What Is Protein? Functions, Benefits, and Daily Requirements Explained

Protein is one of the key macronutrients your body needs to function optimally. Made up of hundreds or thousands of smaller units known as amino acids, proteins are the fundamental building blocks of your muscles, tissues, enzymes, and hormones [4]. From supporting immune defense to facilitating energy production and tissue repair, proteins are involved in nearly every biological process [1].

Let’s break down what proteins are, their key functions, health benefits, and your daily requirement.

What Is Protein and Why Do We Need It?

Proteins are large, complex molecules composed of long chains of amino acids [1]. The specific sequence and unique 3-dimensional shape of these amino acids determine the protein’s function. They are found in every cell of the body and are considered the basic building blocks of life.

Proteins are involved in numerous essential processes [4]:

• Transporting molecules throughout the body (e.g., hemoglobin)
• Assisting in cell repair and regeneration
• Providing antiviral and antibacterial defense (antibodies)
• Supporting optimal growth and development in children, teenagers, and pregnant women

Without adequate dietary protein, your body cannot perform these functions, which could eventually result in issues such as muscle loss, failure to grow, and reduced organ function [1].

Why Does Your Body Need Protein Daily?

Protein is made up of essential amino acids, nine specific types that your body cannot produce on its own [1]. This means you must obtain them regularly from the food you eat. Protein is naturally present in a wide variety of nutritious foods, including lentils, dairy products, eggs, soy, and whole grains [2].

When you consume protein-rich foods, your body breaks them down into amino acids, which are then used to build and repair tissues, support immune function, produce enzymes and hormones, and maintain muscle mass [4], [5]. Consuming adequate protein daily is crucial to keep these vital processes running efficiently, especially since the body is constantly breaking down and rebuilding protein [6].

How Proteins Function in the Body

Protein should account for 10% to 35% of your daily calories, according to the USDA dietary guidelines [2]. Meeting your protein needs is critical, as its functions permeate every cell in your body.

1. Tissue and Muscle Development

Proteins are fundamental for the formation and maintenance of bodily tissues. Muscle wasting can occur if you do not get enough protein [1]. While strength training causes micro-tears in muscles, the subsequent repair process, which is protein-dependent, leads to muscle expansion. It’s important to note that simply adding more protein to your diet will not result in muscle gain without the stimulus of exercise [3].

2. Enzymes

Enzymes are proteins that bind to specific molecules (substrates) to accelerate chemical reactions (catalysis) [4]. Digestive enzymes like amylase and lipase aid in the digestion of carbohydrates and fats, respectively. Enzymes are essential for:

• Digestion
• Creating energy
• Clotting blood
• Muscle exertion

A deficiency or malfunction of these enzymes can cause disease.

3. Immune System Health

Antibodies are specific protein structures that play a crucial role in the immunological defense against invaders like bacteria and viruses [4]. As a second line of defense, complement proteins help the immune system by breaking down bacterial walls or attracting immune cells (macrophages) to foreign organisms.

4. Energy

During digestion, protein is broken down into amino acids, and each gram provides 4 calories, similar to carbohydrates. However, protein is mainly reserved for building and repairing tissues [5]. Your body primarily uses carbohydrates and fats for energy, resorting to breaking down protein (often from muscle) only during fasting, intense workouts, or when calorie intake is too low [5]. Protein also helps you feel more satiated and fuller for longer, aiding in appetite control.

5. Acts as a Messenger

The majority of your body’s hormones are either proteins or polypeptides (short chains of amino acids) [4]. These hormones, produced by endocrine cells, travel through the bloodstream to target tissues where they attach to functional protein receptors on cell surfaces. Examples of protein-based hormones include:

• Insulin: Signals the cell to absorb glucose.
• Glucagon: Signals the liver to break down stored glycogen into glucose.
• HGH (Human Growth Hormone): Stimulates tissue growth.

6. Provides Structure

Fibrous proteins provide stiffness and rigidity to cells and tissues, giving the body its structural integrity.

• Collagen: The most prevalent protein in the body, it is the structural component of bones, tendons, ligaments, and skin.
• Keratin: A structural protein found in the hair, skin, and nails.
• Elastin: Highly flexible, allowing tissues like the lungs and arteries to return to their original shape after stretching or contracting.

7. Maintains Proper pH

Proteins help maintain the body’s pH balance by acting as buffers. They bind to or release hydrogen ions to stabilize pH levels in blood and other fluids. Hemoglobin in red blood cells, for instance, helps regulate blood pH by buffering excess acid, a process essential for proper cellular function and enzyme activity.

Daily Protein Requirement

The Recommended Dietary Allowance (RDA) for protein for the average healthy adult is 0.8 grams per kilogram (g/kg) of body weight per day [2].

However, protein needs increase significantly during certain periods and for specific populations [6]:

Takeaway

Protein plays an indispensable role in nearly every bodily function from building tissues and supporting immune defense to balancing hormones and providing structure. Whether from plant or animal sources, meeting your daily protein requirement (a minimum of 0.8 g/kg for most adults) is essential for sustaining strength, energy, and overall health [4].

If you’re unsure how much protein you need, speak to a healthcare professional or registered dietitian to personalize your nutrition plan.

Expert Quote:

“Protein is not just for athletes or bodybuilders, but vital for everyone. From hormone production to tissue repair and immune defence, it fuels nearly every process in your body.”

-Dr Anubha Karol

Disclaimer: This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of a qualified healthcare professional, such as a doctor or registered dietitian, before starting, stopping, or changing any treatment, supplement, or diet.

References

[1] MedlinePlus. (n.d.). Protein in diet: MedlinePlus Medical Encyclopedia. Retrieved October 28, 2025, from https://medlineplus.gov/ency/article/002467.htm

[2] U.S. Department of Agriculture (USDA), National Agricultural Library. (n.d.). Food and Nutrition Information Center (FNIC). Retrieved October 28, 2025, from https://www.nal.usda.gov/programs/fnic

[3] Pasiakos, S. M., McLellan, T. M., & Lieberman, H. R. (2014). The effects of protein supplements on muscle mass, strength, and aerobic and anaerobic power in healthy adults: A systematic review. Sports Medicine, 45(1), 111–131. https://doi.org/10.1007/s40279-014-0242-2

[4] Wu, G. (2016). Dietary protein intake and human health. Food & Function, 7(3), 1251–1265. https://doi.org/10.1039/c5fo01530h

[5] Gurina, T. S., & Mohiuddin, S. S. (2020). Biochemistry, protein catabolism. StatPearls Publishing. https://europepmc.org/article/nbk/nbk556047

[6] Millward, D. J. (1995). A Protein-Stat mechanism for regulation of growth and maintenance of the lean body mass. Nutrition Research Reviews, 8(1), 93–120. https://doi.org/10.1079/nrr19950008