Adequate protein consumption is important for optimal health and having a positive nitrogen balance and amino acid profile aids in muscle gain and maintenance at any age. Many professionals recommend one gram of protein per kilogram of lean body mass desired. The purpose of this document is not to investigate protein needs for a certain desired body composition goal, but to discuss the functions of protein within the body and various sources including benefits and drawbacks of each category of protein source.

Protein source selection consists of more than just reading a food label. The other factors to be considered are quality, digestion, absorption, and utilization. Some proteins may be much easier to digest than others and there is much variability in this regard. Lactose intolerance being one simple example. Absorption is also an important variable to be considered. The absorption of amino acids through the intestinal wall allows these potential building blocks the opportunity to be utilized. The ability of protein or amino acids to build tissues of many forms becomes one of the most crucial factors. The ability to utilize the different protein sources discussed will be a reoccurring theme throughout this document.

Proteins provide many vital functions within the body. Although I am not a proponent of a no carbohydrate diet, it has been mentioned by some that protein and fat are essential while carbohydrates are not. The reasoning behind this statement is that fat and protein can be converted to glucose for energy. Cell membranes are composed of a phospholipid bilayer and are very simply expressed as fat. Proteins are building blocks for tissue and provide many structural components of cells. Protein is also a part of hemoglobin which is the oxygen carrying component of red blood cells. Proteins are present in and constitute many hormones. All enzymes are proteins, but not all proteins are enzymes is how the saying goes. Enzymes catalyze many chemical reactions throughout the body. Protein also functions as albumins and globulins. Albumins function to provide osmotic pull to maintain fluid within blood vessels preventing edema. Globulins are carriers of minerals, enzymes, and hormones. Proteins are chains of amino acids connected by peptide bonds. For proteins to be absorbed and utilized, the digestive system and enzymes must recognize peptide bonds to create the proper environment. For this reason, free form amino acid products rarely provide much benefit. There are eleven non-essential amino acids meaning that they can be synthesized by the body if needed. There are also nine essential amino acids meaning that they cannot be synthesized and therefore must be consumed. A complete protein is one that contains all essential amino acids. Excess protein can be converted to glucose, and this happens on a regular basis, but this is not the reason protein is essential. Animal protein is closer to humans because we are animals making it easier to utilize than other protein sources. Animal protein has a utilization percentage of thirty percent with seventy percent converted to glucose. The utilization is much higher than plant-based protein which has a utilization of seventeen percent with eighty-three percent converted to glucose.

There are diverse sources of protein with a variety of benefits. Soy is a protein that is a staple of a vegetarian diet. There are various products that contain soy. Soy milk is often used as a protein source for many vegetarian nutrition programs. Soy milk is seventeen percent of utilization. Soy milk is often loaded with sugar. It is a genetically modified organism (GMO) food. This milk is often hard to digest and a common source of allergens. It also contains phytoestrogens which may cause hormone imbalances in both directions. Other soy products such as tofu and tempeh are better because they are fermented and contain bacteria that aids in digestion.

Beans and legumes are considered a good protein source. They have the same limitations as soy products. They are plant based, so they have the same utilization percentages, are hard to digest, and high in carbohydrates.

Egg whites are thought to be one of the best protein sources available. The problem becomes that they are incomplete without the yolk. This is the worst of the animal sources with the yolk discarded. Egg white has a utilization percentage of seventeen and is a common allergen.

Nuts and seeds possess the same utilization percentages as other plant-based proteins at seventeen with eight-three converted to glucose. Most contain healthy fats and are high in fiber. Pecans, walnuts, and macadamia nuts have extremely healthy fat profiles. Seeds such as pumpkin, chia, and flax are high in fiber. All these nuts and seeds have an anti-inflammatory effect.

Pork, turkey, and chicken are obviously good protein sources. They are animal sources which are thirty percent utilized with seventy converted to glucose. The most key factor with these meats is the quality. If these animals are well fed and lean healthy animals, it makes a considerable difference. Toxicity of these animal tissues are stored primarily in the fat. For this reason, the leaner cuts of these meats are healthier and better utilized.

Dairy products can be a useful source of protein. Milk is obviously an animal source with the same percentage of utilization. The best milk is grass fed or organic with grass fed preferred over organic. Some people have allergies to milk or suffer from lactose intolerance. Fermented milk products such as yogurt or sour cream are often better tolerated. Although whey protein comes from milk, it is inferior with the same utilization percentages as plant-based proteins. These protein powders do not provide an advantageous alternative. Cheese is another form of dairy product with the same utilization percentages. As with milk, grass fed or organic have fewer allergies.

Red meat such as beef and lamb are an excellent source of protein. Red meat is high in iron making it beneficial for red blood cell production. They are animal sources having the same utilization percentages. Again, grass fed or organic cuts of meat are better.

Fish that are caught wild are excellent sources of protein with the same animal utilization percentages. Fish is usually easily digested and contains beneficial polyunsaturated fatty acids. These fatty acids include eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA has beneficial to developing fetuses and combating various conditions including heart disease, diabetes, Alzheimer’s disease, and obesity. DHA is beneficial to cell membranes. Many types of fish have these, but salmon, mackerel, and sardines are particularly rich in these valuable fatty acids. Most fish are low in fat, but those with a higher fat content contain healthy fats.

The protein source that contains the highest percentage of utilization is whole eggs. Eating the entire egg including the yolk provides a complete protein with a utilization percentage of forty-eight. This is a dramatic difference compared to other animal sources. Many healthcare professionals including physicians now insist that the notion that whole eggs lead to high cholesterol is a myth. This subject could be the subject for an entire article itself. One drawback to whole egg consumption is that some will experience allergies.

The amount of protein needed for body composition goal is not the subject of this document, but to discuss the pros and cons of various protein sources. Protein plays a vital role in the human body and protein toxicity is extremely rare. Exceptionally low-fat proteins without any carbohydrate ingestion could cause toxicity. This theoretically could happen when fat content is so low that it provides little energy and carbohydrates are nonexistent so that the body compensates by attempting to convert protein to a usable energy source. This process requires so much energy that it starves the person causing damage or even death. This situation is extremely rare and requires excessively low fat, high protein, and no carbohydrate situation for an extended timeframe. TPN hopes this article was informative and beneficial. Please visit to browse our blog, obtain more information, become an affiliate, contact us, or take advantage of our free trial membership.