Digestion, Absorption, and Metabolism of The Macronutrients - Part IV of Ashford University Assignment

The following information comes from book -  Nutrition: Concepts and Controversies (14^th ed) by Sizer, & Whitney chapter 3.

When it comes to macronutrients (carbohydrates, protein, and fat) each one is digested, absorbed, and metabolized differently, which will be discussed in this blog post.

Carbohydrates are needed in order to supply ones body with energy, supply nutrients to ones brain and nervous system, and to keep ones digestive system healthy.  Carbohydrates enter the body through all sorts of different foods such as whole grains, fruits, beans, milk, and vegetables.  There are good carbohydrates and bad however, today we are simply going to discuss how carbohydrates are digested, absorbed, and metabolized.  Carbohydrates start to breaks down the minute one takes a bit of food to which the saliva within ones mouth releases enzymes needed to start the digestion process breaking down the starches.   Lets take an apple, as you start to chew the apple the saliva you create releases enzymes that will be with the apple as it makes its way to the stomach.  Not only that but the saliva coats the pieces of apple, making it easier to swallow.  Once in the stomach the food is squeezed and mashed into a fine paste where the stomach and intestines add water so that the paste (chyme) starts to turn more fluid like as it moves and mixes with the digestive chemicals/enzymes.  During this process the starches are partly split and if the apple was a piece of meat the proteins would have then been uncoiled with the fat being separated.  From here the chyme is squirted, a little at a time, into the small intestine and pushed into the large intestine by this time digestion is nearly finished.  The small intestine is where the final digestion process happens and where the absorption of nutrients and minerals happen before excreting the remainder through the large intestine. 

Much like carbohydrates the digestion of fats also starts with the enzymes of the mouth while the digestion of proteins begins in the stomach, which is its main function.  One of the main difference between the digestions of fat and that of carbohydrates and protein is that fat sits on top of the stomach fluid, is not digested there, and it is the last to leave the stomach.  Fat is mostly digested and absorbed in the body’s small intestine and with the remainder exiting the body along with the other waste.  Like fat and carbohydrates the digestion of proteins also begins in the mouth and like carbohydrates the digestion processes continues in the stomach until nearly all digestion is finished and absorbed in the colon.  Within 24 to 48 hours of eating a healthy body will digest and absorbs about 90 percent of the carbohydrates, fat, and protein in ones meal. 

When it comes to the absorption and transportation of nutrients it begins after the digestive system has broken down the food into its nutrient components.  In order for the molecule of nutrients to be absorbed into the body it must first attach itself to one of the cells lining the intestinal wall.  From there the cells absorb the nutrients and deposits the water-soluble nutrients/compounds into the blood while depositing the fat-soluble ones in the lymph vessels.  At this point the nutrients are then transported elsewhere for example, the lymph vessels transport the fat-soluble vitamins near the heart with the water-soluble ones being transported through the blood vessels to the liver.  From there the vitamins and minerals are then transported wherever they are needed. 
Carbohydrates, fat, and proteins are made up of amino acids which are the three main sources of energy that the body needs and are stored throughout the body making up ones metabolism (Frayn, 2010, para. 1).

References

Frayn, K. (2010). Nutrition: Macronutrient metabolism. Oxford. Oxford University Press. doi:10.1093/med/9780199204854.003.1101_updat_002
Sizer, F.,  & Whitney, E. (2017). Nutrition: Concepts and controversies. Cengage Learning: OH. Retrieved from VitalSource Bookshelf