2 of 3: Toor Dal vs Mutton – Which is Better? What Do PDCAAS and DIASS Tests Tell Us

Disclaimer – Can one bowl of dal really replace a serving of mutton? This is an evidence-based nutritional comparison for Indians. Your dietary choices are truly your soverign, solemn decision – this write up is only an attempt at what science, hopefully conclusively,  says about Protein from Plant v/s Protein from Animal Source. To our knowledge this is the most comprehensive, fact based scientific comparison for fellow Indians so far, but pls do your own verification as well.

This is Part 2 of Our 3 Part Series on – Toor Dal vs Mutton: Which Is the Better Protein – Protein Quality, Macronutrients and Why This Comparison Matters. For Part 1 – Pls Click the Link.

In the Part 1 of this Series, we extensively covered the Protein Composition, Amino Acids Comparison and Micronutrients comparisons between Toor Dal and Mutton. This piece attempts to raise the bar further with comparison on QUALITY of Protein from both protein sources by Tests called – PDCAAS and DIASS, and some more.

Why Protein Content Alone Doesn’t Tell The Whole Truth

After first glance at comparison tables in Part 1 of this series, someone might conclude: “If I simply eat more dal, I will obtain the same protein as meat.” Thoretically and Mathematically, that is possible. Physiologically, the answer is more complicated.

The body must first digest the protein into amino acids before those amino acids can be used to build muscles, enzymes, hormones and immune proteins. Two proteins containing exactly the same number of grams may produce very different biological responses depending on:

• Digestibility

• Essential amino acid composition

• Leucine concentration

• Presence of anti-nutritional factors such as phytates and tannins in Toor Dal

This is why nutrition scientists developed methods to measure protein quality, not just protein quantity.

 Why Protein Quality Matters More Than Protein Quantity

“Twenty grams of protein is not always twenty grams of usable protein” – For decades, food labels and nutrition discussions have focused almost entirely on how many grams of protein a food contains.

In the race to offer more protein per pack, you’ll see products proudly displaying claims such as:

• “20 g Protein”

• “High Protein”

• “Protein Rich”

While these claims are useful, they tell only part of the story. Imagine two different meals:

• Meal A: A generous bowl of cooked Toor Dal providing about 20 g of protein

• Meal B: A serving of cooked Mutton providing about 20 g of protein

Most people would assume these meals are nutritionally equivalent because the protein content is identical. Modern nutrition science says otherwise. The human body does not simply count grams of protein.

Instead, it evaluates how digestible the protein is, whether it contains all essential amino acids in sufficient amounts, and how efficiently those amino acids can be used to build and repair tissues.

This concept is known as protein quality, and it has become one of the most important developments in nutrition science over the past three decades.

Why Humans Need High-Quality Protein

Proteins are made from 20 amino acids, often called the building blocks of life. Our bodies can manufacture many of these amino acids, but nine essential amino acids must come from food because the human body cannot produce them in sufficient quantities. These essential amino acids are:

• Histidine

• Isoleucine

• Leucine

• Lysine

• Methionine

• Phenylalanine

• Threonine

• Tryptophan

• Valine

If even one of these amino acids is supplied in inadequate amounts, the body’s ability to build proteins is reduced. A useful analogy is building a brick wall. You may have thousands of bricks, but if you run out of cement, construction stops.

Similarly, the body cannot fully utilise dietary protein if one essential amino acid is in short supply. This is known as the limiting amino acid principle. Animal proteins such as Mutton generally contain all nine essential amino acids in proportions that closely match human requirements.

Many plant proteins—including pulses such as Toor Dal— do contain all nine essential amino acids but some of these essential amino acids are present in relatively very low concentrations, particularly the sulphur-containing amino acids methionine and cysteine. This does not make them “bad” proteins, but it does influence how efficiently the body can use these plant proteins.

What Makes One Protein Better Than Another?

Scientists evaluate protein quality using four key questions:

1. Does the food contain all essential amino acids?

2. Are those amino acids present in the right proportions?

3. How much of the protein is digested and absorbed?

4. How effectively can the absorbed amino acids be used by the body?

To answer these questions, nutrition scientists use several internationally recognised measures.

1. PDCAAS – Protein Digestibility Corrected Amino Acid Score

For many years, the Protein Digestibility Corrected Amino Acid Score (PDCAAS) was the global standard for assessing protein quality. PDCAAS combines two important factors: The amino acid composition of a protein and Its digestibility.

Scores range from 0 to 1.0, with higher values indicating better-quality protein. A protein with a PDCAAS close to 1.0 provides essential amino acids in sufficient amounts and is well digested. Typical examples of proteins with PDCAAS close to 1.0 include:

• Eggs

• Milk proteins

• Whey protein

• Meat – Mutton, Lamb

• Fish

All of these above mentioned proteins are animal source proteins. Many pulses DO have respectable PDCAAS values but generally score much lower than animal proteins because of lower digestibility and limiting amino acids.

Limitation of PDCAAS – PDCAAS estimates digestibility using faecal nitrogen measurements, which may overestimate the amount of protein actually absorbed in the small intestine. It also truncates scores at 1.0, making it difficult to distinguish between excellent proteins.

Recognising these limitations, the Food and Agriculture Organization (FAO) recommended a newer system.

2. DIAAS – Digestible Indispensable Amino Acid Score

The Digestible Indispensable Amino Acid Score (DIAAS) is now considered the most advanced method for evaluating protein quality. Unlike PDCAAS, DIAAS:

• Measures digestibility of each essential amino acid individually

• Uses absorption data from the end of the small intestine (ileum), providing a more accurate assessment

• Does not cap scores at 100, allowing truly high-quality proteins to stand out

This makes DIAAS especially useful for comparing proteins intended to support:

• Growth in children

• Muscle maintenance in older adults

• Recovery after illness

• Athletic performance

Animal proteins generally achieve MUCH higher DIAAS values because they contain abundant essential amino acids and are highly digestible. Many legumes / dals have lower DIAAS values due to lower digestibility and lower concentrations of methionine.

3. Biological Value (BV)

The Biological Value (BV) estimates how efficiently the body retains absorbed protein for building and repairing tissues. A higher BV means more of the absorbed amino acids are incorporated into body proteins rather than being broken down and excreted. Proteins with high BV are especially valuable during:

• Growth

• Pregnancy

• Recovery from surgery

• Muscle building

• Age-related muscle loss

Although BV is less commonly used today than DIAAS, it remains a useful indicator of protein efficiency.

4. Net Protein Utilisation (NPU)

Net Protein Utilisation measures the proportion of dietary protein that is both absorbed and retained by the body. It reflects the combined effects of:

• Digestibility

• Amino acid balance

• Biological utilisation

Higher NPU indicates that a greater proportion of the consumed protein contributes to body tissues.

Understanding the Major Measures of Protein Quality

Toor Dal v/s Mutton on PDCASS, DIASS, BV and NPU Parameters

Detailed Breakdown of the Metrics

1. Digestible Indispensable Amino Acid Score (DIAAS)

• Toor Dal (0.53 – 0.58): DIAAS is the current gold standard recommended by the Food and Agriculture Organization (FAO). It samples digestion at the end of the small intestine (ileum). Dal scores low because its low methionine content stops protein synthesis early, and some plant proteins pass through unabsorbed

• Cooked Mutton (1.15 – 1.30): Scores above 1.00 because it delivers an excess of every single essential amino acid relative to human requirements. It acts as an excellent “complementary protein” to raise the value of low-scoring plant foods eaten alongside it

2. Protein Digestibility-Corrected Amino Acid Score (PDCAAS)

• Toor Dal (0.60 – 0.65): PDCAAS is an older metric that measures total fecal digestibility. It overestimates plant protein quality because the large intestine can consume amino acids that your body never actually absorbed for muscle repair

• Cooked Mutton (1.00): The PDCAAS system truncates (caps) all scores at 1.00. Even though mutton vastly exceeds the baseline human requirement for amino acids, it is mathematically leveled with other complete proteins like eggs or milk

3. Biological Value (BV)

• Toor Dal (65 – 70): BV measures the percentage of absorbed nitrogen that your body retains. Out of the dal protein that successfully makes it past your gut wall, only about 65–70% can be put to work because the lack of methionine causes the remaining amino acids to be wasted or burned as energy.

• Cooked Mutton (74 – 80): Red meat has a high biological value. Nearly all of the nitrogen absorbed from the digestive tract matches human muscle tissue configurations and is incorporated smoothly into the body. [1, 2]

4. Net Protein Utilization (NPU)

• Toor Dal (50% Raw vs. 60% Cooked): NPU calculates the direct ratio of dietary protein converted into body protein. Cooking matters heavily here. Raw dal contains trypsin inhibitors that block your digestive enzymes. Boiling neutralises these compounds, lifting the usable protein utilization rate from a poor 50% up to roughly 60%

• Cooked Mutton (70 – 76%): Mutton contains no anti-nutrients or rigid plant cell walls. Your stomach acids and enzymes can cleanly break down the meat fibers, ensuring a high conversion rate into usable body tissue.

Anti-Nutritional Factors in Toor Dal – Cooking Improves the Quality of Dal

Raw pulses including Toor Dal contain key anti-nutritional factors including phytic acid, tannins, and trypsin inhibitors. These compounds bind to minerals and proteins, thus further lowering nutrient absorption from such pulses and Toor Dal.

Major Anti-Nutritional Factors

• Phytic Acid: Binds to iron, zinc, and calcium, reducing how well your body absorbs these essential minerals

• Tannins: Polyphenols that bind to proteins and digestive enzymes, lowering protein digestibility and iron availability

• Trypsin Inhibitors: Proteins that block the action of trypsin and other gut enzymes, impairing normal protein breakdown

These substances can reduce protein digestibility and mineral absorption. Fortunately, traditional Indian cooking practices significantly improve nutritional quality and overcomes some, if not all of these anti-nutritional factors. Methods employed by Indians prior to cooking Toor Dal, such as:

• Soaking

• Open Vessel cooking and removing foam

• Germination (sprouting)

• Fermentation

significantly reduce many of these antinutritional factors, increasing both protein digestibility and mineral bioavailability. This is one reason why traditional dietary practices developed over centuries remain nutritionally relevant today.

Can Vegetarians Improve Protein Quality?

Absolutely. Although Toor Dal is relatively low in methionine, cereals such as rice and wheat contain higher amounts of sulphur-containing amino acids. Conversely, cereals are relatively lower in lysine, which pulses provide in abundance.

When eaten together—as in traditional Indian meals of dal with rice or dal with chapati—the amino acid profiles complement one another, resulting in a protein quality that is substantially better than either food alone. This principle of protein complementation is one of the reasons traditional Indian dietary patterns remain nutritionally effective when they include a variety of plant foods as they used to combine Toor Dal, Rice / Chapati with Curd / Butter Milk and Paneer.

Key Takeaways

• Protein quality depends on far more than the number of grams of protein consumed

• The body requires an adequate supply of all nine essential amino acids to build and repair tissues efficiently

• Modern methods such as DIAAS provide a more accurate assessment of usable protein than older scoring systems such as PDCAAS

• Mutton provides a highly digestible, complete protein with excellent amino acid balance

• Toor Dal provides valuable plant protein but is relatively lower in methionine and cysteine

• Traditional combinations such as dal with rice or dal with chapati improve overall protein quality by complementing limiting amino acids, however, at risk of huge glycemic load in form of high amounts of carbohydrates

• For most healthy individuals, a varied, omnivore diet that combines different protein sources from animals and plants, offers the greatest nutritional benefit