Fats, proteins and carbohydrates in the body

How are fats, proteins, and carbs digested and absorbed in the body? What are the benefits from a dietary perspective? What are the good fats, bad fats, etc.? Why is fiber so beneficial?

            Fats, proteins and carbs (three of the six essential nutrients in a balanced diet) serve many functions in the body. Our bodies need a balance of water, fats, protein, carbohydrates, minerals and vitamins to survive and properly functions. If even one of these nutrients become deficient in the diet the body would not be able to properly function, perform maintenance tasks, and would eventually shut down do to lacking nutrients. Carbohydrates offer much needed energy; fat offers concentrated energy; and protein, if necessary, can offer energy plus nitrogen” (Sizer, 2011).

Carbohydrates are “compounds composed of single or multiple sugars” (Sizer, 2011). Sugars, starches and fiber are all included the carbohydrate family, and all play an important role in body. Carbs provide only 4 calories per gram, and supply energy for many physical activities and vital functions. “Six sugar molecules are important in nutrition” (Sizer, 2011), and include monosaccharides (single sugars) and disaccharides (double sugars). Glucose, a the most important monosaccharide found in the human body, and also is found in both plant and animal tissues. It is an important supply of fuel and energy for most of the body’s functions. Glucose particularly aids nerve cells, and more specifically is necessary for brain health (Sizer, 2011). “Just as plants store glucose in long chains of starch, animals store glucose in long chains of glycogen” (Sizer, 2011). Glycogen is complex polysaccharide that is stored in living human and animal muscle tissues and in the liver (as the storage form of glucose). When the body runs out of actively circulating glucose in the body, it taps into its stored glycogen supply and through a complex process transforms it into usable glucose. When considering what carbs to eat, choose complex ones. Complex carbohydrates (also known as polysaccharides) are long chains of sugar units built to form either starch or fiber. Simple carbohydrates, however, are single sugar units, which is a basic molecule made up of six carbon atoms, along with oxygen and hydrogen atoms. Fiber-rich and complex carbohydrate packed foods are the more healthy options for adding glucose to the diet. These foods include whole grains, a variety of vegetables, fruits and legumes. They are typically high in minerals, vitamins, phytochemicals, and have little fat or are naturally fat free. Now, fiber, the indigestible part of plant foods, does not provide any energy, but it does provide great health benefits to the body. Fiber comes as both water-soluble and insoluble polysaccharides, and include “cellulose, hemicelluloses, pectins, gums, mucilages, and the nonpolysaccharide lignin” (Sizer, 2011). Soluble fibers, which can be dissolved in water, create a gummy or jelly type substance, and aid in the lowering blood cholesterol and help control blood glucose levels. Insoluble fibers, however, cannot be broken down and retain their tough structure, which aids in adding bulk to feces for easy elimination. Both types of fiber aid in a healthy digestive track. Digestible forms of carbs need to be broken down into the usable form of glucose, and this process begins in the mouth with the mixing of saliva. Depending on its digestible structure, starches tend to take the longest amount of time to be digested which lends to the slow release of sugars into the body. Refined carbs, however, tend to break down easily, dumping its sugars in the body quickly, which can spike blood glucose levels rapidly. This is why complex carbs are suggested to be consumed, instead of simple carbs.  But, both have their place in a complete diet. In addition complex carbs pack more fiber, especially viscous fibers, which “may lower blood cholesterol by binding with cholesterol containing compounds in bile” (Sizer, 2011).

 

“From the moment they enter the body, lipids affect the body’s functioning and condition” (Sizer, 2011). Fats begin to broken down in the stomach, where is separated from watery components in the food. Upon reaching the intestines the fat droplets are held together via bile, an emulsifier solution containing cholesterol compound which aids in the fat droplets digestion. “Once the intestine’s contents are emulsified, fat-splitting enzymes act on triglycerides to split fatty acids from their glycerol backbones” (Sizer, 2011). Fats serves many purposes, including padding for the more delicate features of the body, such as organs. It also surrounds cells for protection and structure. Some nutrients, such as in fat soluble vitamins A, D, E, and K, cannot be processed without fat. In addition, fat also aids in the absorption of various phytochemicals. Fats exist as triglycerides (contains fatty acids), phospholipids (similar to triglycerides) and sterols (best known as cholesterol). About 95% of fats found in foods and in the human body are fatty acids, and is made up of one unit of glycerol and three units of fatty acids. Phospholipids, found in cell membranes, “has a phosphorus-containing acid in place of one of the fatty acids” (Sizer, 2011), which makes it different from a triglyceride. Sterols have multiple functions including its role as part of the bile solution, vitamin D absorption, the function of sex hormone, and has a role in other important compounds. Plant sterols play an important role in inhibit cholesterol from being absorbed into the body (Sizer, 2011). Good fats include healthy mono and polyunsaturated fats, and bad fats include unhealthy saturated and synthetic trans fats. These fats and excessive amounts of cholesterol raise the risks of various diseases, and prevent the body from optimal functioning. They can increase the chances of obesity, certain cancers, clogged arteries, and heart disease. Heart healthy fats should be chosen instead, and adequate amounts of carbs must be consumed to help process fat. But, regardless of what type of fat it is, all fats, or lipids, contain the highest source of energy among the essential nutrients, packing 9 calories per gram. That being said “gram for gram, fats provide more than twice the energy of carbohydrates, making fat an efficient storage form of energy” (Sizer, 2011).

Protein is a vital nutrient that is important for the repair, regeneration and growth of various structures and tissues in the body. It is also important to aid in physical exertion and the maintenance of muscles after a physical activity takes place. Proteins can be broken down, or denatured, via heat, acids, bases, alcohol or by the salts in heavy metals. “Digestion of protein involves denaturation by stomach acid, then enzymatic digestion in the stomach and small intestine to amino acids, dipeptides, and tripeptides” (Sizer, 2011). The digestion of proteins begins in the stomach where a strong acids begins to break the proteins down and uncoils the molecular stands into more usable forms for the body. Every different type of protein performs a unique task once broken down into its building blocks. The building blocks of protein are amino acids, and there are over 20 different amino acid units. “The body need dietary amino acids to grow new cells and to replace worn-out ones” (Sizer, 2011). Essential amino acids are elements that the body does not or cannot make sufficient amounts of, but are vital for certain proteins to be synthesized. Dietary amino acids are crucial in the creation of proteins, and protein is crucial for muscle repair and growth, organ maintenance, injury repair, and blood cell replenishment. It also acts as a glue between cells (as collagen), helps to regulate blood glucose (as insulin), and works with other red blood cells to carry oxygen throughout the body (as hemoglobin). In addition, protein also helps to maintain electrolyte and fluid balance within the body. The easily manipulated structure of proteins allows it to perform a variety of important functions throughout the body. We need protein on a daily basis as cells are overturned. “The DRI recommended intake for adults is 0.8 gram of protein per kilogram of body weight” (Sizer, 2011), but physical activity also needs to be factored in as well. According to the DRI I require about 46 grams of protein, which I achieve on a daily basis through eating a variety of proteins. Protein only packs 4 calories per gram consumed. “Proteins provide structure and movement; serve as enzymes, hormones, and antibodies; provide molecular transport” (Sizer, 2011).

Long story short, we need to eat a balanced diet, and a variety of whole foods, in which work together to provide our bodies with the tools to achieve and maintain a healthy life.

Resources

Sizer, F., & Whitney, E. (2011). Nutrition concepts and controversies (12^th ed.). Belmont, CA:Wadsworth learning.