Discussion 5

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 (2^nd ed.). New York, NY:
       Oxford University Press.

Body Ecology Inc. (2008). The 6 benefits of monounstaturated fats (MUFAs). Retrieved

June 1, 2013, from http://bodyecology.com/articles/6_benefits_monosaturated_

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 (12^th ed).
       Belmont, CA: Cengage Learning.

Wildman, R. E. C. (2009). The nutritionist: Food, nutrition, and optimal health
       (2^nd Ed.). New York, NY: Routledge.