What should I know about Fats, Proteins, Carbohydrates and Fiber?

In order for the human body to grow, survive and maintain health, a person must take in nourishment and energy from the foods that they eat.  When we choose something to eat, that food may contain some of or a combination of the macro nutrients; fat, protein, carbohydrates and fiber.  For example, an avocado contains all of these important macro nutrients fat, protein, carbohydrates and fiber (Vukovic, 2007).  Once we eat an avocado, how does our body receive and utilizes these macro nutrients and why are they beneficial to our body?  In order to better understand this concept, I will explore how the human body digests and absorbs the carbohydrates, protein, fiber and fat that is found in the foods that we may eat as well as discuss the benefits they offer to our body.

Carbohydrates

The glucose that is found in carbohydrates is a vital fuel for most body functions.  Carbohydrates also feed the brain and nervous system, keep the digestive system fit, and help keep the body lean (within calorie limits) Foods rich in carbohydrates include bread, potatoes, peas and beans, rice, pasta, fruits and vegetables.  Many of these foods contain both starch and fiber.   Your body cannot readily use the carbohydrates in the avocado and other forms of carbohydrates, therefore the various body systems must make the glucose from the carbohydrates available to the cells.  This is not done all at once, but at a steady rate throughout the day.  Digestions of starches and trace fats (especially milk fats) begin in the mouth where enzymes in the saliva breaks them down.  Then, while in the stomach, salivary enzymes are neutralized by stomach acids.  Next,  starches are delivered to the small intestines, where another starch splitting enzyme is delivered by the pancreas and lining of the small intestines which break them down even further so that they may be absorbed into the blood.  Glucose from the starches is then carried through the bloodstream to the liver, where it is stored or used to provide energy for the work of the body ( Sizer & Whitney, 2011 & "Your digestive", 2008).  Sucrose (table sugar) from carbohydrates are also digested by enzymes in the lining of the small intestines into glucose and fructose, which are then absorbed through the intestine into the blood.  Milk, has another type of sugar, lactose, when is also changed into absorbable molecules by another enzyme in the lining of the intestines ("Your digestive", 2008).


Fiber

Many carbohydrate-rich foods offer the additional benefit of fiber.  Fiber can be found in complex-carbohydrates such as whole grains, vegetables, legumes and fruits.  Fiber is beneficial because it helps maintain digestive tract health, help normalize blood cholesterol and blood glucose, maintain healthy body weight, and may also defend against cancers of the colon and rectum.  Fiber is mainly indigestible.  However, some fiber binds to cholesterol and minerals in the small intestines, while others are digested by bacteria in the large intestines or excreted with the feces (Sizer & Whitney, 2011 & "Your digestive", 2008). 

Proteins

Protein is found in every cell in the human body and is a major part of organs, muscles, skin, and glands. In addition, proteins provide energy and help the body repair cells and make new ones and are also essential for growth and development during childhood, adolescence, and pregnancy ("Protein", 2011). Protein is found in meats, milk, fish, soy, eggs, beans, legumes, and nut butters. The proteins in foods must be first digested by enzymes so they can be used to build and repair body tissue. This process begins in the stomach where enzymes in the juices start the digestion process and then the lining of the intestines complete the breakdown of protein molecules into small molecules called amino acids. These amino acids are then absorbed through the small intestine into the blood so they can be carried to all the parts of the body ("Your digestive", 2008).

Fats

Fat molecules are a rich source of energy for the body. Digestion of fat molecules start in the stomach where fats are separated from other rood components. Then, once they reach the small intestines the "digestive system mixes fats with bile- containing digestive juices to emulsify the fats; then, fat-digesting enzymes can break fats down" allowing the intestinal cells to absorb them. (Sizer & Whitney, 2011, p. 157). 

With all the information in the media about "good fats" and "bad fats" it could be difficult to decipher which fats your body needs and which ones it can do without.  There are four different types of fat; saturated fats, trans fat, monounsaturated fats, and polyunsaturated fats.  All of these fats are identical from a caloric point of view (1g fat = 9 calories), but all fats are definitely not identical when it comes to health (Sizer & Whitney, 2011).  For example-

Saturated Fat are considered "bad fats" and are solid at room temperature.  They can be found in butter, cheese, coconut oil, beef fat, palm oil, pork fat and chicken fat.  Saturated fats are known to elevate blood cholesterol and contribute to blood clotting linked to heart attacks (Sizer & Whitney, 2011).

Trans Fats are also known as "bad fats" and only occur in nature in small amounts (dairy products).  This type of fat is usually found in commercially fried foods such as donuts and chicken, baked goods, chips, cookies, crackers, bread and stick margarine.  Consuming foods that contain trans fat increase a person's risk to the heart and arteries by raising the "bad" LDL cholesterol and lowering the "good" HDL cholesterol.  Trans fats may also increase tissue inflammation, which is know to contribute to the development of heart disease.  "The Dietary Guidelines 2005 therefore suggest that people keep trans fat intake as low as possible" (Sizer & Whitney, 2011, p. 157).

Monounsaturated and polyunsaturated fats are considered the "good fats" and can be found in most vegetable and fish oils.  In addition to containing polyunsaturated fats, some vegetable oils, olive oil, and canola oils are rich in monounsaturated fats as well.  Monounsaturated fats can also be found in avocados and nuts.  Omega-3 polyunsaturated fatty acids are considered to be essential to the human body and are likely to lower blood pressure, prevent blood clots from forming, and protect against irregular heartbeats.  In addition, there is some evidence that Omega-3 fatty acids may also reduce the instances of inflammation which is linked with heart disease (Sizer & Whitney, 2011). 

Throughout our life time, we are faced with the task of choosing what to eat.  Knowing which foods benifit our body and which ones don't may help making those choices a little easier.  Therefore, allowing us to enjoy the taste of our food and the company in which we eat it with. 

References

Sizer, F. & Whitney, E. (2011). Nutrition Concepts and Controversies. Belmont, CA: Wadsworth

Vukovic, L. (2007). Inside & out. The beautiful side of avocados. Better Nutrition, 69(9), 44-45. Retrieved from http://web.ebscohost.com

Your digestive system and how it works. (2008). Retrieved from http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/