Which of the following is a high-quality protein?

January 9, 2026 •

4 min read

According to the Food and Agriculture Organization of the United Nations, a high-quality protein is measured by its amino acid profile and digestibility. In simple terms, a high-quality protein, also known as a complete protein, contains all nine essential amino acids that your body cannot produce on its own. Making informed choices about protein can significantly impact your health, from muscle repair to immune function.

Quick Summary

This article explores the definition and importance of high-quality protein, outlining the factors that determine protein quality. It compares animal and plant-based sources, lists examples of complete proteins, and provides guidance for building a balanced, protein-rich diet.

Key Points

Essential Amino Acids: High-quality protein contains all nine essential amino acids that the body cannot produce on its own.
Complete vs. Incomplete: Animal products (meat, eggs, dairy) are typically complete proteins, while most plant foods are incomplete unless combined effectively.
Protein Quality Measurement: The PDCAAS and DIAAS are scientific methods used to evaluate protein quality based on amino acid profile and digestibility.
Key Plant-Based Options: Soy products, quinoa, and buckwheat are notable plant-based sources of complete protein.
Protein Combining: Vegetarians and vegans can meet their complete protein needs by combining complementary foods, such as rice and beans.
Health Benefits: A diet rich in high-quality protein supports muscle repair, satiety, and overall metabolism.

Understanding High-Quality Protein

High-quality protein is defined primarily by two characteristics: its amino acid profile and its digestibility. The body needs 20 different amino acids to function properly, nine of which are considered 'essential' because they cannot be synthesized by the body and must be obtained through food. A high-quality or 'complete' protein source contains all nine of these essential amino acids in sufficient quantities.

The measurement of protein quality has evolved over time. The Protein Digestibility-Corrected Amino Acid Score (PDCAAS), for instance, has been a standard method for decades, though the Food and Agriculture Organization (FAO) has proposed a newer method, the Digestible Indispensable Amino Acid Score (DIAAS). A higher score on these scales indicates better protein quality, meaning the protein provides all essential amino acids and is more easily digested and absorbed by the body.

The Importance of a Complete Amino Acid Profile

Proteins serve as the fundamental building blocks for all cells, tissues, and organs. A complete profile of essential amino acids is critical for processes like muscle growth and repair, immune function, and the synthesis of enzymes and hormones. If even one essential amino acid is missing or insufficient, the body's ability to synthesize new proteins can be compromised. This is particularly important for athletes, older adults, and those with specific health goals, as adequate high-quality protein intake can help preserve muscle mass, aid recovery, and increase satiety.

Comparing Animal and Plant-Based Protein Sources

Animal-based products are often considered classic examples of high-quality, complete proteins. These sources naturally contain all essential amino acids in the proportions the human body needs. However, a growing number of plant-based foods have also been identified as complete proteins, and vegetarians and vegans can achieve a complete amino acid profile by combining different plant sources throughout the day.

Animal Protein Sources:
- Meat (beef, chicken, pork)
- Poultry (turkey, duck)
- Fish and seafood (salmon, tuna)
- Eggs
- Dairy products (milk, cheese, Greek yogurt)
Plant-Based Protein Sources (Complete and Incomplete):
- Complete: Soy products (tofu, tempeh, edamame), quinoa, buckwheat, and hemp seeds.
- Complementary Combinations: Combining legumes (beans, lentils) with grains (rice, whole wheat bread) can create a complete protein meal.

High-Quality Protein Examples and Comparison

The quality of protein is often assessed using objective measures like the PDCAAS. Below is a comparison of various protein sources based on this scientific metric. A score of 1.0 is the highest possible, indicating the protein provides 100% of the essential amino acids required for humans after digestion.


Protein Source	Typical PDCAAS Score	Key Characteristics
Eggs	1.00	Often used as the benchmark for protein quality; highly digestible.
Whey Protein Isolate	1.00	A milk protein rapidly digested and utilized by the body, popular in fitness.
Casein	1.00	Another milk protein that is digested slowly, providing a sustained release of amino acids.
Soy Protein Isolate	1.00	A high-quality, plant-based complete protein, making it an excellent alternative.
Beef	0.92	A complete animal protein, though it scores slightly lower due to digestibility factors.
Pea Protein Concentrate	0.89	A plant-based source that benefits from being combined with other proteins, like rice, to balance its amino acid profile.
Black Beans	0.75	An incomplete plant protein that becomes complete when combined with grains like rice.
Wheat Gluten	0.25	A low-quality protein on its own, with a limited amino acid profile.

How to Build a High-Quality Protein Diet

Creating a diet rich in high-quality protein doesn't mean you must eat only animal products. A balanced approach that incorporates a variety of both animal and plant sources is beneficial for overall health. For those on a vegetarian or vegan diet, combining different plant foods throughout the day is a straightforward strategy to ensure you meet all your essential amino acid needs. For example, a meal of rice and beans, hummus with pita bread, or a stir-fry with tofu and vegetables can provide a complete protein profile.

To optimize your protein intake, consider spacing it out throughout your day. For instance, incorporating protein into each meal and snack can help maintain a positive protein balance, supporting muscle repair and overall metabolic function. This strategy is particularly effective for those looking to manage weight, as protein increases satiety and helps curb hunger.

Conclusion: Making the Best Protein Choices

Determining which of the following is a high-quality protein depends on its amino acid content and digestibility. Animal sources like meat, eggs, and dairy are consistently high-quality, but several plant-based options like soy and quinoa also fit this description. For those relying on a plant-based diet, protein combining is a simple and effective method to ensure all essential amino acids are consumed. The ultimate goal is to incorporate a variety of protein sources into your daily diet to support your health, fitness, and nutritional needs, regardless of your dietary preferences.

Prioritize complete proteins: Focus on sources like eggs, dairy, soy, and quinoa to ensure you are receiving all essential amino acids.
Practice protein combining: If consuming incomplete plant proteins, pair them with complementary foods to create a complete amino acid profile.
Diversify your sources: A variety of protein sources provides a broader range of nutrients beyond just amino acids.
Consider digestibility: High-quality proteins are also easily digested and absorbed by the body, which can be measured using scores like PDCAAS.

Frequently Asked Questions

The nine essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. They must be obtained through the diet because the human body cannot produce them.

Most animal proteins, such as those from meat, fish, eggs, and dairy, are considered high-quality or complete because they contain all nine essential amino acids. Beef, eggs, and dairy often have high PDCAAS scores, reflecting their quality.

Yes, it is possible to get high-quality protein from plant-based foods. Some plant foods, like soy (tofu, tempeh), quinoa, and buckwheat, are naturally complete proteins. By combining different incomplete plant proteins, you can also create a complete amino acid profile.

The main difference lies in the amino acid profile and digestibility. High-quality protein provides all essential amino acids in the right proportions and is easily absorbed, whereas low-quality protein lacks one or more essential amino acids and may be less digestible.

It is not necessary to consume a complete protein at every single meal. The body can draw from a stored pool of amino acids, so ensuring you get a balanced intake of all essential amino acids throughout the day is sufficient.

Cooking generally does not significantly harm the amino acid profile of a protein, but certain processing methods can affect its digestibility. The quality is primarily determined by its natural composition.

Protein is vital for numerous bodily functions. It helps build and repair tissues, produces enzymes and hormones, and supports immune function. It is a critical component of every cell in the body.