Study analysis · Food Science & Nutrition · 2017
Only one cooked pulse—navy beans—met the U.S. 'Good Source of Protein' label, and it barely cleared the 10% cutoff.
Scientists fed cooked beans, peas, and lentils to rats to see how good their protein was. Most were decent, but only navy beans were good enough for a U.S. 'good source of protein' label.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study tested how well different cooked beans and peas provide protein, but they did it in rats, not people. So we can learn about the protein quality of these foods in rats, but we can't say for sure that the same exact results happen in humans. It's like testing a car in a lab instead of on the road.
What’s the bottom line?
Scientists cooked nine types of Canadian pulses (beans, peas, lentils, chickpeas) and tested how well rats could digest their protein. They wanted to see if these foods could be labeled as good protein sources in the U.S. and Canada.
How strong is this study?
The study used standard scientific methods to measure protein quality, which is good. But since it was done in animals and we don't know if the rats were randomly assigned or if the researchers knew which sample was which, we should be careful about trusting the results too much for human advice. It's a solid first step, but not the final answer.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
31 / 100
- Randomizationrandomization unclear
- Blindingblinding unclear
- Control group+15/15
- Sample sizeno sample size reported
- Follow-up+10/10
100 / 100
0 / 100
- P-valuesno p-values reported
- Effect sizeno effect size reported
- Confidence intervalsno confidence intervals
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 512 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
This design cannot establish causation — the findings describe an association, not a cause. This is an animal study (rat bioassays), not a human study. Findings cannot be directly extrapolated to humans to establish causation. No randomization or blinding reported; however, even if present, animal studies cannot establish human causation.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding statement was provided in the text, so potential conflicts cannot be assessed.
The provided text lacks a COI or funding section. The Canadian International Grains Institute prepared composite samples, but its role and funding sources are not specified. No author affiliations are given, preventing assessment of individual conflicts.
Key takeaways
- 01
Cooked pulses had true protein digestibility above 70% (black beans lowest at 70.0%, split red lentils highest at 90.6%).
- 02
PDCAAS values were above 0.5 (range 0.50 to 0.667).
- 03
DIAAS values ranged from 0.46 to 0.73, all below 0.75.
- 04
Only navy beans qualified as a U.S.
- 05
'Good Source of Protein': a 90 g serving gave 10.52% of the 50 g daily protein reference value after PDCAAS correction.
- 06
In Canada, most pulses except whole green lentils, split red lentils, and split green peas qualified as 'Source of Protein' with protein ratings 20.0–30.4 per 250 mL.
- 07
For a human: under U.S.
- 08
labeling rules, only navy beans met the 'Good Source of Protein' claim, providing about 10.5% of the daily protein reference value in a 90 g serving.
- 09
In Canada, most cooked pulses except whole green lentils, split red lentils, and split green peas met the 'Source of Protein' claim.
- 10
No pulse met the proposed FAO/WHO DIAAS 0.75 threshold.
- 11
The study did not measure human health outcomes, so absolute health effects are not reported.
Surprising findings
- Only navy beans met the U.S. 'Good Source of Protein' claim; no other cooked pulse did.Common belief is that beans, lentils, and chickpeas are all excellent protein sources, but U.S. labeling rules require corrected protein per 90 g serving to hit 10% of the daily reference value.
- No cooked pulse reached the FAO/WHO DIAAS 0.75 threshold, despite pulses being promoted as protein sources in dietary guidelines.DIAAS is a newer, proposed gold-standard protein quality score. If adopted strictly, it would undermine protein claims for all tested pulses.
- Chickpeas scored higher on DIAAS (0.67) than on PDCAAS (0.52), reversing the usual pattern.DIAAS lowered the tryptophan requirement and chickpeas are relatively high in methionine, so the same food looks better under the newer method.
- Split red lentils had the highest true protein digestibility (90.6%) but a middling PDCAAS (0.538) because sulfur amino acids were limiting.People often equate digestibility with protein quality, but amino acid profile can cap the final score regardless of how digestible the protein is.
- Chickpeas had the lowest crude protein on a dry matter basis (21.92%) but the highest adjusted PER (2.32), while split red lentils had the highest crude protein (29.51%) but a lower PER (0.98).Protein quantity and protein quality don't always align. A food can be protein-dense but not necessarily efficient for growth in the rat model.
Practical takeaways
If you want a cooked pulse that meets the U.S. 'Good Source of Protein' claim per 90 g serving, choose navy beans. They provided 10.52% of the 50 g daily reference value after PDCAAS correction.
This is based on a rat bioassay, a 90 g serving, and regulatory labeling—not a human health outcome. Larger servings may change the math.
medium-low confidenceFor Canadian 'Source of Protein' claims, most cooked pulses qualify—except whole green lentils, split red lentils, and split green peas—when served at 250 mL.
Canadian rules use PER-based Protein Ratings, which differ from U.S. PDCAAS rules. The study is animal-based.
medium confidencePair pulses with complementary proteins: if your pulse is limited by sulfur amino acids (kidney beans, green lentils, red lentils, split green peas, black beans), pair with foods rich in methionine/cysteine; if limited by tryptophan (navy beans, yellow peas, chickpeas, pinto beans), pair with tryptophan-rich foods.
In mixed diets, amino acid complementation happens naturally over the day; strict pairing at every meal is not necessary.
medium confidenceDon't expect cooked pulses to meet the proposed DIAAS 0.75 threshold for protein claims—none did in this study (range 0.46–0.73).
DIAAS was calculated using fecal digestibility, not ideal ileal digestibility, and the 0.75 cutoff is not officially adopted.
low-medium confidenceCook pulses properly to improve protein digestibility. All cooked pulses had >70% true protein digestibility, and cooking reduces trypsin inhibitors and tannins.
This study used standardized cooking; home cooking times vary and may affect digestibility.
medium confidenceFor protein density on a dry matter basis, split red lentils were highest (29.51% crude protein) and chickpeas lowest (21.92%), but chickpeas had the highest adjusted PER (2.32).
Dry matter basis doesn't reflect cooked serving size; moisture content varies widely (64–75%).
medium confidenceWhy this study matters
Navy Beans: The Only U.S. 'Good Source'
Under U.S. labeling rules, only navy beans qualified as a 'Good Source of Protein' because a 90 g serving provided 10.52% of the 50 g daily reference value after PDCAAS correction—just above the 10% threshold. All nine pulses had PDCAAS values >0.5 (absolute scores), meeting the U.S. quality-protein cutoff of >0.2, but serving size and corrected protein content separated navy beans from the rest.
Most people assume all beans and lentils are protein superstars. This study shows that under U.S. rules, only one cooked pulse actually makes the 'Good Source' cut, and by a razor-thin margin.
Canada Says Most Pulses Are 'Source of Protein'
Using Canadian Protein Rating rules, all cooked pulses except whole green lentils, split red lentils, and split green peas qualified as 'Source of Protein' with ratings between 20.0 and 30.4 per 250 mL serving. Chickpeas scored highest at 30.44; split green peas lowest at 13.17.
The same cooked pulse can be a 'Source of Protein' in Canada but fail a U.S. 'Good Source' claim. It reveals how regulatory definitions, not just nutrition, shape food labels.
DIAAS: No Pulse Passes 0.75
DIAAS values ranged from 0.46 (split green peas) to 0.73 (split yellow peas), and none reached the FAO/WHO proposed 0.75 threshold for allowing a protein claim. Yet dietary guidelines in Canada and the U.S. position pulses as protein sources.
If regulators adopted the DIAAS 0.75 cutoff, virtually no cooked pulse could carry a protein claim—directly contradicting mainstream dietary advice.
Limiting Amino Acids Flip Between Pulses
Sulfur amino acids (methionine + cysteine) were first limiting for red kidney beans, whole green lentils, split red lentils, split green peas, and black beans. Tryptophan was first limiting for navy beans, split yellow peas, chickpeas, and pinto beans.
Not all plant proteins are limited by the same amino acid. This matters for pairing pulses with complementary foods to complete the protein profile.
Chickpeas: DIAAS Beats PDCAAS
Chickpeas had a PDCAAS of 0.519 but a DIAAS of 0.67—higher under DIAAS—because DIAAS uses a lower tryptophan requirement and chickpeas have relatively high methionine. Split red lentils had the highest true protein digestibility (90.6%) but a PDCAAS of only 0.538 due to limiting sulfur amino acids.
Protein quality rankings can flip depending on the scoring system. A pulse that looks mediocre under PDCAAS may look better under DIAAS, and vice versa.
Digestibility Varies: Black Beans Lowest, Red Lentils Highest
True protein digestibility was >70% for all cooked pulses, but black beans were lowest at 70.0% and split red lentils highest at 90.6%. The study suggests black beans' lower digestibility may relate to phenolic fractions.
Even within the same food family, digestibility varies widely. If you're relying on black beans for protein, you may absorb less than from red lentils.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists cooked nine types of Canadian pulses (beans, peas, lentils, chickpeas) and tested how well rats could digest their protein. They wanted to see if these foods could be labeled as good protein sources in the U.S. and Canada.
Research results
Cooked pulses had true protein digestibility above 70% (black beans lowest at 70.0%, split red lentils highest at 90.6%). PDCAAS values were above 0.5 (range 0.50 to 0.667). DIAAS values ranged from 0.46 to 0.73, all below 0.75. Only navy beans qualified as a U.S. 'Good Source of Protein': a 90 g serving gave 10.52% of the 50 g daily protein reference value after PDCAAS correction. In Canada, most pulses except whole green lentils, split red lentils, and split green peas qualified as 'Source of Protein' with protein ratings 20.0–30.4 per 250 mL.
What this means - more context
For a human: under U.S. labeling rules, only navy beans met the 'Good Source of Protein' claim, providing about 10.5% of the daily protein reference value in a 90 g serving. In Canada, most cooked pulses except whole green lentils, split red lentils, and split green peas met the 'Source of Protein' claim. No pulse met the proposed FAO/WHO DIAAS 0.75 threshold. The study did not measure human health outcomes, so absolute health effects are not reported.
This study determined protein digestibility-corrected amino acid score (PDCAAS) and protein efficiency ratio (PER) of nine cooked Canadian pulse classes to support protein quality claims in Canada and the United States. Digestible indispensable amino acid score (DIAAS) was also calculated for comparison.
Cooked Canadian pulses had high true protein digestibility, all >70%, with black beans lowest (70.0%) and split red lentils highest (90.6%). PDCAAS values were >0.5 (range 0.50 for split green peas to 0.667 for navy beans), meeting the U.S. regulatory threshold (>0.2) for a quality protein. Only navy beans qualified as a U.S. 'Good Source of Protein' (90 g serving provided 10.52% of the 50 g daily reference value after PDCAAS correction). Under Canadian rules, all pulses except whole green lentils, split red lentils, and split green peas qualified as 'Source of Protein' with protein ratings 20.0–30.4 per 250 mL serving. DIAAS values ranged 0.46 (split green peas) to 0.73 (split yellow peas), and none reached the FAO/WHO 0.75 threshold for a protein content claim.
Methods Used
Composite pulse samples from the 2010 Canadian crop were cooked and freeze-dried. True protein digestibility and PDCAAS were measured by rat bioassay using casein as reference and a protein-free diet to correct for endogenous nitrogen losses. PER was measured over a 28-day growth period in male weanling rats (n=8–10 per treatment). Amino acid composition was determined by AOAC methods. DIAAS was calculated using fecal true protein digestibility and the 2013 FAO/WHO child reference pattern.
Main Finding
All nine cooked pulses had true protein digestibility >70% and PDCAAS >0.5, qualifying as quality proteins in the U.S. Only navy beans met the U.S. 'Good Source of Protein' claim: a 90 g serving provided 10.52% of the 50 g daily protein reference value after PDCAAS correction. In Canada, all pulses except whole green lentils, split red lentils, and split green peas met 'Source of Protein' with protein ratings 20.0–30.4 per 250 mL. No pulse reached the FAO/WHO DIAAS 0.75 threshold (range 0.46–0.73). Sulfur amino acids were first limiting for red kidney beans, whole green lentils, split red lentils, split green peas, and black beans; tryptophan was first limiting for navy beans, split yellow peas, chickpeas, and pinto beans.
Confidence Level
Moderate. The study used standard AOAC rat bioassay methods and casein reference, but it is an animal study with small group sizes, no reported randomization, no p-values, no confidence intervals, and DIAAS was calculated using fecal rather than ileal digestibility. Results are relevant for regulatory protein claims, not direct human health outcomes.
Study Flags
Red Flags
- •Rat bioassay, not a human study
- •Small sample size per group (n=8–10 rats) and no randomization reported
- •No p-values or confidence intervals reported; DIAAS used fecal rather than ileal digestibility
Surprising Findings
Only navy beans met the U.S. 'Good Source of Protein' claim; no other cooked pulse did.
Common belief is that beans, lentils, and chickpeas are all excellent protein sources, but U.S. labeling rules require corrected protein per 90 g serving to hit 10% of the daily reference value.
Practical Takeaways
If you want a cooked pulse that meets the U.S. 'Good Source of Protein' claim per 90 g serving, choose navy beans. They provided 10.52% of the 50 g daily reference value after PDCAAS correction.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 512 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Animal Cohort Study
Subject
Lower probability
on the GRADE evidence scale
This study tested how well different cooked beans and peas provide protein, but they did it in rats, not people. So we can learn about the protein quality of these foods in rats, but we can't say for sure that the same exact results happen in humans. It's like testing a car in a lab instead of on the road.
Strengths
- Used standard AOAC methods for protein quality determination
- Included a reference protein (casein) for comparison
- Tested multiple pulse classes (nine types)
Weaknesses
- Animal study, not human
- No randomization or blinding reported
- Small sample size per group
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Scientists cooked nine types of Canadian pulses (beans, peas, lentils, chickpeas) and tested how well rats could digest their protein. They wanted to see if these foods could be labeled as good protein sources in the U.S. and Canada.
Research results
Cooked pulses had true protein digestibility above 70% (black beans lowest at 70.0%, split red lentils highest at 90.6%). PDCAAS values were above 0.5 (range 0.50 to 0.667). DIAAS values ranged from 0.46 to 0.73, all below 0.75. Only navy beans qualified as a U.S. 'Good Source of Protein': a 90 g serving gave 10.52% of the 50 g daily protein reference value after PDCAAS correction. In Canada, most pulses except whole green lentils, split red lentils, and split green peas qualified as 'Source of Protein' with protein ratings 20.0–30.4 per 250 mL.
What this means - more context
For a human: under U.S. labeling rules, only navy beans met the 'Good Source of Protein' claim, providing about 10.5% of the daily protein reference value in a 90 g serving. In Canada, most cooked pulses except whole green lentils, split red lentils, and split green peas met the 'Source of Protein' claim. No pulse met the proposed FAO/WHO DIAAS 0.75 threshold. The study did not measure human health outcomes, so absolute health effects are not reported.
This study determined protein digestibility-corrected amino acid score (PDCAAS) and protein efficiency ratio (PER) of nine cooked Canadian pulse classes to support protein quality claims in Canada and the United States. Digestible indispensable amino acid score (DIAAS) was also calculated for comparison.
Cooked Canadian pulses had high true protein digestibility, all >70%, with black beans lowest (70.0%) and split red lentils highest (90.6%). PDCAAS values were >0.5 (range 0.50 for split green peas to 0.667 for navy beans), meeting the U.S. regulatory threshold (>0.2) for a quality protein. Only navy beans qualified as a U.S. 'Good Source of Protein' (90 g serving provided 10.52% of the 50 g daily reference value after PDCAAS correction). Under Canadian rules, all pulses except whole green lentils, split red lentils, and split green peas qualified as 'Source of Protein' with protein ratings 20.0–30.4 per 250 mL serving. DIAAS values ranged 0.46 (split green peas) to 0.73 (split yellow peas), and none reached the FAO/WHO 0.75 threshold for a protein content claim.
Methods Used
Composite pulse samples from the 2010 Canadian crop were cooked and freeze-dried. True protein digestibility and PDCAAS were measured by rat bioassay using casein as reference and a protein-free diet to correct for endogenous nitrogen losses. PER was measured over a 28-day growth period in male weanling rats (n=8–10 per treatment). Amino acid composition was determined by AOAC methods. DIAAS was calculated using fecal true protein digestibility and the 2013 FAO/WHO child reference pattern.
Main Finding
All nine cooked pulses had true protein digestibility >70% and PDCAAS >0.5, qualifying as quality proteins in the U.S. Only navy beans met the U.S. 'Good Source of Protein' claim: a 90 g serving provided 10.52% of the 50 g daily protein reference value after PDCAAS correction. In Canada, all pulses except whole green lentils, split red lentils, and split green peas met 'Source of Protein' with protein ratings 20.0–30.4 per 250 mL. No pulse reached the FAO/WHO DIAAS 0.75 threshold (range 0.46–0.73). Sulfur amino acids were first limiting for red kidney beans, whole green lentils, split red lentils, split green peas, and black beans; tryptophan was first limiting for navy beans, split yellow peas, chickpeas, and pinto beans.
Confidence Level
Moderate. The study used standard AOAC rat bioassay methods and casein reference, but it is an animal study with small group sizes, no reported randomization, no p-values, no confidence intervals, and DIAAS was calculated using fecal rather than ileal digestibility. Results are relevant for regulatory protein claims, not direct human health outcomes.
Study Flags
Red Flags
- •Rat bioassay, not a human study
- •Small sample size per group (n=8–10 rats) and no randomization reported
- •No p-values or confidence intervals reported; DIAAS used fecal rather than ileal digestibility
Surprising Findings
Only navy beans met the U.S. 'Good Source of Protein' claim; no other cooked pulse did.
Common belief is that beans, lentils, and chickpeas are all excellent protein sources, but U.S. labeling rules require corrected protein per 90 g serving to hit 10% of the daily reference value.
Practical Takeaways
If you want a cooked pulse that meets the U.S. 'Good Source of Protein' claim per 90 g serving, choose navy beans. They provided 10.52% of the 50 g daily reference value after PDCAAS correction.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 512 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
Animal Cohort Study
Subject
Lower probability
on the GRADE evidence scale
This study tested how well different cooked beans and peas provide protein, but they did it in rats, not people. So we can learn about the protein quality of these foods in rats, but we can't say for sure that the same exact results happen in humans. It's like testing a car in a lab instead of on the road.
Strengths
- Used standard AOAC methods for protein quality determination
- Included a reference protein (casein) for comparison
- Tested multiple pulse classes (nine types)
Weaknesses
- Animal study, not human
- No randomization or blinding reported
- Small sample size per group
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The study used standard scientific methods to measure protein quality, which is good. But since it was done in animals and we don't know if the rats were randomly assigned or if the researchers knew which sample was which, we should be careful about trusting the results too much for human advice. It's a solid first step, but not the final answer.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
31 / 100
- Randomizationrandomization unclear
- Blindingblinding unclear
- Control group+15/15
- Sample sizeno sample size reported
- Follow-up+10/10
100 / 100
0 / 100
- P-valuesno p-values reported
- Effect sizeno effect size reported
- Confidence intervalsno confidence intervals
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 512 / 100
Probability of being correct
Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.
This design cannot establish causation — the findings describe an association, not a cause. This is an animal study (rat bioassays), not a human study. Findings cannot be directly extrapolated to humans to establish causation. No randomization or blinding reported; however, even if present, animal studies cannot establish human causation.
COI Unknown
Could not determine conflict of interest status
No conflict of interest or funding statement was provided in the text, so potential conflicts cannot be assessed.
The provided text lacks a COI or funding section. The Canadian International Grains Institute prepared composite samples, but its role and funding sources are not specified. No author affiliations are given, preventing assessment of individual conflicts.
Standing
The people behind it
The researchers who wrote the study this analysis is built on.
Authored by
6 researchersIf this is your work, this is how we attribute it on Fit Body Science. Matthew G. Nosworthy is listed as the lead author.
- James D. HouseCorresponding