Proteins are large molecules which need to work properly in our cells. These are composed of amino acids. Our bodies ‘structure and function depends on the proteins. Without them the regulation of the cells, tissues, and organs of the body can not occur.
Muscles, skin, bones, and other parts of the human body contain substantial protein intakes, including enzymes, hormones, and antibodies.
Proteins act as neurotransmitters, too. Hemoglobin is a protein which carries oxygen in the blood.
What are proteins?
Proteins are long amino acid chains which form the basis of all life. They are like machines that render all living things, whether they behave as viruses, bacteria, insects, jellyfish, plants or humans.
The human body is composed of some 100 trillion cells. Each cell contains thousands of distinct proteins. This allow each cell to do its work together. The proteins inside the cell are like diminutive machines.
Amino acids and proteins
Protein is composed of amino acids, and amino acids are the protein building blocks. There are approximately 20 amino acids.
These 20 amino acids can be organized in millions of different ways, each with a particular role in the body, to produce millions of different proteins. The structures vary by the order the amino acids combine in.
The 20 different amino acids used by the body for the synthesis of proteins are: alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine.
Amino acids are organic, carbon, hydrogen, oxygen, nitrogen, and occasionally sulfur molecules.
It is the amino acids in the human body that synthesize proteins and other essential compounds like creatine, peptide hormones and certain neurotransmitters.
Types of protein
We sometimes hear that there are three types of protein foods:
Total protein: It includes all the essential amino acids in these foods. They occur mainly in animal feeds, such as poultry, dairy and eggs.
Incomplete proteins: These foods contain at least one essential amino acid, thus the proteins lack balance. Plant foods, including peas, beans, and grains, contain often incomplete protein.
Complementary proteins: these apply to two or more foods that contain incomplete proteins that can be combined by people to provide full protein. Examples include rice and beans, or peanut buttered bread.
What do proteins do?
Proteins play a role in almost every biological cycle, and they differ greatly in function.
The key protein functions in the body are constructing, strengthening and restoring or replacing items, such as tissue.
They can be:
- structural, like collagen
- hormonal, like insulin
- carriers, for example, hemoglobin
- enzymes, such as amylase
These are all proteins.
Keratin is a structural protein that strengthens protective coatings like fur. Collagen and elastin both have a structural role, and protect connective tissue as well.
Most enzymes are proteins and are catalysts, indicating that they accelerate chemical reactions. For example, they are required for respiration in human cells, or photosynthesis in plants.
Protein is one of the basic nutrients or macronutrients in the human diet, although not all of the nutrition that we consume in our body is converted into nutrition.
When people eat foods containing amino acids, these amino acids help the body to produce proteins, or synthesize them. If we don’t eat any amino acids, we won’t synthesize enough protein to make our bodies function properly.
There are also nine essential amino acids that are not synthesized by the human body, so they must come from the diet.
All food proteins contain some but in different proportions of each amino acid.
Gelatin is unique because it contains a high proportion of a few amino acids but not the entire range.
The nine basic acids not synthesized by the human body are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophane, and valine.
Foods that contain approximately equal proportions of these nine essential acids are considered full proteins. Full proteins come primarily from animal sources including milk, poultry, and eggs.
Soy and quinoa are whole protein vegetable sources. Complete protein is also provided by mixing red beans or lentils with wholegrain rice or peanut butter with wholemeal bread.
At-meal the body doesn’t need all the necessary amino acids, as it can use amino acids from recent meals to form full proteins. If you have ample protein all day long, there’s no chance of a deficiency.
In other words, protein is the required nutrient but amino acids are what we really need.
Protein deficiency due to insufficient protein consumption in the diet is rare as an uncommon disease in the U.S. The 2015–2020 American Dietary Guidelines suggest that 10 to 35 per cent of the daily calories of an adult will come from protein. It’s 10 to 30 per cent for kids.
According to the Centers for Disease Control and Prevention (CDC), men in the United States get on average 16.1 percent of their calories from protein and women get 15.6 percent from protein.
A lack of protein in the diet, however, is a matter of concern worldwide, especially when it affects children. It can cause malnutrition problems, such as kwashiorkor and marasmus. These are potentially life-threatening.
A deficiency can also arise if a person has a health condition, such as:
- an eating disorder, for example, anorexia nervosa
- certain genetic conditions
- the later stages of cancer
- difficulty absorbing nutrients, due, for example, to irritable bowel syndrome (IBS) or gastric bypass surgery
Very low protein intake can lead to:
- weak muscle tone
- edema, which is swelling due to fluid retention
- thin and brittle hair
- skin lesions
- in adults, loss of muscle mass
- in children, stunted growth
Biochemical tests may show low serum albumin and hormone imbalances.
The exact amount of protein a person needs remains a subject of discussion.
As part of a 2000-calorie diet, the FDA recommends that adults eat 50 grams of protein a day. Depending on your calorie needs, the daily value of a individual can be greater or lower.
However, it is difficult to determine exact numbers, since a number of variables, such as age, gender, level of activity, and status, such as pregnancy, play a role.
Many factors include the proportion of amino acids in different protein foods and the digestibility of the amino acids in individuals. How the protein metabolism influences the need for protein intake remains uncertain as well.
The following foods should provide around 1 ounce of protein per serving, described below, according to the U.S. Department of Agriculture (USDA):
- one ounce lean meat, poultry, seafood
- one ounce of meat, poultry, or seafood
- one egg
- one tablespoon of peanut butter
- half an ounce of nuts or seeds
- one fourth of a cup of cooked beans or peas
For most people over the age of 9, the USDA recommends eating between 5 and 7 ounces of protein foods a day.
They have a calculator to make it easy to find out how much protein a person requires and other nutrients.
Protein and calories
Protein yields calories. One gram of protein is composed of 4 calories. One gram of fat contains nine calories.
The average American consumes about 16 percent of its calories from protein, be it animal or plant.
Protein and weight loss
Some diets suggest to eat more protein to lose weight.
Results of a review published in 2015 indicate that adopting a specific form of high-protein diet may promote weight loss but further research is required to decide how to effectively enforce such a diet.
Adding protein to an established diet is unlikely to contribute to weight loss, but substituting protein for fat and sugar may help. It may have a detrimental impact to substitute high-fiber foods such as fruit, vegetables, and whole grains with protein foods.
When making this kind of transition, people will understand their overall consumption and dietary patterns, and consult with a doctor before going ahead.
Protein shakes and foods
Eating more protein will improve muscle strength and encourage a lean, fat-burning physique. This, however, depends on the total intake and activity rates of the person in the food.
Athletes and bodybuilders need to ensure that they have adequate protein to build and rebuild muscle, and this could be more than the required amount.
There is currently a large variety of protein supplements available, many claiming to promote weight loss and improve muscle mass and strength.
Most athletes, however, can get enough protein from a healthy diet without needing supplement.
Some supplements can also contain substances which are banned or harmful.
There is some evidence that the risk of osteoporosis or kidney problems may increase by too much protein.
One study indicated that whey protein could affect the metabolism of glucose and the synthesis of muscle protein. Other work suggests that if used in a reduced-calorie diet, at least one form of whey supplement will minimize body fat and retain lean muscle.
One study has shown that whey protein improved efficiency in cyclists, according to the University of Michigan (UOM), and while another has indicated that it may contribute to bone loss and osteoporosis, although this may also be due to other factors.
The UOM states that for every 2.2 pounds of body weight, anyone using whey protein will eat no more than 1.2 grams.
Additionally, whey protein and related products have no FDA clearance as supplements. This means that power over their contents is minimal or no.
Anyone considering taking protein supplements for health purposes should speak to a professional who specializes in sports medicine.
A diverse and balanced diet should provide enough protein for most people.
Eating more steak does not automatically mean that protein intake. Certain options will help you maintain a balanced intake of proteins.
Here are some recommendations:
- Eat a variety of protein foods, choosing from fish, meat, soy, beans, tofu, nuts, seeds, and so on.
- Choose low-fat meat, poultry, and dairy products, and trim the fat from the meat. Opt for smaller portions and avoid processed meats, as they have added sodium.
- Use cooking methods that do not add extra fat, such as grilling.
- Check the ingredients in “protein bars,”as they can also be high in sugar.
- Opt for healthier versions of your usual favorites, for example, wholemeal rather than white bread and unsweetened peanut butter.
- Experiment with plant-based proteins, such as beans, lentils, and soy products.
- Choose nutrient-rich foods that provide other benefits, such as fiber.
Is it dangerous to use protein shakes and whey protein in a weight-loss diet?
Protein shakes and whey protein are acceptable to incorporate in a healthy weight-loss diet plan, as long as the total daily protein intake does not consistently exceed a person’s recommended daily allowance for protein, and as long as a person is replacing other sources of calories with proteins, and not simply adding extra calories to their day.
Greatly exceeding protein needs can be damaging to a person’s health, including kidney damage and dehydration. Katherine Marengo LDN, RD
Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.