The importance of protein in the human body cannot be overstated. While plants are primarily made of carbohydrates, the human body is mostly made of water, fat, and protein. Regardless of body shape, the human body typically consists of 45-70% water, 14-16% protein, and 18-31% fat, including essential fat (3-12%) and storage fat.1 This means that proteins, or their smaller components called polypeptides, form the majority of the body’s physiological active structures. These protein-based structures are crucial for transportation, communication, digestion, healing, and countless other processes.
Let’s explore these nine essential functions of proteins in the body.
1. Protein provides structure.
Proteins are the building blocks of our bodies. While skeletal muscles—those we voluntarily contract—are well-known to be made of protein, this macronutrient also forms cardiac muscle, which makes up the heart, and smooth muscle, which comprises most organs. Nearly half of bone volume is protein, as it provides the structural matrix that calcium and other minerals fill in. Collagen, keratin, and cartilage are additional protein types that provide structure and strength to skin, tendons, ligaments, and other tissues. Without protein, our bodies would lack the solid framework essential for function and would be more like a jellyfish’s!
2. Protein enables movement and life-sustaining functions.
Protein makes up about 80% of the dry mass of lean tissue. (Water makes up 80% of total muscle weight.) Through contraction and release, skeletal muscles allow us to move, whether it’s walking to get a morning cup of tea or dancing to a favorite song. Beyond all of our conscious movements, proteins are also responsible for the involuntary actions that keep us alive. A beating heart, blinking eyes, breathing lungs, and an active digestive system are all ways bodily protein keeps us alive.
3. Protein repairs tissue.
Given that protein is the primary component of many body parts, it’s also essential for repairing those tissues when they are damaged. Whether it’s muscle recovery after a heavy exercise session, healing a cut, or mending a broken bone, the body uses proteins and polypeptides for blood clotting, tissue growth, and tissue regeneration.
4. Protein helps create energy.
Metabolism—the process of turning food into energy—requires numerous chemical reactions to occur, beginning with digestion and ending with ATP creation. Each of these reactions is triggered by a biological catalyst, an enzyme that is made from protein. These enzymes interact with nutrients and other substrates in the body, transforming them into something new. Without each of these enzymes, our bodies would be unable to create energy, impacting every bodily function.
5. Protein can be used as an energy source.
Although carbohydrates and fats are the body’s preferred energy sources, amino acids can also be used for energy, accounting for 10-15% of energy production under normal circumstances. During starvation or when carbohydrate and fat intake is insufficient—such as with a high-protein diet—the body may break down amino acids for energy. The process of generating ATP, the molecule that stores and transfers energy in the body, from amino acids is not as efficient as producing it from carbs or fats. As well, the nitrogen from each amino acid must be removed from the body via the kidneys.2
6. Protein transports substances throughout the body.
Although each of them serves a unique function, transport proteins all have the same job: move a substance from one location to another within the body. Membrane transport proteins move substances across cell membranes, either into or out of a cell. For example, glucose transporters (GLUTs) move glucose and fructose into cells for energy production, while ATP binding cassette subfamily A (ABCA) members move cholesterol and other fat containing substances out of cells. Blood proteins, such as hemoglobin and lipoproteins, transport vitamins, minerals, fat and gases throughout the body. These transporters ensure that nutrients reach every cell and that waste is efficiently removed.
7. Protein helps maintain fluid and acid-base balance.
Keeping the body’s fluids in the proper places is a delicate act that ensures there is enough but not too much fluid inside the cells, in the space surrounding the cells, and within the circulatory system (i.e., the arteries and veins). Albumin and globulin are two plasma proteins that help regulate fluid pressure within the circulatory system, preventing fluid imbalances. Additionally, our bodies need to maintain the appropriate acid-base balance. Outside of the very acidic stomach environment, the body strives to maintain a pH between 7.35 and 7.45. Proteins play a key role in keeping the inside of cells at the optimal pH.
8. Protein helps protect the body from infections and illnesses.
Protein provides vital immune system support in multiple ways. First, the immune system uses amino acids to create antibodies that fight off infections. As well, some amino acids fuel immune cells and stimulate the immune system to mount a response against a recognized pathogen. Beyond the immune cells themselves, proteins protect the body by providing a strong physical boundary from the outside world, including the tight junctions between intestinal cells and the skin. Proteins also transport vitamins and minerals which support optimal immune function.
9. Protein enables communication throughout the body.
The body employs multiple mechanisms to coordinate the myriad of functions that occur in our bodies and almost all of the messengers are made of amino acids, peptides, and proteins. Hormones carry signals between organs and tissues telling the recipient what needs to happen next. Neurotransmitters and neuropeptides are messengers from one nerve to another. Pheromones are produced in one human and released outside of that person’s body to be received by and have a mutually beneficial impact in another human.
Conclusion
Protein’s roles in the body go far beyond building muscle. From supporting the immune system and regulating hormones to enabling energy production and maintaining fluid balance, protein is essential for overall health. Meeting your daily protein needs ensures that your body has the necessary amino acids to function optimally, supporting everything from movement to communication at the cellular level.
If you want help calculating how much protein you need each day, my guide, “Mastering Your Protein Needs: A Comprehensive Guide,” provides step-by-step instructions, practical lookup tables, and examples of protein-rich meals. Head over to my shop page to purchase your copy today and start taking charge of your nutrition!
Notes:
- These are ranges and do not necessarily reflect all the possible composition percentages for every unique body. Age, athletic status, and other factors will influence the body composition of each person.
- For most healthy individuals, the elimination of excess nitrogen will not cause any health concerns, but may have unwanted consequences for those who have compromised kidney function.
Image by freepik.
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