Understanding a Nutrition Diet: Which of the following is considered a high quality protein?

October 15, 2025 •

3 min read

Not all dietary protein is created equal; its quality is determined by its amino acid composition and digestibility. Understanding which of the following is considered a high quality protein? is crucial for building and repairing tissues, supporting metabolic functions, and optimizing overall health.

Quick Summary

This guide explains what defines a high-quality protein, detailing the nine essential amino acids it must contain. It contrasts complete and incomplete protein sources, examines different scoring methods, and provides a list of top animal and plant-based examples to maximize your nutrient intake.

Key Points

Complete Amino Acid Profile: A high-quality protein contains all nine essential amino acids, which the body cannot produce on its own.
High Digestibility: The protein must be efficiently broken down and absorbed by the body to be considered high quality.
Top Animal Sources: Eggs, milk, and lean meats are prime examples of high-quality animal proteins due to their complete amino acid content and high digestibility.
Key Plant Sources: Soy (tofu, tempeh) and quinoa are two of the few plant-based foods that are naturally complete proteins.
The "Protein Package": When choosing protein, also consider the accompanying nutrients like fats and fiber; for instance, opting for lean meat over processed versions is healthier.
Complementary Proteins: Vegetarians can achieve a complete amino acid profile by combining different incomplete plant proteins, like rice and beans, throughout the day.

What Defines a High-Quality Protein?

Protein quality is evaluated based on two primary factors: its amino acid profile and its digestibility. Amino acids are the building blocks of protein, and our bodies need 20 different kinds to function properly. Nine of these are considered "essential" because the body cannot produce them on its own and must obtain them from food. A high-quality protein is defined as one that contains all nine of these essential amino acids in adequate proportions.

The Role of Essential Amino Acids

The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Each plays a unique role in the body, from promoting muscle protein synthesis to supporting immune function and hormone production. The presence of all nine in sufficient amounts is what makes a protein source "complete" and, therefore, high quality. Animal-based proteins, such as meat, fish, eggs, and dairy, are naturally complete proteins and generally have excellent amino acid scores.

Digestibility and Bioavailability

Beyond the amino acid profile, a protein's digestibility and bioavailability are key. Digestibility refers to how easily the body can break down and absorb the protein's amino acids. Animal proteins typically have a higher digestibility rate than most plant-based proteins due to differences in their cellular structure and the presence of anti-nutritional factors in plants. This is one reason why official protein quality scores, like the Protein Digestibility Corrected Amino Acid Score (PDCAAS), include a digestibility correction. The newer Digestible Indispensable Amino Acid Score (DIAAS) takes this a step further by measuring amino acid digestibility at the end of the small intestine for a more accurate assessment.

High-Quality Protein Sources

Both animal and plant-based diets can provide high-quality protein, though some sources require more strategic planning than others. A varied diet is the best way to ensure you are getting all the essential amino acids you need.

Animal-Based High-Quality Proteins:

Eggs: Often considered the gold standard, eggs have a perfect amino acid score and high digestibility.
Milk and Dairy: Products like milk, yogurt (especially Greek yogurt), and cheese contain high-quality casein and whey proteins.
Lean Meats: Chicken breast, lean beef, and turkey provide all essential amino acids and are rich in other nutrients like iron and zinc.
Fish and Seafood: Salmon, tuna, and other fish offer complete protein along with heart-healthy omega-3 fatty acids.

Plant-Based High-Quality Proteins:

Soy Products: Tofu, tempeh, and edamame are among the few plant-based foods that are complete proteins.
Quinoa: This gluten-free seed is a complete protein, containing all nine essential amino acids.
Hemp and Chia Seeds: Both are complete protein sources, providing a good ratio of all essential amino acids.

For those following a plant-based diet, combining different incomplete protein sources throughout the day, such as rice and beans or hummus and pita, can create a complete protein meal.

Comparing Common Protein Sources


Protein Source	Type	Complete Protein?	Key Amino Acids	Digestibility (Example PDCAAS)	Key Nutritional Benefit
Eggs	Animal	Yes	All 9 Essential AAs	1.00	Highly bioavailable; rich in vitamins and minerals.
Whey Protein	Animal (Dairy)	Yes	High in BCAAs (Leucine)	1.00	Rapid absorption; ideal for muscle recovery.
Soy Protein Isolate	Plant	Yes	All 9 Essential AAs	1.00 (varies by processing)	Versatile plant-based option; good for vegetarians.
Lean Beef	Animal	Yes	High in BCAAs, Iron, Zinc	0.92	Excellent source of iron and zinc; supports muscle growth.
Quinoa	Plant	Yes	All 9 Essential AAs	Good, but often lower than animal sources	Complete plant protein; high in fiber and minerals.
Lentils	Plant	No (Limited Methionine)	High in Lysine	0.52	High in fiber, folate, and iron; great when combined with grains.

Conclusion

When evaluating a high-quality protein, it's essential to consider its complete amino acid profile and high digestibility. Animal products like eggs, dairy, lean meats, and fish are classic examples, providing all nine essential amino acids in a readily absorbable form. For plant-based diets, sources like soy, quinoa, and hemp seeds are excellent options, and combining various plant proteins throughout the day can ensure all essential amino acids are consumed. Ultimately, a balanced and varied approach to your diet, focusing on whole food sources, is the most reliable way to meet your body's protein needs. For more comprehensive information, consult resources like the Harvard T.H. Chan School of Public Health on protein sources.

Frequently Asked Questions

The primary factor is its amino acid profile. A high-quality protein, also known as a complete protein, must contain all nine essential amino acids that the body cannot produce on its own.

Most animal-based proteins, including eggs, dairy, meat, and fish, are high-quality because they contain all essential amino acids in a highly digestible form. However, some, like collagen, are exceptions.

Vegetarians and vegans can get high-quality protein by consuming complete plant proteins like soy and quinoa, or by combining various incomplete plant proteins throughout the day, such as pairing grains with legumes.

Complementary proteins are two or more incomplete protein sources that, when eaten together, provide all nine essential amino acids. An example is rice and beans.

The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is a method for evaluating protein quality that considers both the amino acid profile and digestibility. A score of 1.0 is the highest possible.

Proper cooking generally does not significantly diminish protein quality. However, excessive heating or certain processing methods can affect digestibility and amino acid availability.

No, it is not necessary to consume a complete protein at every single meal. As long as you consume a variety of protein sources throughout the day, your body can pool amino acids to form complete proteins.