Protein: Basics
What is protein?
All living things are made up of four major groups of organic molecules: carbohydrates, lipids (fats), proteins, and nucleic acids (DNA and RNA). Molecules are composed of atoms joined together by covalent (chemical) bonds. These four main biological molecules are known as “macromolecules.” Macromolecules are large (“macro”) molecules composed of thousands (typically 10,000 or more) atoms.
Protein is a group of nitrogenous organic compounds composed of one or more long chains of amino acids. Amino acids are considered to be the building blocks of protein. They are held together by what is known as peptide bonds. These bonds must be broken down by the body so the amino acids can be absorbed through the small intestine lining into the bloodstream, where they are carried throughout your body to perform a variety of functions.
The body must work harder and use more energy to break the peptide bonds than it does to break down carbohydrates. Once the protein has been disassembled, absorbed, and transported, the amino acids are then reassembled to match and replace our old, worn out proteins. If we are missing or lacking only one essential amino acid from our diet, this process is slowed down or stopped.
Without all the necessary amino acids, the body cannot make the specific protein. The body will wait until the necessary amino acid is available or, if amino acid is in limited supply, may obtain it by breaking down other protein in the body, such as those in muscles and other organs. This can lead to muscle wasting, hair loss, and impaired function of the immune system, nervous system, and more. If the body is unable to get the specific amino acid it needs, then synthesis of the protein will be stopped and the partial protein will be degraded or broken down.
In the case of DNA, a missing amino acid can result in mutations that impair vital functions in the body. Diseases caused by or linked to gene mutations include cystic fibrosis, sickle cell anemia, and haemophilia.
What are the different types of protein?
There are twenty different types of amino acids, which are classified as either “essential” or “non-essential.” Non-essential simply refers to the amino acids the body can create, or synthesize, on its own, while essential refers to those that the body cannot create and must get through food.
Proteins are also categorized depending on their amino acid content. The term “complete protein” is used to describe proteins that possess all the essential amino acids. The term “incomplete protein” is used to refer to proteins that contain limited amounts of amino acids and need to be paired with a “complementary” one.
There are twenty amino acids. The body can manufacture 11 of these on its own, but the other 9 are considered “essential” because they must be obtained through food. Some foods may have more of one amino acid than others, and may not have certain amino acids at all. The particular sequence or combination of amino acids are what determine each protein’s unique structure and specific function.
Why is protein important?
The body breaks the protein down into these amino acids, and uses them for essential functions, including building, strengthening, and repairing muscles and tissues; making antibodies, hormones, and enzymes; transporting substances, such as oxygen through the blood; and mediating cell response. These are only some of the many functions.
“A protein may be classified based on its form and main functions; it can be a globular protein like most enzymes, fibrous protein which are for structural roles; and membrane proteins that serve as receptors or channels for polar or charged molecules to pass through the cell membrane” (1).
Protein accounts for 20% of total body weight, and, next to water, is the most plentiful substance in the body.
What are common sources of protein?
Protein sources can be broken down into two main categories: animal and plant.
Animal sources
Animal protein is considered a “high-quality, complete protein source” due to their amino acid content. However, red meat, processed meat, and butter are all high in saturated fat, and tend to contain a lot of added sodium. Eggs, another often recommended protein source, is high in cholesterol.
The proteins found in animal tissue also contains more sulfur-containing amino acids than the protein in plants. As a result, more sulfuric acid is produced, and can lead to excess acid in the body. The body neutralizes the acid by withdrawing calcium, an alkaline mineral, and uses it to balance the pH of the blood.
Fish used to provide a good protein source. It possessed all the essential amino acids without the saturated fats. It is still highly recommended by many people. Nevertheless, with the recent use of chemicals and pesticides, plus radioactive contamination and other pollution, most fish aren’t safe to eat.
Meat, or animal protein, is the first thing that usually comes to people’s minds when protein is mentioned. Part of this may be due to the fact that consumption of meat has been associated with a higher social class or greater wealth, which has led to it being held in great esteem, and because 19th century research asserted that people needed a minimum of 120 grams of protein per day. This amount has decreased, but remains high, especially since most people are consuming more than is recommended, with many dietitians and health care professionals in Canada recommending 0.8 grams of protein per kilogram of body weight, or an average of 56 grams each day for an adult man, and 46 grams for an adult women (or 10% to 35% of your daily calories).
Furthermore, meat is the first, and sometimes only, protein source that comes to mind because it is comprised of a large amount of protein. Because of this, people have come to believe that meat equals protein; and protein equals meat. Meat is also called a “complete” protein since it contains all of the essential amino acids.
Meat protein sources in particular have been linked to a number of health issues. A high animal protein diet contains twenty times more phosphorus than calcium. Too much phosphorus can cause a number of harmful effects, including calcium being pulled from the bones, hardening of the arteries, and kidney damage. High protein content has been shown to create an acidic environment due to a higher concentration of sulphur containing amino acids. This can also cause calcium to be pulled from bones to help correct the acidity. Another cause for the acidity can be the accumulation of toxic protein metabolic wastes such as uric acid and purines.
Furthermore, animal protein is high in saturated fats and cholesterol, which is linked to heart disease. Animal proteins may also contain hormones and antibiotics and other chemicals and contaminants such as pesticides and herbicides. These substances, including radiation and other pollutants, can be more concentrated in animal products.
Animal protein also tends to contain high levels of harmful bacteria and parasites. These can be destroyed by cooking, but cooking has been shown to coagulate approximately 50% of the protein, making the food less digestible, more coarse, and more inflammatory.
“In essence, cooking meat protein creates a situation in which one actually gets only one-half the protein that is eaten, while the other coagulated half acts as an inflammatory toxin” (2). In addition, animal protein has been shown to cause a surge in insulin release. This insulin surge pulls carbohydrates into the muscle. Excess sugar is converted into body fat. Too much insulin and body fat has been linked with insulin resistance and diabetes.
Plant sources
Plant or vegan sources of protein include organic soybeans, chickpeas, lentils, nuts, seeds, mushrooms, broccoli, oatmeal, seaweed, certain types of algae, flaxseed, and peas.
Most plants are considered an “incomplete” protein. Contrary to popular belief, this does not mean that they are missing essential amino acids. They contain all essential amino acids, but some of them may be in low amounts. This is easily rectified by eating a variety of vegetables. When combined with the correct complementary foods (foods that contain amino acids that the others are missing), they provide all the protein and amino acids that are needed. Wheat is also a source of protein, but it can be hard to digest and loses some of its protein during the digestive process.
While few non-animal protein foods may be considered a “complete protein” by itself, there are some exceptions. One major one is quinoa. Not only does it provide a complete protein source, it also contains a number of health benefits, without the saturated fats. Another major exception is hemp, which also contains a good amount of protein as well as omega-6 and omega-3 fatty acids, fibre, and other vitamins and minerals. Incorporating plant proteins and ancient grains can provide all the protein and essential amino acids that a person needs.
As a group, plant proteins are a “complete” source. You do not need to carefully and rigidly structure or meticulously plan each meal to make certain that you are getting all essential amino acids. As long as you are eating a variety of foods throughout the day, your body can assimilate (absorb) everything it needs.
Other sources of plant protein include almonds, sesame, pumpkin, peas, sunflower seeds, buckwheat, and fruit. Animal based proteins are more similar to ours in that they contain all amino acids in adequate amounts, and, in that sense, are more readily available for protein synthesizing reactions. Plant proteins, since they may not possess all amino acids in noticeable amounts, can take longer since your body has to wait until you consume another plant protein that contains the deficient amino acid.
Nevertheless, it is important to note that, while animal protein may be most similar to ours, it still needs to be disassembled to match our unique protein structure. The long, complex strands of amino acids in animal protein are harder and take longer to break down than the simpler structure of plant protein. The proper digestion, function, and production of amino acids is also reliant on other nutrients, such as carbohydrates, fats, B vitamins, and zinc.
How much protein do we need?
Even though protein is essential for our survival, that doesn’t mean we need to get lots of it. Too much can be just as detrimental as too little. Protein deficiency has been linked with symptoms such as fatigue, hair loss, loss of hair pigment, loss of muscle mass, low body temperature and hormonal irregularities; and protein excess has been linked with symptoms such as causing the immune system to overreact, liver dysfunction from increased toxic residues, bone loss due to increased acidity in the blood, and insulin resistance.
The digestion of protein produces nitrogen as a by-product, which can put a strain on the kidneys as they work to process and eliminate it as urine. Another by-product produced by a high-protein diet and deposited in connective tissues and organs is amyloid. Amyloid has been linked with tissue and organ degeneration and premature aging.
The structure of each form of protein is slightly different. This difference can trigger an immune response in the body, which can lead to allergies. Common protein allergies include casein, the protein in milk; gluten, the protein in wheat and other grains; the particular proteins found in peanuts; and those in shellfish or other seafood (3).
Allergies may also be caused by incompletely digested protein fragments that are absorbed into the bloodstream. Some proteins are more easily absorbed, while others, such as more complex proteins can be harder to fully break down and can take longer to digest, which increases the chance of some of it being incompletely digested.
The word “protein” comes from the Greek word proteios “primary,” from protos “first.” It can be translated as “first place” or “primary importance.” It is an apt description for the prominence that people have placed on this particular nutrient. Rarely do you hear someone say, “Make sure you get enough carbs!” or “Make sure you get enough fats!” (good fats, that is), but you will often hear them say “Make sure you get enough protein!”. Given that body structures, functions and the regulation of the body’s cells, tissues, and organs cannot exist without it, protein certainly deserves a high level of attention. However, people have begun to equate this importance with the idea that we should consume more of it.
“Relative to total calorie intake, only 5-6% dietary proteins is required to replace the protein regularly excreted by the body (as amino acids)” (4). Human breast milk contains an average concentration of approximately 5 percent protein (5). This small amount of protein, with all essential amino acids, is all that is needed for a child during this period of most rapid growth and brain development. A similar concentration of protein can be found in most fruits.
Similarities have often been drawn between apes and humans, and yet “apes, considerably stronger than humans, live on a fruitarian diet that averages between 0.2 and 2.2 percent protein” (6). The Silverback Gorilla is believed to have 30 times the strength of a human. These similarities are interesting to note, whether you believe it is the result of evolution or the hand of a common Creator, because it helps us see that strength is not dependent solely on the amount of protein we consume, but how well we assimilate, or absorb, and use it.
Some people may require more protein than others, depending on their metabolism and activity level, but the human body tends to be more efficient than we are led to believe. So how much protein do we need? Gabriel Cousens, M.D., offers the following advice, “If hair, skin nails, tissues, and, in general, muscle mass, and vitality are not compromised, you are getting enough protein” (7).
This advice may seem generic, but because of the variabilities in humans, there is no exact amount we can base it on. If we are healthy and fit, then we are getting enough. It is important to keep in mind that most of us don’t need as much as society would lead us to believe. By eating a variety of fruits and vegetables, we can get all that we need for proper growth and healing. If you find you need more, then you can add nuts (except peanuts), seeds, and some legumes and ancient grains. Good plant protein sources include quinoa, peas, hemp, kale, and sprouts.
According to charts published by the Economist, the average meat consumption per person in Canada was 98.7 kg (approximately 217 pounds) a year in 2007, and the average meat consumption per person in the United States was 125.4 kg (approximate 276 pounds). The average meat consumption per person worldwide was 38.7 kg (approximately 85 pounds) (8). This amount continues to increase each year.
Another chart (9) indicates that the average dietary protein consumption per person was 77 grams per day; and results from the 2005-2006 National Health and Nutrition Examination Survey (NHANES) revealed that the average dietary protein intake in the United States was 101.9 grams for men and 70.1 grams for women. These amounts are higher than what is even recommended by conventional health care and industry professionals.
Rates of heart disease, cancer, alzheimer’s, osteoporosis, arthritis, diabetes and other deadly diseases are also subsequently high; and continue to rise. These diseases are heavily influenced, and often caused directly by, our diets.
Protein is an essential nutrient, but too much is detrimental to the body. We must achieve balance, and give equal attention to other nutrients, including the often overlooked good (unsaturated) fats. In order to find balance, we must first abolish the idea that meat is the best and only source of protein.
By reducing or eliminating meat consumption, and increasing consumption of fruits, vegetables (particularly dark leafy greens), and other food sources (such as nuts, seeds, and some legumes and ancient grains), we can get all the protein we need without overtaxing or straining our bodies. We can also reduce strain on the earth. Studies reveal that a meat-based diet requires 7 times more land than a plant-based diet, and meat production requires 10 to 20 times more energy per edible tonne than grain production (10).
We need to learn to respect our body’s capabilities. The human body is capable of doing a lot with very little. It is also for that reason that we need to be careful of everything we consume. Eating out at a restaurant only once every week or every two weeks may not seem like a lot to many people, but it can have lasting effects on the body. There are a variety of food resources available to us, and we must choose wisely. Every nutrient counts.
Takeaway
We get calories, or food energy, from three main sources: carbohydrates, protein, and fats. We often hear about getting a “balanced diet,” but we tend to give more emphasis to foods, or nutrients, that taste better, such as sugary or fatty foods.
One nutrient that has been revered for centuries and placed above the others is protein. People don’t often think of it as “protein,” but as meat. This single nutrient has dominated the minds and diets of people throughout the world, but particularly in North America. The United States ranked second in a global ranking of meat consumption per person; and Canada ranked eighth (11).
People love their meat, and that means that they love their protein; or, at least, it means they love their animal protein. Nevertheless, the attention placed on this single nutrient, especially from animal sources, has led us astray from a “balanced” diet. Many of us have forgotten what protein really is, and the role it plays in the body.
References
- http://www.biology-online.org/dictionary/Protein
- Cousens, Gabriel (2013). There is a Cure for Diabetes, Revised Edition, 47.
- http://www.worldofmolecules.com/foods/
- Campbell, T. Colin (2006). The China Study: The Most Comprehensive Study of Nutrition Ever Conducted and the Startling Implications for Diet, Weight Loss and Long-term Health, 308.
- Cousens, Gabriel (2000); Conscious Eating, 312.
- http://treeoflifecenterus.com/high-versus-low-protein-diet/
- Cousens, Gabriel (2013). There is a Cure for Diabetes, Revised Edition, 368.
- http://www.scribd.com/doc/91840616/Meat-Consumption-Per-Person
- http://chartsbin.com/view/1155
- https://www.earthday.ca/giveitup/assets/images/factsheet.pdf
- http://www.scribd.com/doc/91840616/Meat-Consumption-Per-Person