What is the role of protein in health and disease?

January 14, 2026 •

5 min read

With over 10,000 different types found in the body, protein is a fundamental building block of life. Understanding what is the role of protein in health and disease is crucial for maintaining bodily function, from cellular repair to immune response.

Quick Summary

Protein is essential for building and repairing tissues, catalyzing metabolic reactions, and maintaining fluid balance. Both inadequate and excessive protein intake can have significant health consequences, highlighting its central importance for overall well-being.

Key Points

Fundamental Building Block: Protein, composed of amino acids, is essential for building and repairing every cell and tissue in the body.
Metabolic Catalyst: Many proteins function as enzymes, speeding up vital biochemical reactions necessary for metabolism and energy production.
Immune Defense: Antibodies, which are a type of protein, are critical components of the immune system that defend against infections.
Hormonal Messenger: Certain protein-based hormones, like insulin, transmit signals that coordinate vital biological processes throughout the body.
Deficiency Consequences: Severe protein deficiency can lead to conditions like kwashiorkor and marasmus, causing fluid retention, muscle wasting, and stunted growth.
High-Protein Diets: These can support weight management through increased satiety and muscle preservation, but long-term excess can strain the kidneys.
Dietary Source Matters: Plant-based proteins are associated with a reduced risk of chronic diseases and are typically higher in fiber, while animal sources offer complete amino acid profiles.

The Core Functions of Protein

Proteins are large, complex molecules essential for the structure, function, and regulation of the body's cells, tissues, and organs. Composed of amino acids, they perform an astonishing variety of tasks that are foundational to life. The name protein itself comes from the Greek word proteos, meaning "primary" or "first place," a testament to their importance.

Growth and Maintenance

One of the most well-known functions of protein is its role in growth and maintenance. The body constantly breaks down and repairs tissues, and protein is the key nutrient for this process. This function is particularly critical during periods of rapid growth, such as childhood, pregnancy, and lactation. It is also vital for individuals recovering from illness, injury, or surgery, and for athletes who experience high levels of muscle tissue breakdown.

Enzymes and Metabolic Reactions

Enzymes, which are proteins, act as catalysts for the thousands of biochemical reactions that occur within our cells. They speed up processes that are essential for metabolism, such as digestion, energy production, and blood clotting. Without these enzymes, many bodily functions would happen too slowly to sustain life.

Hormones and Signaling

Certain proteins and peptides function as hormones, which are chemical messengers that coordinate biological processes between different cells, tissues, and organs. Hormonal proteins like insulin and glucagon regulate blood sugar levels, while human growth hormone stimulates overall growth.

Structural Support

Fibrous proteins provide structure and support for cells and tissues. Examples include:

Collagen: The most abundant protein in the body, it is the main structural protein for bones, tendons, ligaments, and skin.
Elastin: A highly flexible protein found in tissues like the lungs and arteries, allowing them to stretch and return to their original shape.
Keratin: The structural protein that makes up hair, skin, and nails.

Immune Function

Proteins are crucial for a robust immune system. Antibodies, also known as immunoglobulins, are specialized proteins that bind to specific foreign particles, such as viruses and bacteria, to help protect the body from illness. A deficiency in protein can compromise the immune system, making a person more susceptible to infections.

Fluid and pH Balance

Blood proteins like albumin and globulin play a vital role in maintaining the body's fluid balance. They attract and retain water in the blood vessels, preventing fluid from leaking into the spaces between cells. Additionally, proteins help regulate the concentration of acids and bases in the blood, acting as buffers to maintain the stable pH necessary for survival.

Transport and Storage

Many proteins are involved in transporting and storing nutrients and other molecules throughout the body. For example, hemoglobin is a protein in red blood cells that transports oxygen from the lungs to the tissues. Ferritin is a storage protein that holds iron, while lipoproteins transport fats and cholesterol.

Protein and Health: Deficiency vs. Excess

Both insufficient and excessive protein intake can lead to health problems. The ideal intake depends on an individual's age, activity level, and health status.

The Risks of Protein Deficiency

In developed nations, severe protein deficiency is rare but can occur in certain conditions. In developing regions, it is a serious issue, especially for children.

Kwashiorkor: A form of malnutrition caused by a severe protein deficiency, characterized by fluid retention leading to a swollen abdomen, as well as apathy and poor growth.
Marasmus: Another severe malnutrition condition resulting from a general lack of both calories and protein, leading to extreme emaciation.
Other symptoms: Lesser degrees of deficiency can cause muscle wasting, weakened immunity, and brittle hair and skin lesions.

The Risks of Excess Protein Intake

While many people focus on getting enough protein, excessive intake can also pose risks, particularly over the long term. A high-protein diet may place a significant acid load on the kidneys, potentially exacerbating existing kidney conditions. Chronic excessive protein intake may also increase calcium loss and could lead to kidney stones. However, recent studies suggest a higher protein diet, especially from plant sources, does not typically harm heart or bone health in healthy individuals.

The Role of Protein in Preventing Chronic Disease

Protein intake and source are significant factors in the prevention and management of chronic diseases. For instance, diets rich in plant-based proteins from legumes, nuts, and seeds are linked to a reduced risk of chronic illnesses such as cardiovascular disease and type 2 diabetes. Protein's ability to promote satiety is also valuable for weight management and obesity-related conditions.

Potential Benefits of Adequate Protein:

Cardiovascular Health: Replacing red and processed meats with lean or plant-based proteins can help lower the risk of heart disease by reducing saturated fat intake.
Diabetes Management: Protein has a slower effect on blood sugar compared to carbohydrates, helping to stabilize levels.
Muscle Preservation: Adequate protein intake is vital for maintaining muscle mass and strength, particularly as people age and face conditions like sarcopenia.
Inflammation Reduction: Bioactive peptides found in some proteins possess anti-inflammatory properties, which can help combat chronic inflammation.

Comparison of Protein Sources

Understanding the differences between animal-based and plant-based protein sources is key to making informed dietary choices. A protein source is considered "complete" if it contains all nine essential amino acids.


Feature	Animal-Based Protein	Plant-Based Protein
Completeness	Generally complete, containing all essential amino acids.	Most are incomplete, but some exceptions exist (e.g., soy, quinoa).
Essential Amino Acids	Abundant in all essential amino acids.	Can be low in one or more essential amino acids, but combining sources throughout the day can ensure a complete profile.
Associated Nutrients	Often comes with saturated fats and cholesterol (especially red meat).	Typically high in fiber, vitamins, and minerals, and low in saturated fat.
Risk of Chronic Disease	Some links to increased risk of certain cancers and CVD, particularly processed and red meats.	Associated with a reduced risk of chronic diseases.
Examples	Meat, poultry, fish, eggs, and dairy products.	Legumes (beans, lentils), nuts, seeds, grains (quinoa, buckwheat), and soy products.

Conclusion

From the micro-level of cellular enzymes to the macro-level of muscle mass and immune function, the role of protein in health and disease is profound and multifaceted. Adequate intake is necessary for growth, repair, and countless metabolic processes, while both deficiency and excess can lead to serious health issues. A balanced, varied diet that includes high-quality protein from a range of sources is the best approach to leveraging this macronutrient for disease prevention and overall well-being. Ultimately, understanding protein's critical functions empowers individuals to make more informed choices for a healthier life. For more detailed medical information, consult reliable sources such as the MedlinePlus Medical Encyclopedia.

Frequently Asked Questions

A protein deficiency can lead to a number of health issues, including muscle wasting, weakened immunity, edema (fluid buildup), and stunted growth, particularly in children. Severe deficiency can result in conditions like kwashiorkor.

Yes, it is entirely possible to meet all your protein needs with a well-planned plant-based diet. While many plant proteins are incomplete (missing one or more essential amino acids), consuming a variety of protein sources, such as beans, lentils, nuts, and whole grains, throughout the day ensures you get a complete profile.

For most healthy adults, the Recommended Dietary Allowance (RDA) is 0.8 grams of protein per kilogram of body weight. This amount can vary depending on age, activity level, and overall health status. Some athletes or older adults may require more.

Protein helps increase satiety, or the feeling of fullness, which can lead to a reduced overall calorie intake. It also has a higher thermic effect of food compared to carbs and fats, meaning your body burns more energy digesting it.

For individuals with pre-existing kidney disease, a high-protein diet may place extra strain on the kidneys. However, for healthy individuals, evidence suggests that higher protein intake does not typically harm kidney health, but moderation is advised.

Signs can include unexplained fatigue, weakness, muscle loss, brittle hair, skin lesions, and frequent illness due to a weakened immune system.

Protein is a key structural component of bone mass, with over one-third of bone made of protein. Adequate protein intake, along with calcium and vitamin D, supports bone health and has been linked to increased bone mineral density.

No, simply eating more protein does not build muscle on its own. While adequate protein is necessary for muscle repair and growth, it is the stimulation from exercise, particularly strength training, that drives muscle-building.