Proteins are big molecules cells need to work right. They're made of amino acids. The body's functions and structure depend on proteins. Cells, tissues, and organs can't work without them. Also, muscles, skin, bones, and other parts have lots of protein.
Protein is also key for making enzymes, hormones, and antibodies. Proteins also act as neurotransmitters like hemoglobin which carries oxygen in the blood.
- What are proteins?
Proteins are long chains of amino acids and are the basis of all life. They're like machines that make all living things whether viruses, bacteria, butterflies, jellyfish, or plants.
The human body has about 100 trillion cells. Each cell has thousands of different proteins. These proteins work together so every cell can do its job. Proteins are like tiny machines inside every cell.
- Amino acids and proteins
Proteins are made of amino acids which are protein's building blocks. There are about 20 types of amino acids. They can link in millions of ways to make millions of different proteins, each with its own job in the body. The protein's shape depends on the order of amino acids.
The amino acids the body uses to make different proteins are: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine. They are organic molecules made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.
Amino acids make proteins and also some other important compounds in the human body like creatine, peptide hormones, and some neurotransmitters.
- Types of proteins
There are three types of protein foods:
Complete proteins: These are mostly found in animal foods like meat, dairy, and eggs. These foods have all the essential amino acids.
Incomplete proteins: These are in plant foods like peas, beans, and grains. These foods have at least one essential amino acid missing, so their protein balance is incomplete.
Supplemental proteins: Supplemental proteins are two or more foods with incomplete proteins combined to get complete proteins, like rice and beans or bread and peanut butter.
- What is the role of proteins?
- Proteins play a key role in almost all biological processes. Each protein has a different function. Main roles include building, strengthening, repairing, or replacing parts of the body like tissues.
- Proteins can be
- Structural or building, like collagen
- Hormones like insulin
- Carriers like hemoglobin
- Enzymes like amylase
One strong structural protein is keratin that strengthens protective coverings like hair. Collagen and elastin also have a structural role supporting connective tissues.
- Proteins also form enzymes that work as catalysts which means they speed up chemical reactions. For example, they are vital for breathing in human cells and photosynthesis in plants.
- Protein sources
- Protein is a basic nutrient in our diet, but not all protein we eat is used by the body for building.
All dietary proteins have different amounts of each amino acid. When people eat foods with amino acids, these acids let the body build proteins. If there aren't enough amino acids, the body can't build enough protein to work right.
- There are nine essential amino acids the body can't make: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. These are found in almost equal amounts in complete proteins from animal foods like meat, eggs, and milk.
Plant sources of complete protein include soybeans and quinoa. You can also mix red beans or lentils with brown rice, or peanut butter with whole wheat bread to get complete protein.
Your body might not need all essential amino acids in every meal because you could get what you need from earlier meals.
- What about protein deficiency
- Protein deficiency due to low protein intake is rare. To avoid it, it's recommended that protein makes up 10 to 35 percent of your daily calories if you're an adult. For kids, it's 10 to 30 percent.
- Protein deficiency can also happen if someone has certain health issues like:
- Eating disorders like anorexia nervosa
- Certain genetic conditions
- Late stages of cancer
- Trouble absorbing nutrients because of irritable bowel syndrome (IBS) or stomach surgery.
- Eating too little protein can cause:
- Muscle weakness
- Edema (swelling from fluid retention)
- Hair loss and breakage
- Some skin diseases
- In adults, muscle loss may happen. In kids, growth may stop.
Protein doesn’t have to come only from meat. Seafood, eggs, beans, and legumes also provide protein. The US FDA recommends adults eat 50 grams of protein daily as part of a 2000 calorie diet. Protein amount can be more or less depending on a person’s calorie needs.
- Protein and calories
Protein provides calories since one gram of protein has 4 calories. Keep in mind one gram of fat has 9 calories.
- Protein and weight loss
Some diets recommend eating more protein to lose weight. A 2015 study showed a high-protein diet may help with weight loss.
- Protein supplements
Protein shakes and supplements are popular with athletes but people should use them carefully.
Eating more protein can boost muscle strength and give you a lean, athletic body with great results.
Athletes and bodybuilders must make sure they get enough protein to build and repair muscles. This can be much more than what a regular person needs. There are many protein supplements that help with weight loss and muscle growth and strength.
Still, most athletes can get enough protein from a balanced diet without supplements. Some supplements may have banned or unhealthy substances and there is some proof that too much protein can raise the risk of bone loss or kidney problems.
One study showed that whey protein supplements might affect glucose metabolism and muscle protein.
Another study found that whey protein supplements can reduce body fat and keep muscle when used in a low-calorie diet.
Research from the University of Michigan concluded that whey protein helps cyclists' performance, but another study suggested it might cause bone loss and osteoporosis, though that could be due to other factors.
Anyone using whey protein should not consume more than 1-2 grams per kilo of body weight. Also, whey protein and similar products aren't FDA approved, meaning there’s no oversight on their contents. So anyone thinking about protein supplements for fitness should talk to a sports medicine doctor.
- Protein-related tips
For most people, a healthy varied diet gives enough protein. Getting more protein doesn’t always mean eating extra steak. there are other options to help ensure healthy protein intake.
- Here are some suggestions:
1. Eat a variety of protein foods like fish, meat, soy, nuts, seeds, and so on.
2. Use lean meats, poultry, and low-fat dairy. Remove fat from meat and avoid processed meats because of added sodium.
3. Use cooking methods that don’t add extra fat to your food like grilling.
4. Read the ingredients on protein bars as they can be high in sugar.
5. Make healthier versions of your usual foods. For example, use whole wheat bread instead of white bread and unsweetened peanut butter.
6. Try plant-based proteins like beans, lentils, and soy products.
7. Choose nutrient-rich foods that give you many benefits like fiber.
