What is the Biological Value of Protein? A Detailed Nutrition Guide

January 6, 2026 •

5 min read

The biological value (BV) is a measure of how efficiently the body uses protein from food for growth and tissue repair. It quantifies the proportion of absorbed protein that becomes incorporated into the body's own proteins, offering a key metric for determining protein quality in different food sources.

Quick Summary

The biological value of a protein measures how efficiently the body utilizes it based on nitrogen retention. It is influenced by essential amino acid content and varies between food sources, with animal proteins generally scoring higher than plant-based ones.

Key Points

Definition: Biological Value (BV) measures how efficiently your body utilizes absorbed protein for tissue synthesis and repair.
Amino Acids: BV is primarily determined by a protein source's content of essential amino acids, which the body cannot produce itself.
Comparison with Newer Metrics: Newer scoring systems like PDCAAS and DIAAS offer more advanced evaluations by incorporating factors like digestibility, often preferred for accuracy over BV.
Food Synergy: Combining incomplete plant proteins, like rice and beans, can create a complete amino acid profile and increase the meal's overall BV.
Dietary Factors: Factors such as cooking methods, total energy intake, and an individual's health status can influence the actual BV of a protein source.
High-Quality Sources: High BV foods, such as eggs, whey, and milk, contain all nine essential amino acids in sufficient quantities.

Understanding the Biological Value (BV)

Biological Value (BV) is a metric used to assess the quality of a protein source by measuring the proportion of absorbed protein that is retained by the body for synthesis into its own proteins. A higher BV indicates that a greater percentage of the protein absorbed from a food source is successfully utilized, leading to more efficient tissue formation and repair. The BV concept is based on nitrogen balance studies, as proteins are the body's primary source of nitrogen. The amount of nitrogen a person ingests is measured against the amount they excrete, with the remainder assumed to be incorporated into the body.

Essential Amino Acids: The Foundation of BV

At the core of BV is the concept of essential amino acids (EAAs). These are the nine amino acids that the human body cannot produce on its own and must be obtained through diet. For the body to build new protein, all nine EAAs must be present in sufficient quantities. A protein source is considered 'complete' if it contains all nine EAAs, and 'incomplete' if it lacks or is deficient in one or more. A protein's BV is largely determined by its essential amino acid profile. The EAA in the lowest quantity, relative to the body's needs, is called the 'limiting amino acid' and acts as a bottleneck for protein synthesis.

How Biological Value is Calculated

The calculation for BV is based on a specific formula that accounts for nitrogen intake and excretion. While direct measurement is complex, it is derived from the nitrogen absorbed and the nitrogen retained by the body over a test period.

$BV = (Nitrogen~Retained \div Nitrogen~Absorbed) \times 100$

This formula reflects how efficiently the absorbed protein nitrogen is converted into bodily tissue. Egg protein has historically been used as a benchmark, given a BV of 100, which has led to some proteins scoring over 100 when tested comparatively, such as whey protein.

Comparing Protein Quality Metrics: BV, PDCAAS, and DIAAS

While BV has been a standard measure, newer, more advanced methods have been developed to provide a more accurate picture of protein quality.

BV vs. PDCAAS vs. DIAAS Comparison


Feature	Biological Value (BV)	Protein Digestibility Corrected Amino Acid Score (PDCAAS)	Digestible Indispensable Amino Acid Score (DIAAS)
Primary Basis	Nitrogen retention from absorbed protein.	Amino acid score corrected for fecal crude protein digestibility.	Ileal amino acid digestibility based on reference patterns.
Key Focus	Measures protein usability once absorbed.	Measures amino acid content and digestibility for human nutrition.	Offers a more accurate measure of individual amino acid absorption.
Truncation	No maximum limit; can exceed 100.	Scores are truncated at 1.00 (or 100%).	Scores are not truncated, allowing for better differentiation.
Digestibility Measure	Does not account for digestibility.	Uses standardized fecal crude protein digestibility.	Uses standardized ileal (end of small intestine) amino acid digestibility.
Animal Models	Often measured in rats, results can differ in humans.	Typically uses rats for digestibility data.	Can utilize humans, growing pigs, or rats, with human data preferred.

Factors Influencing Protein's Biological Value

The BV of a protein isn't fixed; several factors can affect its final score and how your body utilizes it. These include:

Amino Acid Composition: The single most important factor. If a protein is missing or low in one or more essential amino acids, its BV will be lower.
Food Preparation: Cooking methods can alter a protein's structure and affect the availability of amino acids. Gentle heating can sometimes increase bioavailability (e.g., eggs), while high heat can cause damage and reduce BV.
Complementary Proteins: Combining different incomplete protein sources can create a complete amino acid profile, effectively increasing the BV of the meal. For example, pairing rice (low in lysine) with beans (low in methionine) forms a more complete protein.
Energy Intake: If a person's total calorie intake is insufficient, the body may burn protein for energy instead of using it for tissue synthesis, reducing its overall utilization and BV.
Individual Factors: A person's age, health status, and metabolic rate can all influence how efficiently they utilize protein. For example, athletes or individuals recovering from injury may have higher protein needs.

High Biological Value Foods

Animal proteins are typically considered high BV because they contain all nine essential amino acids in proportions similar to the human body's needs. However, certain plant sources and clever combinations can also achieve a high BV. Here is a list of some common foods and their relative BV values (using egg as the benchmark of 100):

Whey Protein Concentrate: 104
Whole Egg: 100
Cow's Milk: 91
Beef: 80
Casein: 77
Soy Protein: 74
Rice and Beans (combined): 101
Potatoes and Eggs (combined): 136

How to Maximize Your Protein Intake

To ensure your body makes the most of the protein you consume, consider these strategies:

Focus on complete protein sources: Prioritize foods like eggs, dairy, meat, and soy that contain all essential amino acids.
Use complementary proteins: Mix different plant-based foods to create a complete amino acid profile. Examples include hummus with pita bread, or lentils with rice.
Distribute protein throughout the day: Spreading your protein intake across multiple meals can optimize utilization and reduce amino acid oxidation.
Consume adequate energy: Ensure you are meeting your daily calorie needs so your body can use protein for its primary functions rather than as an energy source.
Consider protein timing: For those engaged in resistance training, consuming high-quality protein both before and after a workout can enhance muscle protein synthesis.

Conclusion

Understanding what the biological value of protein represents is crucial for optimizing nutritional intake. While BV measures the body's efficiency in using absorbed protein, modern metrics like DIAAS provide a more refined assessment of protein quality, factoring in crucial elements like digestibility. By focusing on a combination of high-BV food sources, complementary plant proteins, and balanced energy intake, you can effectively enhance your body's utilization of this vital macronutrient. This approach ensures you meet your needs for tissue synthesis and repair, supporting overall health and wellness. For more details on the evolution of protein quality assessment, refer to the Digestible indispensable amino acid score (DIAAS): 10 years on review.

Frequently Asked Questions

The formula is calculated as the ratio of nitrogen retained by the body to the nitrogen absorbed from food, multiplied by 100. It measures the percentage of absorbed protein utilized by the body.

BV was traditionally benchmarked against egg protein, which was assigned a value of 100. As such, some proteins that contain an amino acid profile more aligned with human needs than egg protein, like whey, can achieve a relative BV score higher than 100.

Animal proteins generally have a higher BV because they are 'complete' proteins, containing all essential amino acids in optimal proportions. Many plant proteins are 'incomplete,' but can be combined to form a complete protein, thereby increasing the meal's BV.

While BV is a foundational concept, it is not considered the best modern metric. Newer systems like PDCAAS and, more recently, DIAAS, are often preferred because they account for digestibility and the availability of individual amino acids more accurately.

Yes, cooking can affect BV. In some cases, like cooking eggs, heating can increase the bioavailability and BV of the protein. However, excessive heat can denature proteins and damage amino acids, potentially lowering the BV.

The limiting amino acid is the essential amino acid present in the smallest quantity relative to the body's needs within a particular protein source. It is the factor that limits the body's ability to synthesize new protein.

By strategically combining different plant-based protein sources, you can ensure all essential amino acids are present. Classic combinations include rice and beans, hummus with pita bread, or lentils with nuts and seeds.