small
intestine it can be immediately absorbed by the body, or stored for future use
(Brown, 2011).
Carbohydrates:
The very “first link in the food chain that supports all
life on Earth” is the carbohydrate (Sizer & Whitney, 2012, p.107).
Composed of basic sugars, carbohydrates come
in multiple forms: monosaccharides, disaccharides and polysaccharides (Brown,
2011).
Simple sugars belong to the
monosaccharides group, while starch and fiber belong to the polysaccharides
group (Brown, 2011).
Their names reflect
how many sugar units are present in the carbohydrate molecules, but we won’t
delve too far into scientific terms here.
Carbohydrates are the single largest source of energy for the body
(Brown, 2011).
They supply us with the
fuel we need to perform just about any function.
They support our brains and nervous system,
and also are essential in the proper functioning of body tissues (Sizer &
Whitney, 2012).
Digestion of carbohydrates occurs differently depending on
whether the carbs are simple sugars, starch, or fiber. Digestion of carbohydrates in the form of
starch begins as soon as food enters the mouth and is mixed with an enzyme
found in saliva known as amylase (Brown, 2011).
Once passed through the stomach and into the small intestine, starch is
further digested by amylase produced by the pancreas, and is processed into a
simple sugar (glucose) for absorption by the body (Barasi, 2003). For complex sugar carbohydrates, the primary
process of digestion takes place in the small intestine where three enzymes –
sucrase, lactase, and maltase – are produced and work to break down the
polysaccharides (complex carbohydrates) into glucose (Barasi, 2003). Once the carbohydrates are broken down into
their most basic form, they are absorbed through the cell lining of the small
intestine and released into the blood.
If simple sugars (monosaccharides) are eaten, they are ready to be
absorbed into the blood and need no digestion because they are already at their
most basic state (Sizer & Whitney, 2012).
Carbohydrates in the form of fiber are not digestible by the body simply
because they cannot be broken down by any enzyme (Sizer & Whitney, 2012). Therefore, fiber passes through the digestive
tract and creates bulk in the feces (Brown, 2011).
Despite the inability for the body to use fiber
carbohydrates as energy, fiber presents a multitude of benefits for the body
and overall health. It has the ability
to reduce constipation and increase proper functioning of the bowels, improves
overall digestion, “lowers the risk of heart disease, obesity and diabetes” and
can promote a healthy weight (Brown, 2011, Section 12-11). Certain types of
fiber can also reduce overall food intake because of their ability to provide a
feeling of fullness when eaten. Fiber
also slows the absorption of simple sugars, thus reducing blood sugar spikes or
drops. Finally, fiber has the special
ability to prevent cholesterol and fat from being absorbed into the blood
stream, and generally reduce blood pressure (Brown, 2011). These functions of fiber are why it is
believed to lower the risk of heart disease.
Proteins:
The third energy-yielding nutrient is protein.
Proteins serve as the body’s buildings blocks and
are themselves comprised of a variety of components known as amino acids
(Wildman, 2009). Proteins are essential
nutrients for the body, helping to build and maintain bones, tissues and
muscles, regulate hormones, and carry substances through the body (Wildman,
2009).
Proteins are so vital to health
simply because “amino acids must be continuously available to build the
proteins of new tissue” (Sizer & Whitney, 2012, p. 199).
When a food containing protein is eaten, digestion begins
only at the stomach, where pepsin, an enzyme produced by the stomach, begins
break down proteins into simple amino acids known as polypeptides (Brown,
2011). After the stomach has done its
work, the amino acids are sent to the small intestine where trypsin, an enzyme
produced by the pancreas, works to break these acids down further (Brown, 2011). Like in all other instances of nutrients, the
cells in the small intestine absorb the basic amino acids and send them out
into the bloodstream where they used by the body (Sizer & Whitney).
Fats, carbohydrates and proteins are energy-yielding
essential nutrients needed for health.
Although the topic can be overly scientific at times, it is important to
develop a basic understanding on the relationship between nutrients, the body,
and health. Using this information in
application to your diet cannot only help you improve your health, it can help
you live better, and perhaps longer.
References
Barasi, M. E. (2003). Human
nutrition: A health perspective (2nd ed.). New York, NY:
Oxford University
Press.
Body Ecology Inc. (2008). The 6 benefits of monounstaturated fats (MUFAs). Retrieved
fats.php#.Uaya0-tMaIk
Brown, J. E. (2011).
Nutrition
now (6
th ed.). Belmont, CA: Wadsworth Cengage Learning.
Sizer, F. S., & Whitney, E. N. (2012). Nutrition: Concepts and controversies
(12th ed).
Belmont, CA: Cengage Learning.
Wildman, R. E. C. (2009). The nutritionist: Food, nutrition, and optimal health
(2nd
Ed.). New York, NY: Routledge.
