Top 10 Foods High In Protein 2016
What are proteins and what do they do?
How Does Your Body Use Proteins?
Proteins play many important roles in the body, from providing structural and mechanical support and maintaining your body’s tissues to creating enzymes and hormones and helping maintain acid-base and fluid balance. They also transport nutrients, assist your immune system, and, when necessary, become a source of energy.
Proteins Provide Structural and Mechanical Support and Help Maintain Body Tissues
Proteins provide much of the structural and mechanical support that keeps you upright, moving, and flexible. Just as wood, nails, and plaster are the behind-the-scenes materials holding up the room around you, several fibrous proteins in your bones, muscles, and other tissues help hold up your body.
Collagen, the most abundant protein in your body, is found in all of your connective tissues, including the bones, tendons, and ligaments, that support and connect your joints and other body parts. This fibrous protein is also responsible for the elasticity in your skin and helps form scar tissue to repair injuries such as wounds.
Two other proteins, actin and myosin, provide mechanical support by helping your muscles contract so you can run, walk, sit, and lie down. The daily wear and tear on your body causes the breakdown of hundreds of grams of proteins each day. For example, the protein-rich cells of your skin are constantly sloughing off, and proteins help create a new layer of outer skin every 25 to 45 days. Because your red blood cells have a short life span-only about 120 days-new red blood cells must continually be regenerated. The cells that line the inner surfaces of your organs, such as your lungs and intestines, are also constantly sloughed off, excreted, and replaced.
In addition to regular maintenance, extra protein is sometimes needed for “emergency repairs.” Protein is essential in healing, and a person with extensive wounds, such as severe burns, may have dietary protein needs that are more than triple his or her normal needs.
Proteins Build Most Enzymes and Many Hormones
When your body needs a reaction to take place promptly, such as breaking down carbohydrates after a meal, it calls upon enzymes, biological catalysts that speed up reactions. Without enzymes, reactions would occur so slowly that you couldn’t survive. Most enzymes are proteins, although some may also have a coenzyme, such as a vitamin, that aids in initiating a reaction.
Each of the thousands of enzymes in your body catalyzes a specific reaction. Some enzymes, such as digestive enzymes, break compounds apart. Other enzymes, such as those used to synthesize proteins, help compounds combine. Enzymes aren’t changed, damaged, or used up in the process of speeding up a particular reaction. Thus, the enzyme is available to catalyze additional reactions. While enzymes expedite reactions, hormones direct them. Many hormones are proteins that direct or signal an activity, often by turning on or shutting off enzymes. Hormones are released from tissues and organs and travel to target cells in another part of your body to direct an activity. There are more than 70 trillion cells in your body, and all of these cells interact with at least one of more than 50 known hormones.
Let’s consider an example of one hormone in action. When your blood glucose level rises after a meal or snack, your pancreas (an organ) releases insulin (a hormone) into your blood, which in turn directs the uptake of glucose in your cells (the activity). If your blood glucose level drops too low, such as between meals, your pancreas (an organ) releases glucagon (a hormone), which promotes the release of glucose from the glycogen stored in your liver (the activity), which in turn raises your blood glucose level.
Proteins Help Maintain Fluid Balance
Your body is made up predominantly of water, which is distributed throughout various body compartments. Proteins help ensure that all this water is dispersed evenly, keeping you in a state of fluid balance.
Normally, your blood pressure forces the nutrient- and oxygen-rich fluids out of your capillaries and into the spaces between your cells. Whereas fluids can flow easily in these spaces, proteins can’t, because they are too big to cross the cell membranes. Proteins attract water, so the proteins remaining in the capillaries eventually draw the fluids back into the capillaries. Hence, protein plays an important role in the movement of fluids and in keeping the fluids balanced among these compartments. (Note: The mineral sodium also plays a major role in fluid balance.)
When fewer proteins are available to draw the fluid from between the cells back into the bloodstream, as during severe malnutrition, a fluid imbalance results. The spaces between the cell become bloated and the body tissue swells, a condition known as edema.
Proteins Help Maintain Acid-Base Balance
Proteins can alter the pH (the concentration of hydrogen ions) of your body fluids. Normally, your blood has a pH of about 7.4, and the fluid in your cells has a pH of about 7.0. Even a small change in the pH of your blood in either direction can be harmful or even fatal. With a blood pH below 7.35, a condition called acidosis sets in, which can result in a coma. A blood pH above 7.45, known as alkalosis, can result in convulsions.
Proteins act as buffers and minimize the changes in acid-base levels by picking up or donating hydrogen ions in the blood. Should your blood become too acidic, some of the amino acid side chains in the proteins will pick up excess hydrogen ions. Other side chains can donate hydrogen ions to your blood if it becomes too basic.
Proteins Transport Substances throughout the Body
Transport proteins shuttle oxygen, waste products, lipids, some vitamins, and sodium and potassium through your blood and into and out of cells through cell membranes. Hemoglobin acts as a transport protein that carries oxygen to cells from the lungs. Hemoglobin also picks up carbon dioxide waste products from cells for transport to your lungs to be exhaled from your body. Once in your blood, vitamin A travels to your liver and is bound to yet another protein to be transported to your cells.
Transport proteins in cell membranes form a “doorway” that allows substances such as sodium and potassium to pass in and out of cells. Substances that are not lipid-soluble or that are simply too big to pass through the lipid-rich membrane have to enter the cell through a protein channel.
Proteins Contribute to a Healthy Immune System
Your immune system works like an army to protect your body from foreign invaders, such as disease-causing bacteria and viruses. Specialized protein “soldiers” called antibodies eliminate these potentially harmful substances. Once your body knows how to create antibodies against a specific invader, such as a virus, it stores that information and you have immunity to that pathogen. The next time the invader enters your body, you can respond very quickly (producing up to 2,000 precise antibodies per second!) to fight it. When this rapid immune response works efficiently, it prevents the virus or other invader from multiplying to levels high enough to make you sick.
Sometimes, your body incorrectly perceives a nonthreatening substance as an invader and attacks it. This perceived invader is called an allergen. Food allergens are proteins in a food that are resistant to being broken down by heat during cooking or by the gastric juice and enzymes in the body. Individuals who react to these allergens are diagnosed with food allergies. You will learn more about food allergies.
Proteins Can Provide Energy
Because proteins provide 4 calories per gram, they can be used as an energy source. However, the last thing you want to do is use this valuable nutrient, which plays so many important roles in your body, as a regular source of fuel, especially since carbohydrates and fats are far better suited for providing energy. When your diet contains adequate amounts of calories from carbohydrates and fat, proteins are used for their other important roles.
When your diet doesn’t provide adequate amounts of calories-for example, in times of starvation-your body begins to break down its protein, mainly from muscles, into its amino acid components. The carbon skeletons of the amino acids are used for energy and for gluconeogenesis, the creation of glucose from noncarbohydrate sources. (Remember that your brain and nervous system need a minimum amount of glucose to function properly.) However, when proteins are used for energy, they create waste products that must be eliminated from your body, which is particularly burdensome for your liver and kidneys.
Protein Improves Satiety and Appetite Control
In addition to the structural and functional roles protein plays in the body, protein also helps increase satiety, the feeling of fullness, after a meal more than either carbohydrate or fat.10 Eating a meal that contains a good source of protein will leave you more satisfied than a meal containing the same amount of calories but with the majority of them coming from carbohydrate. Although the mechanism behind protein’s effect on your appetite is not yet known, some research studies suggest that it may be due to several factors, such as changes in appetite-suppressing hormones in the body, how the body metabolizes protein, and the levels of the amino acids in the blood.
Including protein in each meal can help control your appetite, which in turn can help you maintain a healthy weight.
Message
Proteins play many important roles in the body, including: (1) structural and mechanical support, (2) building enzymes and some hormones, (3) maintaining fluid balance, (4) maintaining acid-base balance, (5) transporting substances throughout the body, (6) providing antibodies for a strong immune system, (7) providing energy, and (8) promoting satiety.
Terms:
Collagen – A ropelike, fibrous protein that is the most abundant protein in your body.
Connective tissue – The most abundant tissue type in the body. Made up primarily of collagen, it supports and connects body parts as well as providing protection and insulation.
Enzymes – Substances that act as catalysts and speed up reactions.
Catalysts – Substances that aid and speed up reactions without being changed, damaged, or used up in the process
Coenzyme – Substances, often vitamins, that are needed by enzymes to perform many chemical reactions in your body.
Hormones – Protein- or lipid-based chemical messengers that initiate or direct a specific action. Insulin, glucagon, and estrogen are examples of hormones.
Fluid balance – The equal distribution of water throughout your body and within and between cells.
Edema – The accumulation of excess fluid in the spaces surrounding your cells, which causes swelling of the body tissue
Buffers – Substances that help maintain the proper pH in a solution by attracting or donating hydrogen ions.
Transport proteins – Proteins that carry lipids (fat and cholesterol), oxygen, waste products, and vitamins through the blood to various organs and tissues. Proteins can also act as channels through which some substances enter cells.
Antibodies – Proteins made by your body to bind to and neutralize foreign invaders, such as harmful bacteria, fungi, and viruses, as part of the body’s immune response
Immunity – The state of having built up antibodies to a particular foreign substance so that when particles of the substance enter the body, they are destroyed by the antibodies.
Proteins as Transport Channels
Transport proteins form a channel, or doorway, through which substances such as sodium and potassium can move from one side of the cell membrane to the other.
Outside cell – Transport protein; Potassium
Inside cell – Sodium binds to transport protein; Transport protein releases sodium outside of cell; Potassium binds to transport protein; Transport protein releases potassium inside the cell
Protein Power
Melt a slice of reduced-fat cheese between slices of a toasted whole-wheat English muffin for a protein-packed, portable breakfast.
Spread peanut butter on apple slices for a sweet, stick-with-you morning snack.
Add high-fiber, protein-rich chickpeas to your lunchtime salad.
Roast beef is the best-kept lunchtime secret.
It’s naturally lean and makes a mean sandwich filler.
Stuff a baked potato with cottage cheese, steamed broccoli, and a sprinkling of Parmesan cheese for a meal filled with protein and good nutrition
An Enzyme in Action
Enzymes speed up reactions in your body, yet they aren’t changed, damaged, or used up in the process.
1. A compound approaches a specific enzyme.
2. The compound binds to the enzyme.
3. The enzyme changes shape
4. Two products are released and the enzyme is available for another reaction.
The Many Roles of Proteins
Role of Proteins How It Works
1. Provide structural and mechanical support and maintenance
Proteins are your body’s building materials, providing strength and flexibility to your tissues, tendons, ligaments, muscles, organs, bones, nails, hair, and skin. Proteins are needed for the ongoing maintenance of your body.
2. Build enzymes and hormones
Proteins are needed to make most enzymes that speed up reactions in your body and many hormones that direct specific activities, such as regulating your blood glucose level.
3. Maintain fluid balance Proteins play a major role in ensuring that your body fluids are evenly dispersed in your blood and inside and outside your cells.
4. Maintain acid-base balance
Proteins act as buffers to help keep the pH of your body fluids balanced within a tight range. A drop in pH will cause your body fluids to become too acidic, whereas a rise in pH can make them too basic.
5. Transport substances
Proteins shuttle substances such as oxygen, waste products, and nutrients (such as sodium and potassium) through your blood and into and out of your cells.
6. Affect antibodies and the immune response
Proteins create specialized antibodies that attack pathogens in your body that can make you sick.
7. Provide energy
Because proteins provide 4 calories per gram, they can be used as fuel or energy in your body.
8. Improves satiety Protein increases satiety, which can help control your appetite and weight.
Proteins play an important role in keeping your skin healthy and your nails strong.
