Is tofu a low biological value protein?

December 1, 2025 •

4 min read

According to older and less accurate protein rating methods, the Biological Value (BV) of tofu has been cited as being lower than animal-based proteins. However, modern nutritional science and more comprehensive metrics reveal that the idea that tofu is a low biological value protein is largely outdated, and its protein is, in fact, high-quality and highly digestible.

Quick Summary

This article examines the quality of tofu's protein by explaining different nutritional metrics like Biological Value (BV) and Protein Digestibility Corrected Amino Acid Score (PDCAAS). It reveals why tofu is considered a high-quality, complete protein based on modern scientific standards, despite older, incomplete analyses.

Key Points

BV is Outdated: The claim that tofu is a low biological value protein relies on an older metric (BV); modern science uses more accurate measures like PDCAAS.
High-Quality Soy Protein: Soy protein, the base for tofu, is rated as a high-quality protein comparable to animal sources based on modern PDCAAS scores.
Complete Amino Acid Profile: Tofu is one of the few plant-based foods that offers all nine essential amino acids, making it a complete protein.
Highly Digestible: The processing of soybeans into tofu significantly increases its digestibility to over 90%, meaning the body can readily use its protein.
Rich in Nutrients: Tofu is more than just protein; it's also a good source of heart-healthy polyunsaturated fats, minerals like calcium and iron, and beneficial isoflavones.
Firmness Affects Content: The density of tofu varies by firmness, with extra-firm varieties containing a higher concentration of protein and nutrients per serving.
Heart-Healthy Choice: As a cholesterol-free, low-saturated-fat option, incorporating tofu can support cardiovascular health.

Understanding Protein Quality Metrics

To determine if a protein source is "high quality," nutritionists use several metrics that evaluate its amino acid profile and digestibility. Historically, the Biological Value (BV) was a popular method, but its flaws have led to more modern, accurate approaches.

The Older Biological Value (BV) Score

The Biological Value is a measure that estimates the percentage of absorbed protein from a food that is incorporated into proteins within the body. It relies on measuring nitrogen retention and is an outdated method for several reasons. For instance, early BV testing used young rats with different protein needs than humans, leading to skewed results, especially concerning sulfur-containing amino acids. This metric alone does not provide a complete picture of a food's nutritional value or bioavailability.

The Modern Standard: PDCAAS and DIAAS

Recognizing the limitations of older tests, the World Health Organization (WHO) and Food and Agriculture Organization (FAO) adopted the Protein Digestibility Corrected Amino Acid Score (PDCAAS) as the preferred method for assessing protein quality. More recently, the Digestible Indispensable Amino Acid Score (DIAAS) has also been developed. These scores consider two crucial factors:

The food's essential amino acid composition.
The digestibility of the protein.

Proteins with a PDCAAS of 1.0 are considered complete and high-quality, comparable to casein and egg white. This is where the narrative about tofu's protein quality is often clarified.

The Protein Quality of Soy and Tofu

The claim that tofu is a low biological value protein stems from focusing solely on its older BV score of 64. However, this metric is less meaningful when considering the food's overall processing and digestibility, and the modern PDCAAS provides a clearer answer.

High Protein Score and Digestibility

According to modern PDCAAS standards, soy protein is considered to have a quality equivalent to many animal proteins. Soy protein isolate, a processed form derived from soybeans, often receives a PDCAAS of 0.92-0.99, putting it on par with beef and eggs. Crucially, the processing of soybeans into tofu, which includes soaking and boiling, significantly increases its digestibility from about 65% for raw beans to over 90%.

Tofu is a Complete Protein

One of the most important takeaways is that tofu contains all nine essential amino acids your body needs but cannot produce on its own. This status as a complete protein makes it an excellent and versatile source for vegetarians and vegans who may be concerned about their amino acid intake.

Processing and Density Affect Tofu's Nutritional Profile

The firmness of tofu is directly related to its protein and nutrient density. The process of pressing soy curds to remove water results in firmer blocks with a higher concentration of nutrients per serving.

Silken Tofu: Unpressed, higher water content, lower protein density (~4-6g per 100g).
Firm Tofu: Pressed to remove water, moderate protein density (~10-12g per 100g).
Extra-Firm Tofu: Heavily pressed, highest protein density (~12-15g per 100g).

Comparison of Protein Quality Metrics


Protein Source	Biological Value (BV)	PDCAAS Score	Notes
Egg White	~94	1.00 (Standard)	Often considered the gold standard for protein quality.
Beef	~74	0.92	High quality, but higher in saturated fat.
Soy Protein Isolate	74	0.92–0.99	Highly refined soy protein, very high quality.
Whole Soy Bean	96	0.96	The raw bean, which has different properties after processing.
Tofu (Soy Curd)	64	N/A (High)	The BV is lower, but high digestibility and amino acid profile make it high quality.
Whole Wheat	64	N/A	Incomplete protein, needs combining with other sources.

Health Benefits Beyond Protein Quality

Beyond its high-quality protein, tofu offers numerous other health benefits, making it a valuable addition to a balanced diet. It is a complete food, not just an isolated protein source.

Cholesterol-Free: Unlike animal proteins, tofu contains no cholesterol and is low in saturated fat, contributing to better heart health.
Heart Health: Studies suggest that regular soy protein consumption may lower LDL (“bad”) cholesterol levels, which can reduce the risk of heart disease.
Rich in Minerals: Tofu is an excellent source of calcium, iron, magnesium, and other minerals, which support bone health and prevent osteoporosis.
Isoflavones: Soy contains isoflavones, plant compounds with antioxidant properties that may help reduce the risk of certain cancers, including breast and prostate cancers.
Weight Management: The high protein content and low calories can promote feelings of fullness, aiding in weight management.

Conclusion

The perception of tofu being a low biological value protein is misleading and based on outdated measurement methods. While its raw soybean source has an impressive BV, the processed form, tofu, is even more digestible due to heat and processing. By modern, more accurate metrics like PDCAAS, soy protein rivals animal protein in quality. As a complete protein source rich in essential amino acids, minerals, and heart-healthy fats, tofu offers significant nutritional value, especially when integrated into a varied, plant-forward diet.

For more detailed information on protein quality assessment and soy's role in nutrition, consult scientific literature like those found on the National Institutes of Health website.

Frequently Asked Questions

Yes, tofu is a complete protein, meaning it contains all nine of the essential amino acids that the human body needs. This makes it an excellent plant-based alternative to animal proteins.

Older BV rating scales place tofu's score at 64. However, this metric is now considered less reliable than modern standards like the Protein Digestibility Corrected Amino Acid Score (PDCAAS) and is not the best indicator of overall protein quality.

Yes. The processing of soybeans into tofu, which involves heating and curdling, significantly increases the digestibility of the protein to over 90%. This ensures that a high percentage of the protein is absorbed and utilized by the body.

Using modern metrics like PDCAAS, soy protein is rated as high-quality, often scoring comparably to animal proteins like beef and eggs. While some older metrics show a difference, tofu offers a comparable protein profile without the saturated fat and cholesterol found in many animal products.

Processing significantly improves the digestibility of soy protein. Heat treatment during tofu production helps to denature protein-inhibiting compounds present in raw soybeans, making the protein more accessible for human digestion.

Yes. The protein content varies depending on the firmness. Extra-firm tofu, which has been pressed to remove more water, has a higher protein density per serving than soft or silken tofu.

The BV metric is largely considered outdated for human nutrition due to methodological flaws. Modern standards like PDCAAS and DIAAS are more accurate as they account for both the amino acid profile and the protein's digestibility.

Tofu is a nutrient-dense food rich in minerals like calcium, iron, magnesium, and manganese. It is also an excellent source of isoflavones and heart-healthy polyunsaturated fats, with no cholesterol.