What is the BV of a protein? Understanding Biological Value in Nutrition

October 4, 2025 •

5 min read

Not all protein sources are created equal in the body; a protein's quality is a key factor in its effectiveness. The biological value (BV) of a protein is a measure of how efficiently the body absorbs and utilizes a protein for synthesis and maintenance. This metric helps illustrate why the amino acid composition of your food is so vital for your nutritional goals.

Quick Summary

This article explains what biological value (BV) is, its significance in nutrition, and how it is measured, highlighting its strengths and weaknesses compared to modern protein scoring methods like PDCAAS and DIAAS.

Key Points

BV Definition: Biological Value measures how efficiently the body uses absorbed protein for tissue synthesis.
Essential Amino Acids: High BV is associated with a protein source containing all essential amino acids in sufficient amounts.
BV Limitations: The metric has limitations, as it doesn't account for digestibility and can be influenced by other dietary factors.
Modern Alternatives: More advanced methods like PDCAAS and DIAAS are now used to evaluate protein quality for humans.
Protein Complementation: The BV concept underpins the strategy of combining different incomplete protein sources (e.g., rice and beans) to improve overall protein quality.
Diverse Diet is Key: A balanced diet with various protein sources naturally ensures a complete amino acid profile, mitigating the need to strictly follow BV scores.

What is the BV of a Protein?

The term biological value (BV) refers to the proportion of protein from a food source that is absorbed and incorporated into the body's own proteins. It essentially captures how well a protein's amino acid profile matches the body's needs for synthesis, growth, and maintenance. A high BV indicates that a large percentage of the protein absorbed is retained and used, while a low BV suggests a less efficient utilization. This metric has historically been a significant tool in nutritional science for evaluating the quality of different dietary proteins.

Proteins with a high BV, often called 'complete proteins,' contain all nine essential amino acids (EAAs) in amounts that are well-suited for human requirements. Essential amino acids are those the body cannot produce on its own and must be obtained through diet. If a protein source lacks or has a very low amount of just one EAA, that amino acid becomes a 'limiting amino acid,' and the overall BV is reduced.

How BV is Calculated

The biological value is determined through a nitrogen balance study, which measures the amount of nitrogen retained in the body relative to the amount absorbed. Since protein is the primary dietary source of nitrogen, this provides an indirect measure of protein utilization. The classic formula is as follows:

$BV = (Nitrogen Retained / Nitrogen Absorbed) \times 100$

This method requires controlled, and often artificial, dietary conditions where the subject consumes only the protein of interest. A BV score can range from 0 to 100, with some relative scores, like those for whey protein, exceeding 100 when compared against a reference standard like egg protein.

Factors Affecting a Protein's BV

Several factors can influence a protein's biological value:

Amino Acid Composition: This is the most crucial factor. The presence and proportion of essential amino acids are the primary determinants of a protein's BV. A protein with an EAA profile similar to human tissue has a high BV.
Food Preparation: The way food is cooked and processed can impact the availability of amino acids. For example, excessive heat can sometimes damage or denature proteins, potentially reducing their BV.
Combined Proteins: Consuming a variety of proteins, especially combining plant-based proteins, can significantly increase the overall BV of a meal. A concept known as 'protein complementing' or 'mutual supplementation' involves pairing two or more incomplete proteins to create a complete amino acid profile. For instance, beans and rice, when eaten together, form a high-quality protein blend.
Digestibility: While BV strictly measures the utilization of absorbed protein, a protein's digestibility also affects overall quality. The BV method, however, does not fully account for differences in digestibility between different food sources.

BV vs. Modern Protein Quality Metrics

While BV was a foundational concept, modern nutrition science uses more advanced metrics that address its limitations. The most notable alternatives are the Protein Digestibility Corrected Amino Acid Score (PDCAAS) and the Digestible Indispensable Amino Acid Score (DIAAS).

Comparison of Protein Quality Metrics


Feature	Biological Value (BV)	PDCAAS	DIAAS
Focus	Efficiency of absorbed protein utilization	Amino acid profile and fecal digestibility	Amino acid profile and ileal digestibility
Data Source	Nitrogen balance studies, often on animals (rats)	Human amino acid requirements (2-5 year olds)	Human amino acid requirements, ileal digestibility
Limitations	Ignores digestibility; relies on nitrogen balance; often animal data	"Truncates" score at 1.0; fecal vs. ileal digestibility concerns	Still debated and newer, but more precise than PDCAAS
Maximum Score	Can exceed 100 (relative scale)	Capped at 1.0	No cap, allows for higher values

High BV Protein Sources

Generally, animal-based proteins have higher biological values because their amino acid profiles are closer to those of human tissue. However, many plant-based proteins can be combined to achieve a high BV.

High BV Sources (Animal)
- Egg (often used as the gold standard with a BV of 100 on the relative scale)
- Whey Protein (can have relative scores over 100)
- Milk and Dairy Products
- Meat (Beef, Chicken, Fish)
High BV Sources (Combined Plant)
- Rice and Beans: A classic example of protein complementing, where the amino acid deficiencies of one are covered by the other.
- Soy Protein: An exception among plants, it is a complete protein with a relatively high BV.
- Quinoa: A complete protein often used as a plant-based alternative to animal sources.

Conclusion: The Modern View of BV

Although newer, more accurate methods like DIAAS have largely replaced BV in regulatory settings, understanding what is the BV of a protein provides valuable insight into protein quality. It highlights the fundamental importance of consuming proteins with a balanced profile of essential amino acids for efficient bodily use. While a high BV is a positive indicator, nutrition is complex, and a well-balanced diet containing a variety of protein sources is often the best approach to ensure all amino acid needs are met. The knowledge of protein complementing, a concept rooted in BV principles, remains highly relevant for individuals, especially those following plant-based diets, to maximize their nutritional intake.

How to Maximize Your Protein Intake

Diversify your protein sources: Don't rely on just one type of protein. Combining animal and plant proteins, or different plant proteins, ensures a complete amino acid intake.
Incorporate complementary proteins: Pair legumes (like beans) with grains (like rice) in the same meal to boost the overall biological value.
Consider supplements wisely: Whey protein, with its very high BV, can be an efficient way to increase protein intake, particularly for athletes, but isn't always necessary for most people.
Be mindful of cooking: While cooking is necessary for safety, excessive heat can damage protein structures, but proper preparation often improves digestibility and absorption.
Focus on overall diet: BV is only one piece of the puzzle. Factors like total calorie intake, micronutrients, and fiber also play a critical role in protein utilization and overall health.

A Final Word on Biological Value

The biological value concept, despite its limitations and the advent of more sophisticated measurement tools, remains a useful educational foundation for understanding protein quality. It teaches us that the specific building blocks (amino acids) are just as important as the quantity of protein consumed. By focusing on dietary diversity, complementing protein sources, and considering overall nutritional needs, individuals can move beyond the single-number rating of BV to build a truly effective and balanced diet.

Frequently Asked Questions

A high BV protein is one that is efficiently absorbed and retained by the body due to its complete and balanced amino acid profile. Animal proteins like eggs, whey, and meat typically have high BV scores, as do some plant sources like soy.

Generally, single plant protein sources have a lower BV than animal proteins because they are often missing or low in one or more essential amino acids. However, by combining different plant proteins, like rice and beans, a higher overall BV can be achieved.

Yes, you can increase the BV of a meal by practicing protein complementation. This involves combining different protein sources, such as grains and legumes, so that the amino acids lacking in one are provided by the other, creating a more complete protein profile.

Whole egg protein is frequently used as a standard for BV because its amino acid composition is very close to the ideal needed by the human body, giving it a high score (100 on the relative scale). It is often used as a reference point to compare other proteins.

PDCAAS (Protein Digestibility Corrected Amino Acid Score) and DIAAS (Digestible Indispensable Amino Acid Score) are more modern and accurate protein quality metrics. Unlike BV, which only considers absorbed protein, both PDCAAS and DIAAS factor in a protein's digestibility in humans, providing a more relevant measure for dietary planning.

For most individuals who consume a varied diet with a mix of different protein sources, focusing on a single food's BV is less critical. The combined effect of eating multiple proteins will likely provide all the necessary essential amino acids over the course of a day.

Cooking can affect a protein's BV by altering its structure and bioavailability. Proper cooking can increase digestibility, but overcooking or using certain high-heat methods can potentially damage some amino acids and reduce the protein's overall quality.