What are macronutrients?
Macronutrients are the nutrients we need in larger quantities that provide us with energy. They are nutrients that provide calories or energy and are required in large amounts to maintain body functions and carry out the activities of daily life. There are three broad classes of macronutrient namely, proteins, carbohydrates and fats.
Protein as a Macro Nutrients
Protein is a macronutrient that is essential for muscle mass building. They are large biomolecules, or macromolecules, consisting of amino acid residues in one or more long chains. A protein is an extremely complex substance that occurs naturally, consisting of amino acid residues joined by peptide bonds. In all living organisms, proteins are present and include many essential biological compounds like enzymes, hormones, and antibodies. It is commonly found in animal products, though is also present in other sources, such as nuts and legumes.
Protein chemically consists of amino acids, organic compounds that are made of carbon, hydrogen, nitrogen, oxygen or sulphur. Amino acids are the protein building blocks, and the building blocks of muscle mass are proteins. It helps to fuel muscle mass when protein in the body is broken down, which helps metabolism. It helps the immune system to remain strong as well.
Classification of Proteins
Proteins may be divided into two major classes on the basis of their behavior when reacted with water. Proteins can be classified as:
- Simple proteins
- Conjugated proteins
- Derived proteins.
Simple Proteins
On hydrolysis simple protein yield only the amino acids and occasional small carbohydrate compounds. The products obtained upon hydrolysis of simple proteins are all amino acids. Examples are: albumins, globulins, glutelins, albuminoids, histones and protamines.
Conjugated proteins
These are simple proteins combined with some non-protein material in the body. In the case of conjugated proteins other organic and/or inorganic substances are obtained. The non-amino acid portions of conjugated proteins may consist of metals, lipids, sugars, phosphate, or other types of molecules. Examples are: nucleoproteins, glycoproteins, phosphoproteins, haemoglobins and lecithoproteins.
Derived proteins
These are proteins derived from simple or conjugated proteins by physical or chemical means. Examples are: denatured proteins and peptides.
Functions of Proteins in the Body
Protein is an essential substance found in every cell of the human body. In fact, with the exception of water, protein is the most abundant substance in the body. This protein is created by the body using the dietary protein that is eaten by an individual. It is used in many critical systems and thus has to be regularly replaced. This is done by eating food containing protein on a daily basis.
Below are the functions of proteins in the body:
- Repairs and Maintains Body Tissues
- Source of Energy for the Body
- Production of Hormones
- Production of Enzymes
- Transportation and Storage of Molecules
- Antibodies Formation
Repairs and Maintains Body Tissues
The protein is considered the building block of the body. This is named because protein is important to the development of body tissue, including growth and repair. Hair, skin, eyes, muscles and organs are all composed of protein. That’s why children require more protein per pound of body weight than adults; they’re growing and creating new protein tissue. The body uses protein for tissue development and maintenance. It is worth noting that the proteins in the body are in a continuous state of turnover. In normal circumstances, the body breaks down the same amount of protein it requires to build and repair tissues. At other times, it breaks down more protein than it can produce, raising the body’s needs. This generally occurs during times of sickness, during pregnancy and during breastfeeding. People suffering from injuries or surgery, older adults and athletes often need more protein.
Source of Energy for the Body
Protein is a key energy source. If the body absorbs more protein than is required for the preservation of body tissue and other necessary functions, it can be used for energy. If it is not required due to an adequate consumption of other energy sources, such as carbohydrates, the protein can be used to generate fat and become part of the fat cells. Proteins can provide energy to the body. Protein contains four calories per gram, the same amount of energy that carbohydrates provide. The fats provide the most energy at 9 calories per gram. However, the last thing the body needs to use for energy is protein, since this valuable resource is commonly used by the body. Carbohydrates and fats are also more suited to energy supply, as the body retains stores for fuel use. In comparison, they are more effectively metabolized compared to protein. In reality, under normal conditions, protein provides the body with very little of its energy needs. However, in a fasting state (18–48 hours with no food intake), the body breaks down the skeletal muscle so that the amino acids can provide the body with energy. The body still uses broken-down skeletal muscle amino acids when carbohydrate storage is poor. This may occur after a rigorous workout or if the human does not eat enough calories in general.
Production of Hormones
Protein is involved in the processing of certain hormones. These substances help regulate the processes of the body, which include the involvement of many organs. Insulin, a small protein, is an example of a hormone that controls blood sugar. This includes the interaction between organs such as the pancreas and the liver. Secretin, which is another example of a protein hormone. This material aids in the digestive process by inducing the pancreas and the intestine to produce the requisite digestive juices.
Production of Enzymes
Proteins that increase the rate of chemical reactions in the body are enzymes. Actually, without enzymes, most of the required chemical reactions in the body will not proceed effectively. For instance, one type of enzyme works to help digest large molecules of protein, carbohydrates and fat into smaller molecules, while another helps to produce DNA. Proteins that sustain the thousands of biochemical reactions taking place within and outside the cells are enzymes.
The arrangement of enzymes makes it possible for them to combine with other molecules called substrates inside the cell, which catalyze reactions that are important to the metabolism of the body. Outside the cell, enzymes may also work, such as digestive enzymes such as lactase and sucrase, which help digest sugar. For a reaction to take place, some enzymes require other molecules, such as vitamins or minerals. Digestion, energy production, blood clotting and muscle contraction are bodily functions that rely on enzymes. Lack of these enzymes or their improper function can lead to disease.
Transportation and Storage of Molecules
In the transportation of certain molecules, protein is a major factor. Hemoglobin, for instance, is a protein that carries oxygen across the body. To store such molecules, protein is also often used. Transport proteins bring substances into cells, out of cells or inside cells in the bloodstream.
Nutrients such as vitamins or minerals, blood sugar, cholesterol and oxygen are among the substances transmitted by these proteins. Hemoglobin, for instance, is a protein that brings oxygen from the lungs to body tissues. Glucose transporters (GLUT) transfer glucose to the cells, while cholesterol and other fats in the blood are carried by lipoproteins. Protein carriers are special, which means that they can only bind to certain substances. In other words, cholesterol would not be transferred by a protein transporter that moves glucose. There are also storage functions for proteins. Ferritin is a protein for storage which stores iron. Casein, the principal protein in milk that helps babies grow, is another storage protein.
Antibodies Formation
Antibodies that help avoid infection, illness and disease are produced by protein. These proteins recognize antigens such as bacteria and viruses and help kill them. They also function in coordination with the other cells of the immune system. These antibodies, for example, recognise and then surround antigens in order to keep them contained before white blood cells can kill them. Antibodies are protective proteins that have binding sites that enable them to recognise and bind to very specific foreign molecules in their three-dimensional structure. They can help to neutralize and tag them by binding to foreign proteins, promoting their absorption and removal by defensive cells.
Digestion and Absorption (Metabolism) of Proteins
Ingested proteins are first separated by pepsin in the stomach or by trypsin or pancreatic chymotrypsin into smaller fragments. The action of carboxypeptidase, which hydrolyzes one amino acid at a time beginning at the free carboxyl end of the molecule, or aminopeptidase, which splits one amino acid at a time beginning at the free amino end of the polypeptide chain, further reduces these peptides. Via the walls of the gastrointestinal tract, the free amino acids released into the digestive system are then absorbed into the blood stream through the walls of the gastrointestinal tract, where they are then resynthesized into new tissue proteins or catabolised for energy or for more tissue metabolism fragments.
Recommended Dietary Allowance (RDA) for Protein
A moderate 0.8 grams of protein per kilogram of body weight is the recommended dietary allowance (RDA) for protein. The RDA is the sum of nutrients you need to fulfill your basic requirements for nutrition. In a way, not the exact amount you are expected to eat every day, it is the minimum amount you need to keep from getting sick. You should multiply your weight by 0.36 pounds to calculate your daily intake of protein. This translates into 53 grams of protein a day for a 50-year-old woman who weighs 140 pounds and who is sedentary (doesn’t exercise).
Sources of Protein
All food made from meat, poultry, seafood, beans and peas, eggs, processed soy products, nuts and seeds are considered part of the protein group. Most people eat enough food in this group, but they should select leaner and more varied selections.
Besides animal sources, there are several alternative sources of protein, including soy, hemp and whey. Crandall said that all are good options and it comes down to personal preference. For example, whey protein is better for building and regenerating muscle mass, so people looking to bulk up or who exercise a lot may prefer it.
Whey protein is a by-product of the cheese-making process and therefore not vegan. Hemp protein comes from the hemp plant.
Soy protein comes from soybeans and is available in many different forms, including milk, tofu, various meat substitutes, flour, oil, tempeh, miso nuts and edamame..
High-protein foods
Some high-protein meats include:
- Top or bottom round steak (23 grams of protein per 3-ounce serving)
- Lean ground beef (18 grams per 3-ounce serving)
- Pork chops (26 grams per 3-ounce serving)
- Skinless chicken breast (24 grams per 3-ounce serving)
- Turkey breast (24 grams per 3-ounce serving)
- Sockeye salmon (23 grams per 3-ounce serving)
- Yellowfin tuna (25 grams per 3-ounce serving)
High-protein dairy foods include:
- Greek yogurt (23 grams per 8-ounce serving)
- Cottage cheese (14 grams per half-cup serving)
- Eggs (6 grams per large egg)
- 2 percent milk (8 grams per cup)
Some other high-protein foods are:
- Some canned foods, like sardines, anchovies and tuna average around 22 grams of protein per serving
- Navy beans (20 grams per cup)
- Lentils (13 grams per quarter-cup)
- Peanut butter (8 grams per 2 tablespoons)
- Mixed nuts (6 grams per 2-ounce serving)
- Quinoa (8 grams per 1-cup serving)
- Edamame (8 grams per half-cup serving)
- Soba noodles (12 grams per 3-ounce serving)
Complete or Ideal Proteins
People can produce some amino acids, but must get others from food. The nine amino acids that humans cannot produce on our own are called essential amino acids. Essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Protein foods that contain all essential amino acids are called complete proteins, according to Crandall. They are also sometimes called ideal proteins or high-quality proteins. Complete proteins include meat and dairy products, quinoa, hemp seeds, chia seeds and soy.
Many plant-based proteins are not complete proteins. These include beans, grains and legumes as well as vegetables, which contain small amounts of protein. Beans and rice, peanut butter and whole grain bread, and macaroni and cheese are examples of combinations that create complete proteins.
High-Protein Diet
The efficacy and safety of high-protein diets is still being studied. Often, they lead to a quick drop in weight-loss but their overall sustainability is unclear. One of high-protein diet studies found that “although half of the studies showed a higher weight loss with a high-protein diet, three out of four studies with the longest intervention show no statistical difference in weight loss.” Futhermore, high-protein diets can carry some health risks. They usually advocate cutting carbohydrates, which can lead to nutritional deficiencies, fiber deficiencies, headache, constipation, increased risk of heart disease and worse kidney function in those suffering from kidney disease.
Ideal Protein Diet
The Ideal Protein diet is a medically developed diet plan created more than 20 years ago by French doctor Tran Tien Chanh. The Ideal Protein diet is a low-carbohydrate, low-calorie, high-protein diet that aims to aid in weight loss by providing the body with the right amount and kind of protein while also stabilizing blood sugar.
Effects of Protein Deficiencies on Health
Protein is the building block of your muscles, skin, hormones, and enzymes, and plays a crucial role in all tissues of the body. Some protein is found in most foods. As a consequence, in developing countries, true protein deficiency is rare. Some individuals could still be at risk, however. Deficiency leads to numerous health concerns, although low consumption of protein can also be a problem, as over time it may cause subtle changes in your body.
The health conditions resulting from low intake or deficiency of protein are given below:
- Edema
- Fatty liver
- Skin, hair and nail problems
- Loss of muscle mass
- Greater risk of bone fractures
- Stunted growth in children
- Increased severity of infections
- Greater appetite and calorie intake
Edema
A classic symptom of Kwashiorkor is edema, which is characterized by swollen and puffy skin. It is caused by low levels of human serum albumin, which is the most abundant protein in the liquid portion of the blood, or blood plasma, researchers say. One of the key functions of albumin is the maintenance of oncotic pressure, a force that pulls fluid into the blood circulation. Albumin prevents the accumulation of large quantities of fluid in tissues or other body compartments in this way. Extreme protein deficiency leads to less oncotic pressure due to decreased human serum albumin levels. As a consequence, fluid builds up in the tissues, causing swelling. Protein deficiency can lead to fluid accumulation within the abdominal cavity for the same reason. A characteristic symptom of kwashiorkor is a swollen belly. Bear in mind that edema is a symptom of a significant shortage of protein that is unlikely to occur in developing countries.
Fatty Liver
Fatty liver, or fat accumulation in liver cells, is another common symptom of Kwashiorkor. The disorder, left untreated, can evolve into fatty liver disease, causing inflammation, scarring of the liver and likely liver failure. In obese persons, as well as those who drink a lot of alcohol, fatty liver is a common disease. It is unclear why it occurs in cases of protein deficiency, but studies indicate that impaired fat-transporting protein synthesis, known as lipoproteins, can contribute to the disorder.
Skin, Hair and Nail Problems
Deficiency in protein also leaves its mark on the skin, hair, and nails, most of which are made of protein. In infants, for example, kwashiorkor is characterized by flaky or split skin, redness and patches of depigmented skin. There are also common signs of hair thinning, fading hair color, hair loss (alopecia) and brittle nails. However, unless you have a serious protein deficiency, these signs are unlikely to occur.
Loss of Muscle Mass
The muscles are the largest protein reservoir in the body. The body prefers to take protein from skeletal muscles to protect more essential tissues and body functions when dietary protein is in short supply. As a consequence, lack of protein contributes over time to muscle wasting. Even moderate protein insufficiency, particularly in elderly people, may cause muscle wasting. A study of elderly men and women showed that for those who ingested the smallest quantities of protein, muscle loss was greater. This has been supported by other studies showing that an increased intake of protein will delay the degeneration of the muscle that comes with old age.
Greater Risk of Bone Fractures
Muscles are not the only tissues that are impacted by low consumption of protein. Often, the bones are at risk. It can weaken the bones and increase the risk of fractures by not eating enough protein. A research in postmenopausal women showed that a lower risk of hip fractures was associated with higher protein intake. A 69 percent reduced risk was correlated with the highest intake, and animal-source protein tended to have the greatest benefits. Another research found that taking 20 grams of protein supplements a day for half a year slowed bone loss by 2.3 percent in postmenopausal women with recent hip fractures.
Stunted Growth in Children
Not only does protein help maintain muscle and bone mass, but it is also essential for body growth. Deficiency or insufficiency is therefore particularly detrimental to children whose developing bodies need a steady supply. Stunting is actually the most prevalent symptom of childhood malnutrition. Observational studies show a clear association between low protein intake and impaired development. One of the major characteristics of kwashiorkor in children also is stunted growth.
Increased Severity of Infections
Protein deficiency can also affect the immune system by influencing it. The risk or severity of infections, a common symptom of severe protein deficiency, may be increased by impaired immune function. For instance, one of our studies in mice showed that a more serious influenza infection was associated with a diet consisting of only 2 percent protein, compared to a diet providing 18 percent protein. Even a marginally low intake of proteins may impair immune function. Another of our small studies in older women showed a substantial decrease in their immune response after a low-protein diet for nine weeks.
Greater Appetite and Calorie Intake
While one of the signs of serious protein deficiency is poor appetite, the reverse tends to be true for milder types of deficiency. The body attempts to restore protein status by increasing its appetite when protein intake is insufficient, thereby prompting a person to find something to eat. But the desire to feed, at least not for anyone, is not motivated aimlessly by a protein deficiency. It can increase the appetite of people for savory foods selectively, which appear to be high in protein.
Although in times of food scarcity, this may definitely help, the issue is that modern society provides unlimited access to savory, high-calorie foods. Some protein is found in many of these convenience foods. However, relative to the number of calories they contain, the amount of protein in these foods is often considerably poor. As a consequence, low intake of protein could contribute to weight gain and obesity, a concept known as the hypothesis of protein leverage.
