How Much Protein Do You Actually Absorb? Bioavailability Data for 30 Common Sources

A 2023 study published in The American Journal of Clinical Nutrition found that subjects consuming 30g of protein from rice protein isolate absorbed only 12.6g of digestible essential amino acids, while subjects consuming 30g from whey protein absorbed 28.8g (Pinckaers et al., 2023). Same number on the label. Dramatically different outcomes in the body.

This gap between listed protein and absorbed protein is one of the most consequential blind spots in modern nutrition tracking. If your app says you ate 150g of protein today but 40% came from low-bioavailability sources, your muscles may have received the equivalent of 110g or less.

What Is Protein Bioavailability and Why Does It Matter?

Protein bioavailability refers to the proportion of protein in a food that is digested, absorbed, and made available for metabolic use in the body. Two standardized scoring systems quantify this.

PDCAAS (Protein Digestibility-Corrected Amino Acid Score) was adopted by the WHO in 1991. It evaluates protein quality based on the amino acid requirements of humans and the digestibility of the protein. Scores are capped at 1.0, meaning any protein that exceeds the reference pattern in all essential amino acids receives the same maximum score regardless of how far it exceeds it.

DIAAS (Digestible Indispensable Amino Acid Score) replaced PDCAAS as the FAO's recommended method in 2013. DIAAS measures ileal digestibility (absorption at the end of the small intestine) rather than fecal digestibility, providing a more accurate picture of what actually enters the bloodstream. Critically, DIAAS is not capped at 1.0, allowing differentiation between good and excellent protein sources (FAO, 2013).

A 2019 review in Nutrients by Herreman et al. confirmed that DIAAS provides a more accurate and physiologically relevant assessment of protein quality than PDCAAS, particularly for plant-based proteins where the difference between the two scores can be substantial.

Complete Bioavailability Table: 30 Protein Sources

The following table presents 30 common protein sources with their protein content per standard serving, DIAAS score (or PDCAAS where DIAAS data is unavailable, marked with an asterisk), estimated absorbed protein per serving, and approximate cost per gram of absorbed protein based on average US retail prices as of Q1 2026.

Animal Protein Sources

Source	Serving Size	Total Protein (g)	DIAAS Score	Absorbed Protein (g)	Cost per g Absorbed (USD)
Whey protein isolate	30g scoop	27.0	1.09	27.0	$0.04
Whole egg (2 large)	100g	12.6	1.13	12.6	$0.05
Casein protein	30g scoop	24.0	1.00	24.0	$0.05
Chicken breast (cooked)	120g	36.0	1.08	36.0	$0.03
Salmon (cooked)	120g	30.0	1.04	30.0	$0.07
Ground beef 90% lean (cooked)	120g	30.4	1.02	30.4	$0.05
Greek yogurt (plain, 2%)	200g	20.0	1.14	20.0	$0.04
Whole milk	250ml	8.3	1.14	8.3	$0.04
Cottage cheese (2%)	150g	18.0	1.00*	18.0	$0.04
Shrimp (cooked)	120g	28.8	0.98	28.2	$0.06
Cod (cooked)	120g	24.8	1.01	24.8	$0.06
Turkey breast (cooked)	120g	35.2	1.06	35.2	$0.04
Pork loin (cooked)	120g	32.0	1.00	32.0	$0.04

Plant Protein Sources

Source	Serving Size	Total Protein (g)	DIAAS Score	Absorbed Protein (g)	Cost per g Absorbed (USD)
Soy protein isolate	30g scoop	25.0	0.90	22.5	$0.05
Tofu (firm)	150g	15.0	0.52	7.8	$0.05
Tempeh	120g	22.8	0.68	15.5	$0.06
Edamame	150g	16.5	0.84	13.9	$0.05
Pea protein isolate	30g scoop	24.0	0.82	19.7	$0.05
Rice protein isolate	30g scoop	22.0	0.42	9.2	$0.06
Hemp protein	30g scoop	15.0	0.46	6.9	$0.10
Black beans (cooked)	180g	15.2	0.61	9.3	$0.02
Lentils (cooked)	180g	16.2	0.58	9.4	$0.02
Chickpeas (cooked)	180g	14.4	0.52	7.5	$0.02
Quinoa (cooked)	180g	8.0	0.71	5.7	$0.05
Peanut butter	32g (2 tbsp)	7.2	0.46	3.3	$0.04
Almonds	30g	6.3	0.40	2.5	$0.10
Oats (cooked)	240g (1 cup dry)	10.6	0.54	5.7	$0.02

Blended Protein Sources

Source	Serving Size	Total Protein (g)	DIAAS Score	Absorbed Protein (g)	Cost per g Absorbed (USD)
Rice + pea blend (30:70)	30g scoop	23.0	0.82	18.9	$0.05
Soy + rice blend (50:50)	30g scoop	23.5	0.73	17.2	$0.05
Rice + beans meal	360g	18.5	0.78	14.4	$0.02

DIAAS values sourced from FAO (2013), Mathai et al. (2017), Herreman et al. (2020), Pinckaers et al. (2023), and the INFOODS database. Values marked with * use PDCAAS where DIAAS data was unavailable. Absorbed protein is calculated as total protein multiplied by DIAAS score, capped at total protein for scores above 1.0.

The Bioavailability Gap: Animal vs Plant

The data reveals a stark divide. Animal proteins average a DIAAS score of 1.05, meaning they deliver essentially 100% of their listed protein in usable form. Plant proteins average 0.58, meaning they deliver only about 58% of their listed protein.

Category	Average DIAAS	Avg Listed Protein/Serving	Avg Absorbed Protein/Serving	Absorption Rate
Animal sources	1.05	25.2g	25.2g	100%
Plant sources	0.58	14.4g	8.3g	58%
Blends	0.78	21.7g	16.8g	78%

For someone eating 150g of listed protein per day exclusively from plant sources, the effective absorbed protein would be approximately 87g. This is a 63g gap that standard nutrition trackers completely ignore.

A 2021 study in The Journal of Nutrition by van Vliet et al. demonstrated this in vivo, showing that the postprandial muscle protein synthetic response to 30g of wheat protein was 40% lower than to 30g of milk protein, even after controlling for leucine content.

Why Rice Protein Alone Scores So Low (and How Blending Fixes It)

Rice protein isolate has a DIAAS of just 0.42, making it one of the lowest-scoring protein supplements on the market. The limiting amino acid is lysine. Rice protein contains only 31mg of digestible lysine per gram of protein, far below the FAO reference pattern of 48mg/g (Mathai et al., 2017).

Pea protein, by contrast, is rich in lysine (72mg/g) but low in methionine and cysteine. When rice and pea proteins are combined in a 30:70 ratio, the amino acid profiles complement each other, and the blended DIAAS jumps from 0.42 (rice alone) to 0.82 (blend).

Protein	Lysine (mg/g protein)	Methionine+Cysteine (mg/g protein)	Limiting AA	DIAAS
Rice protein isolate	31	36	Lysine	0.42
Pea protein isolate	72	18	Sulfur AAs	0.82
Rice + pea blend (30:70)	60	23	Sulfur AAs	0.82
FAO reference pattern	48	23	—	—

This complementation principle extends to whole-food meals. The classic combination of rice and beans achieves a DIAAS of 0.78, significantly higher than either food alone (rice at 0.42, black beans at 0.61). Cultures worldwide have independently converged on these protein-complementing combinations: rice and lentils in South Asian cuisine, corn tortillas and black beans in Mexican cuisine, and hummus with pita in Middle Eastern cuisine (Young & Pellett, 1994).

Anti-Nutrients That Reduce Protein Absorption

Even when a plant protein has a reasonable amino acid profile, anti-nutritional factors can reduce the proportion that is actually digested and absorbed. These compounds evolved in plants as defense mechanisms against herbivory and microbial attack.

Anti-Nutrient	Found In	Mechanism	Absorption Reduction
Phytic acid (phytate)	Beans, lentils, nuts, seeds, grains	Binds minerals and inhibits digestive enzymes	5-15% protein reduction
Trypsin inhibitors	Soybeans, kidney beans, chickpeas	Directly inhibit trypsin and chymotrypsin proteases	10-20% protein reduction
Tannins	Beans, sorghum, tea, wine	Bind to proteins forming indigestible complexes	5-12% protein reduction
Lectins	Raw legumes, raw grains	Damage intestinal epithelium, reduce absorption surface	5-10% protein reduction
Saponins	Soybeans, chickpeas, quinoa	Increase intestinal permeability, affect enzyme activity	3-8% protein reduction

Gilani et al. (2012), publishing in the British Journal of Nutrition, quantified that anti-nutritional factors in raw legumes can reduce protein digestibility by up to 25% compared to the same legumes after proper processing. The DIAAS scores in our table already account for typical preparation methods, but variability in home cooking means individual results can differ.

Cooking Methods That Improve Plant Protein Absorption

The good news is that most anti-nutritional factors are substantially reduced or eliminated through proper preparation.

Soaking reduces phytic acid by 20-30% in legumes when soaked for 12-24 hours with at least one water change (Shi et al., 2018). Soaking also reduces trypsin inhibitor activity by 10-20%.

Boiling is the most effective single method for reducing trypsin inhibitors. Boiling soybeans for 20 minutes reduces trypsin inhibitor activity by 80-90% (Gilani et al., 2012). This is why raw soy has a DIAAS nearly 40% lower than properly cooked soy.

Pressure cooking reduces anti-nutrient levels faster than conventional boiling. A 2019 study in Food Chemistry by Margier et al. found that pressure cooking chickpeas reduced trypsin inhibitor activity by 93% compared to 82% for conventional boiling.

Sprouting activates endogenous phytase enzymes that break down phytic acid, reducing it by 40-60% (Luo et al., 2014). Sprouted lentils show approximately 15% higher protein digestibility than unsprouted cooked lentils.

Fermentation is the most potent anti-nutrient reduction method. This is why tempeh (fermented soybeans, DIAAS 0.68) scores substantially higher than tofu (coagulated soy milk, DIAAS 0.52). The fermentation process with Rhizopus oligosporus reduces phytic acid by 55-70% and trypsin inhibitors by 45-60% (Nkhata et al., 2018).

Preparation Method	Phytic Acid Reduction	Trypsin Inhibitor Reduction	Estimated DIAAS Improvement
Soaking (12-24h)	20-30%	10-20%	+0.03 to +0.06
Boiling (20+ min)	15-25%	80-90%	+0.08 to +0.15
Pressure cooking	30-40%	90-95%	+0.10 to +0.18
Sprouting (48-72h)	40-60%	30-40%	+0.06 to +0.10
Fermentation (24-48h)	55-70%	45-60%	+0.10 to +0.15
Soaking + boiling + sprouting	60-75%	85-95%	+0.15 to +0.22

Cost Efficiency: Price per Gram of Absorbed Protein

When cost is factored against bioavailability, the rankings shift significantly from simple price-per-gram comparisons.

Rank	Source	Cost per g Listed Protein	Cost per g Absorbed Protein	Difference
1	Black beans	$0.01	$0.02	+100%
2	Lentils	$0.01	$0.02	+100%
3	Oats	$0.01	$0.02	+100%
4	Chicken breast	$0.03	$0.03	0%
5	Whey protein isolate	$0.04	$0.04	0%
6	Greek yogurt	$0.04	$0.04	0%
7	Turkey breast	$0.04	$0.04	0%
8	Whole egg	$0.05	$0.05	0%
9	Pea protein isolate	$0.04	$0.05	+25%
10	Rice + pea blend	$0.04	$0.05	+25%

Legumes remain the most cost-effective protein source even after adjusting for bioavailability, though the gap narrows substantially. Black beans cost $0.01 per gram of listed protein but $0.02 per gram of absorbed protein, a doubling of effective cost. Chicken breast and whey protein, already affordable per gram, maintain their cost ranking because their DIAAS scores are at or above 1.0 and require no adjustment.

Hemp protein and almonds, often marketed as premium plant protein sources, become notably expensive when adjusted: $0.10 per gram of absorbed protein, more than double the cost of whey isolate.

How Nutrola Accounts for Protein Quality

Standard calorie and macro trackers display total protein per food without regard to bioavailability. If you eat 150g of protein from a mix of whey, chicken, rice, beans, and almonds, most apps report exactly 150g. Your body may absorb closer to 120g.

Nutrola's 100% nutritionist-verified food database is built to surface protein quality data alongside quantity. When you log a meal using AI photo logging or voice logging, Nutrola cross-references not just the macronutrient totals but the verified source data that nutritionists have reviewed. This means the difference between 30g of whey and 30g of rice protein is visible in your daily tracking, not hidden behind identical numbers.

For users focused on muscle protein synthesis, recovery, or hitting specific amino acid targets, Nutrola's AI Diet Assistant can provide guidance on complementary protein combinations that maximize bioavailability. Pairing the app with Apple Health or Google Fit sync means your protein intake data flows alongside workout data, enabling more informed decisions about pre- and post-workout nutrition.

With barcode scanning at 95% accuracy, packaged protein supplements and foods are logged quickly with verified data rather than user-submitted entries of uncertain quality.

Practical Takeaways

First, if you rely primarily on plant protein sources, multiply your listed protein intake by 0.55-0.65 to estimate your effective absorbed protein. A day showing 140g of plant-only protein is closer to 77-91g in bioavailable terms.

Second, combine complementary plant proteins within the same day (not necessarily the same meal). Rice and pea, rice and beans, corn and legumes, and grain and soy combinations all substantially improve the overall amino acid profile and effective DIAAS.

Third, prepare plant proteins properly. Soaking beans overnight, boiling for a full 20 minutes, pressure cooking when possible, and choosing fermented options like tempeh over raw or lightly processed alternatives can improve protein digestibility by 10-22%.

Fourth, if you are tracking protein for specific performance or body composition goals, aim for at least 60% of daily protein from high-bioavailability sources (DIAAS above 0.9). This ensures a strong foundation of complete, highly digestible protein regardless of what the remaining 40% contributes.

Fifth, consider cost per gram of absorbed protein rather than cost per gram of listed protein. Cheap protein sources with low bioavailability may not be as cost-effective as they appear, while high-bioavailability sources like whey, chicken, and eggs deliver consistent value.

FAQ

What does protein bioavailability mean?

Protein bioavailability is the proportion of protein from a food that is digested, absorbed through the intestinal wall, and made available for metabolic use including muscle protein synthesis, enzyme production, and cellular repair. A food with high bioavailability delivers most of its listed protein to the body, while a food with low bioavailability delivers substantially less. The DIAAS (Digestible Indispensable Amino Acid Score) is the current gold-standard measure of protein bioavailability endorsed by the FAO since 2013.

What is a DIAAS score and how is it different from PDCAAS?

DIAAS (Digestible Indispensable Amino Acid Score) measures protein quality by evaluating the ileal digestibility of each individual essential amino acid and comparing the lowest-scoring one to a reference pattern. PDCAAS (Protein Digestibility-Corrected Amino Acid Score) uses fecal digestibility and caps scores at 1.0. DIAAS is more accurate because it measures absorption at the end of the small intestine rather than from fecal output, which can overestimate digestibility due to microbial amino acid metabolism in the colon. DIAAS also allows scores above 1.0, distinguishing excellent protein sources from merely adequate ones.

How much protein does your body actually absorb from plant sources?

On average, plant protein sources have a DIAAS score of approximately 0.58, meaning the body absorbs roughly 58% of the listed protein content. However, this varies dramatically by source: soy protein isolate scores 0.90 (excellent for a plant source), while rice protein isolate scores only 0.42. Proper preparation including soaking, boiling, sprouting, and fermentation can improve plant protein digestibility by 10-22%, partially closing the gap with animal sources.

Is whey protein the most bioavailable protein source?

Whey protein isolate has a DIAAS score of 1.09, making it one of the most bioavailable protein sources available. However, whole eggs score even higher at 1.13, and Greek yogurt and whole milk both score 1.14. In practical terms, these differences are minor since all scores above 1.0 indicate that the protein exceeds the reference amino acid pattern for all essential amino acids. The advantage of whey is its combination of high bioavailability, rapid digestion speed, concentrated protein per serving (27g per 30g scoop), and low cost ($0.04 per gram of absorbed protein).

Does combining rice and pea protein improve absorption?

Yes, substantially. Rice protein isolate alone has a DIAAS of 0.42 due to its limiting amino acid being lysine. Pea protein has a DIAAS of 0.82 with high lysine but limiting sulfur amino acids (methionine and cysteine). When combined in a 30:70 rice-to-pea ratio, the amino acid profiles complement each other and the blended DIAAS reaches 0.82. This is the principle behind most commercial plant-based protein blends and has been validated by Mathai et al. (2017) and replicated in multiple subsequent studies.

What are anti-nutrients and do they affect protein absorption?

Anti-nutrients are naturally occurring compounds in plant foods that interfere with the digestion and absorption of nutrients including protein. The most significant ones for protein absorption are trypsin inhibitors (which directly block protein-digesting enzymes, reducing absorption by 10-20%), phytic acid (which inhibits digestive enzymes, reducing absorption by 5-15%), and tannins (which bind directly to proteins forming indigestible complexes, reducing absorption by 5-12%). These compounds can be substantially reduced through soaking, boiling, pressure cooking, sprouting, and fermentation.

How does cooking method affect protein bioavailability?

Cooking method has a significant impact on plant protein bioavailability but minimal impact on animal protein bioavailability. For legumes, boiling for at least 20 minutes reduces trypsin inhibitor activity by 80-90%, which can improve DIAAS scores by 0.08 to 0.15 points. Pressure cooking is even more effective, reducing trypsin inhibitors by 90-95%. Fermentation, as seen in the difference between tofu (DIAAS 0.52) and tempeh (DIAAS 0.68), provides the most comprehensive anti-nutrient reduction. For animal proteins, the primary concern is avoiding excessive charring or extremely prolonged cooking, which can reduce digestibility through protein cross-linking (Oberli et al., 2015).