What Does Protein Do? A Guide to This Essential Nutrient
Medically reviewed by Suzanne Fisher, RD
Protein is an essential macronutrient that forms the building blocks of every cell in your body. When you consume animal or plant-based protein, your body breaks it down into amino acids. Your cells use amino acids to build and repair body tissues like muscle, skin, organs, and bones. Proteins also provide fuel for energy, support immune function, and regulate vital body processes like metabolism, growth, and digestion.
This article discusses the numerous functions of protein in the human body, its effect on body weight, protein-rich foods, and ideal intake levels. It also covers what happens to your body when you consume too much protein.
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Protein Functions in the Human Body
Protein is the workhorse of the body’s cells and is crucial for maintaining a healthy and well-functioning body. Made up of amino acid chains, protein plays a role in virtually every body process, from building and repairing tissues to fueling metabolism and regulating the body’s numerous biochemical reactions.
Build and Repair Tissue
One of protein’s primary roles is forming and maintaining the structural foundation of your body: muscles, bones, skin, hair and nails, and internal organs. Every cell in your body contains protein—it is essential for the structure and function of every part of the human body. The amino acids that make protein are the raw materials for building and repairing body tissues.
Your body continuously breaks down protein; this continuous turnover (replacing old proteins with new ones) is essential for repairing and regenerating body tissues. There are times when your protein needs increase—such as when recovering from an illness, surgery, or injury. Older adults and pregnant or breastfeeding people need more protein to maintain optimal health.
Regulate Metabolic Processes
Protein is the basis for creating enzymes, which are important for every biochemical reaction and function in your body.
Enzymes are complex proteins that act as catalysts for chemical reactions in the body related to energy production, growth, nutrient digestion, muscle function, and blood clotting. They also play a role in the body’s detoxification process, helping lower your risk of some diseases and conditions (e.g., heart disease, Alzheimer’s disease).
Act as a Chemical Messengers
Hormones act as chemical messengers that travel in the bloodstream, regulating many body processes. Many hormones, called peptide hormones, are made up of proteins. Peptide hormones are critical in regulating growth, mood, and metabolism. Examples of protein-based hormones include:
Insulin: Promotes the uptake of glucose into cells as an energy source.
Epinephrine (adrenaline): Helps maintain cardiovascular health and triggers the body’s fight-flight reactions.
Oxytocin: Known as the “love hormone,” oxytocin plays a role in human behaviors such as trust, romantic and familial attachments, and sexual arousal.
Thyroxine: A thyroid hormone that regulates the body’s heart, metabolic rate, digestive function, brain development, and more.
Human growth hormone: Promotes growth in children and maintains the body’s structure and metabolism in adults.
Support the Immune System
Many immune system components are protein-based, making protein vital for optimal immune function and protecting your health. Cytokines, for example, are small proteins that control the growth and activity of other immune cells. When cytokines are released into the bloodstream, they send signals and regulate the action and function of other immune cells to protect the body from any potential threat. Cytokines also play a role in the body’s inflammatory response.
Antibodies are proteins circulating through the bloodstream that identify and neutralize foreign substances, such as bacteria and viruses, that may threaten your health.
Maintain Fluid Balance
Proteins help maintain and regulate the body’s fluid balance. Albumin is a protein that attracts and holds water within the bloodstream. This creates a pressure called oncotic pressure, which counteracts the outward pressure of fluids pressing against blood vessel walls, preventing fluid from leaking into the surrounding tissues.
Albumin also helps regulate the movement of lymphatic fluid, helping prevent tissue edema (swelling) and ensuring proper fluid distribution throughout the body.
Protein Sources and How to Eat More
Getting enough protein in your diet is an excellent way to support your overall health. There are many food sources of protein, including animal and plant-based protein foods. Whatever you prefer, eating various protein foods is the best way to ensure your body gets the nutrients it needs.
Animal-Based Proteins
Animal proteins, like those found in meat, poultry, fish, eggs, and dairy, are considered complete proteins. Animal protein foods contain all nine essential amino acids, which your body cannot produce on its own, and you must get through the foods you eat.
Animal-based protein foods include:
Meats: Beef, pork, goat, ham, lamb, or game meats (e.g., deer, bison)
Poultry: Chicken, turkey, Cornish hen, duck, pheasant
Seafood: Fish (e.g., tilapia, flounder, haddock, tuna, salmon) and shellfish (e.g., scallops, lobster, oysters, shrimp)
Dairy: Cow’s milk, cheese, yogurt
Eggs
Plant-Based Proteins
Plant-based proteins are incomplete proteins, meaning they lack one or more essential amino acids. By incorporating different plant protein sources into your meals, you can consume complementary proteins to ensure you consume all the essential amino acids.
Plant-based protein foods include:
Nuts and seeds: Almonds, walnuts, cashews, and pistachios; chia, pumpkin, sesame, and sunflower seeds
Soy products: Tofu, tempeh
Beans, peas, and lentils: Black, garbanzo, kidney, lima, pigeon, split, black-eyed peas, and lentils
Protein: Recommended Dietary Allowance
The U.S. Department of Agriculture (USDA) guidelines recommend that between 10% and 35% of an adult’s daily caloric intake should come from protein sources. One gram of protein is four calories, so if you consume 2,000 calories daily, you could eat between 100 and 400 calories of protein.
Remember that these are general recommendations; how much protein you need depends on your age, sex, activity level, and overall health.
Boosting Your Protein Intake
Getting enough protein is vital for maintaining good health. Here are some tips to boost your protein intake:
Start your day with protein: Eat a protein-rich breakfast with eggs, yogurt, or a protein smoothie.
Snack smart: Choose snack foods that are good sources of proteins, such as a handful of nuts, seeds, or edamame.
Add protein to every meal: Include protein sources, including salads, stir-fries, and soups.
Rotate: Mix your protein sources throughout the week to ensure you consume the essential amino acids and satisfy your palate.
Protein Role in Weight Loss or Weight Gain
While protein doesn’t directly cause weight loss or gain, it does affect your appetite, metabolism, and body composition (e.g., muscle mass)—all factors that play a role in weight management.
Satiety and Appetite Control
Compared to carbohydrates and fats, protein is more satiating, meaning it can make you feel fuller for longer periods, which may help with appetite control and promote weight loss. Research shows that people with higher-protein diets tend to consume fewer calories overall.
Metabolism Boost
Digesting and metabolizing protein requires more energy than carbohydrates or fats, leading to a slight increase in calorie burning, known as the thermic effect of food. This may contribute to a small but measurable calorie deficit over time.
Muscle Building
Muscle tissue burns more calories at rest compared to fat. Higher protein intake helps preserve muscle mass during weight loss, which may boost metabolism and maintain calorie burning. However, excessive protein intake beyond recommended levels won’t accelerate weight loss but may contribute to weight gain.
What Does Too Much Protein Do?
While protein is a foundational nutrient for health, exceeding the recommended intake may harm your health. Moderation is key, and following recommended protein intake guidelines is the best approach to protein consumption.
Effects of a Heavy Meat Diet
Diets high in certain types of protein, including red and processed meats, can put you at risk of certain diseases, including heart disease, chronic kidney disease, and cancer.
Heart disease: Research findings show a strong link between diets high in red meat and processed meat consumption and the risk of cardiovascular (heart) disease, stroke, and heart failure.
Cancer: Some studies suggest a diet high in red and processed meats increases the risk of colorectal, prostate, and pancreatic cancers.
Kidney disease: Excess protein intake may adversely affect kidney function, as the kidneys must work harder to filter and remove waste products. A high-meat diet can be dangerous for people with kidney diseases.
Protein Shakes
Protein shakes can be a convenient way to add protein to your diet, but relying on them as a sole protein source can be more harmful than helpful. Protein shakes are powders made with animal or plant-based sources (e.g., casein, whey, soy, hemp).
While fitness buffs may tout them as a magic bullet for fueling your body pre or post-workout, consuming protein shakes and powders comes with health risks.
A 2018 study found high amounts of heavy metals like arsenic, lead, and mercury in several popular protein shakes. These contaminants, likely from contaminated soil or water used in ingredient production, can lead to organ damage, immune system dysfunction, and harm your nervous system.
And while many protein shakes may help increase your protein intake, they also add sugars, such as fructose corn syrup or artificial sweeteners, that can contribute to weight gain, disrupt a healthy gut microbiome, and increase the risk of type 2 diabetes and heart disease.
Summary
Beyond providing sustenance, protein is an essential macronutrient your body needs for optimal functioning and maintenance. Protein builds and repairs body tissues like muscles, skin, and bones, provides energy, supports immune function, and regulates important body processes. While protein is important, too much can lead to adverse health outcomes, especially high amounts of red and processed meats. Consuming protein from animal and plant-based sources is the best way to ensure your body gets the protein and other nutrients it needs to support your health and well-being.
Read the original article on Verywell Health.
