Why is animal protein so important for your body?

December 22, 2025 •

3 min read

According to a 2024 study, animal-sourced foods are rich sources of protein, essential amino acids, and micronutrients that are often challenging to obtain solely through plant-based options. This is a key reason why is animal protein so important for human health, providing high-quality, bioavailable nutrients vital for various physiological functions.

Quick Summary

Animal protein provides all nine essential amino acids, offering superior bioavailability and nutrient density compared to most plant proteins. These complete proteins support crucial functions like muscle repair, growth, and the maintenance of lean mass, especially vital for active individuals and older adults. It also supplies key micronutrients like vitamin B12 and heme iron, essential for overall health.

Key Points

Complete Amino Acid Profile: Animal proteins are 'complete' proteins, containing all nine essential amino acids needed by the human body in ideal proportions.
Superior Bioavailability: The body absorbs and utilizes animal protein more efficiently than most plant-based proteins.
Supports Muscle Growth and Maintenance: High leucine content in animal protein stimulates muscle protein synthesis, aiding in muscle repair, growth, and combating age-related muscle loss.
Rich in Essential Micronutrients: Animal sources provide critical nutrients like vitamin B12, highly-absorbable heme iron, and zinc, often less available in plant-based diets.
Optimizing Satiety: Animal protein generally promotes a greater feeling of fullness, which can aid in appetite control and weight management.
Aids in Growth and Development: Animal-sourced foods are critical for providing high-quality protein and micronutrients that support infant and child development.

The 'Complete' Amino Acid Profile

Proteins are comprised of building blocks known as amino acids. While the body can synthesize 11 of the 20 required amino acids, nine are 'essential,' meaning they must be obtained through diet. Animal proteins are considered 'complete' because they contain all nine of these essential amino acids in the optimal proportions required for human needs. Many plant-based proteins are 'incomplete,' lacking sufficient amounts of one or more essential amino acids, which necessitates careful planning to achieve a full profile.

Supporting Muscle Growth and Repair

The complete amino acid profile of animal protein is particularly beneficial for muscle growth and repair.

Muscle Protein Synthesis: Animal protein, rich in the essential amino acid leucine, helps trigger muscle protein synthesis (MPS). This process is key for building and repairing muscle tissue. Consuming animal protein post-exercise can maximize muscle recovery.
Mitigating Age-Related Muscle Loss: Adequate protein intake can help combat sarcopenia, the natural decline of muscle mass with age. Studies suggest omnivorous meals may support higher rates of muscle protein synthesis in older adults compared to vegan options. Distributing high-quality protein throughout the day is important for maintaining muscle mass in older populations.

Higher Bioavailability and Nutrient Density

Animal proteins are not only complete but also more bioavailable, meaning the body can absorb and utilize them more efficiently than most plant proteins. This is partly due to factors in plants that can inhibit digestion. Animal sources are often more nutrient-dense, providing crucial vitamins and minerals that are either absent or less bioavailable in plant foods.

Vitamin B12: This vital nutrient is found almost exclusively in animal products, essential for nerve function and red blood cell production. Vegans need fortified foods or supplements for B12.
Heme Iron: Animal products contain heme iron, a form more readily absorbed by the body than the non-heme iron in plants.
Other Essential Micronutrients: Animal-sourced foods are also good sources of nutrients like zinc, selenium, choline, and vitamin D, critical for overall health.

Animal vs. Plant Protein Comparison


Feature	Animal Protein	Plant Protein
Completeness	Contains all nine essential amino acids, making it a 'complete' protein.	Often 'incomplete,' lacking one or more essential amino acids (e.g., legumes lack methionine).
Bioavailability	Generally higher; more easily digested and absorbed by the body.	Generally lower; impacted by antinutrients and fiber.
Nutrient Density	Rich source of high-quality protein and key micronutrients like B12, heme iron, and zinc.	Contains beneficial fiber and phytonutrients, but often lacks B12 and has less bioavailable forms of iron and zinc.
Key Functions	Maximizes muscle protein synthesis, supports growth, and aids tissue repair due to optimal amino acid ratio.	Can support protein needs, especially when different sources are combined, but may be less efficient for rapid muscle repair.
Health Considerations	Certain sources (processed and red meat) linked to health risks, though debate continues. Lean sources (poultry, fish) offer benefits.	Higher intake linked to reduced risk of heart disease and some cancers. Risks associated with relying solely on plant sources for certain nutrients.

A Balanced Perspective on Protein

While animal protein offers significant nutritional advantages, a balanced diet is crucial. Processed red meat has been associated with adverse health effects, though this link is debated. Including a variety of protein sources, both animal and plant-based, is optimal. For those on vegetarian or vegan diets, strategic food combining and supplementation are necessary. Combining legumes with grains, for example, can complete the amino acid profile. Both animal and plant-sourced foods play a complementary role in meeting dietary requirements.

Conclusion

In summary, animal protein is essential for a balanced diet due to its complete amino acid profile, high bioavailability, and concentration of vital micronutrients like vitamin B12 and heme iron. These factors make it uniquely effective for supporting physiological functions, particularly muscle growth and maintenance. While plant proteins have benefits, the ease and completeness of nutrition from animal sources are significant for many nutritional goals. A balanced approach with various high-quality protein sources is the most robust strategy for optimal health. For additional expert resources on protein, visit the Cedars-Sinai blog on the topic(https://www.cedars-sinai.org/blog/best-protein.html).

Frequently Asked Questions

The key difference is the amino acid profile. Animal protein is 'complete,' containing all nine essential amino acids, while most plant proteins are 'incomplete' and must be combined to provide a full profile.

Yes, but it requires careful planning to combine different plant sources (like grains and legumes) throughout the day to ensure you consume all nine essential amino acids.

Animal protein, particularly rich in the essential amino acid leucine, is a more potent stimulator of muscle protein synthesis compared to most plant proteins. However, adequate muscle building can still be achieved with a well-planned, high-protein plant-based diet.

Animal protein sources are excellent providers of vitamin B12 and highly absorbable heme iron, both of which are scarce in plant foods.

While some observational studies have linked processed red meat with increased health risks, more robust research indicates this association is complex and often influenced by other lifestyle factors. Lean animal protein sources like poultry and fish have not been linked to these negative outcomes.

Bioavailability measures how easily the body can digest and absorb nutrients. Animal protein has higher bioavailability, meaning your body gets more nutritional value from a smaller amount compared to many plant sources.

Yes, a balanced diet that includes both animal and plant proteins is often recommended to benefit from the unique strengths of each source, ensuring a complete and nutrient-dense intake.