Protein quality is not a single number on a label. The figure you read — "10 g protein" — tells you the quantity only. The real benefit is decided by two other things: how much of that protein is actually digested and absorbed, and whether it supplies the essential amino acids in the proportions your body needs. That is why 10 g from one source can do more for you than 10 g from another, and it is the substantive difference between plant and animal protein that most articles skip.
This guide unpacks it calmly and with evidence: how protein is measured scientifically, why the Food and Agriculture Organization changed the official metric, where the "incomplete protein" myth breaks down, and how much you actually need per day — and per meal. The goal is not to sell you one source over another. It is to let you read the label with different eyes. 🔍
What does the protein number on the label actually measure?
The figure printed in the nutrition panel represents the crude quantity of protein in a serving. It is a purely quantitative number, and while it is useful, it is incomplete, because it answers neither of two decisive questions:
- How much of that protein actually reaches your bloodstream? Some protein passes through the digestive tract without being fully absorbed, and the proportion differs from food to food.
- Does its composition match what your body needs? Protein is not one substance but a chain of amino acids, and there are nine your body cannot manufacture on its own.
MedlinePlus, from the U.S. National Library of Medicine, puts it plainly: "The 9 essential amino acids are: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine," and these are amino acids that "cannot be made by the body. As a result, they must come from food."
In practice, protein behaves like a work crew: if one member is missing, the job stops at that member's limit no matter how many others show up. Nutrition scientists call this the limiting amino acid.
Protein quality: two equations, not one
To evaluate any protein, scientists combine two elements: digestibility and amino acid composition. The 2025 position paper of the Academy of Nutrition and Dietetics phrases it precisely: "Protein quality is a product of the digestibility and EAA profile of a protein source, and the amino acid requirements of the individual."
Notice the third element in that definition: the requirements of the individual. An infant, an athletic adult and an older person are not held to the same standard — a point we return to below.
From PDCAAS to DIAAS: why the metric changed
For decades the official measure of protein quality was PDCAAS (Protein Digestibility-Corrected Amino Acid Score). It carries two well-documented flaws, described by Mathai, Liu and Stein in the British Journal of Nutrition in 2017:
- It measures digestion in the wrong place. PDCAAS values "are calculated from the total tract digestibility of crude protein (CP)," whereas "digestibility of AA is most correctly determined at the end of the small intestine (the ileum)." This is not an academic quibble: colonic bacteria consume and alter amino acids, so digestibility looks higher than what actually reached you.
- It truncates scores at 100%. Any protein scoring above 100 is cut back to 100. On paper a protein scoring 100 and one scoring 120 become identical, and the superior protein is denied credit "based on its value as a complementary source of AA" for other foods in the same meal.
For those reasons the FAO's 2013 report on dietary protein quality evaluation in human nutrition recommended moving to DIAAS (Digestible Indispensable Amino Acid Score), which uses "standardised ileal digestibility (SID) of amino acids" rather than faecal values, does not truncate at 100, and accounts for each amino acid separately instead of assuming they are all digested at the rate of crude protein.
What do the numbers say?
The FAO set three categories for classifying protein quality by DIAAS, for older children, adolescents and adults:
- Excellent / high quality: DIAAS of 100 or above.
- Good quality: DIAAS of 75 to below 100.
- Below the recommendation: DIAAS under 75.
In the measurements published by Mathai and colleagues, the results came out as follows (values calculated against a reference pattern for young children; figures shift somewhat with the reference pattern used):
Milk protein concentrate: 120
Whey protein concentrate: 107
Skimmed milk powder: 105
Whey protein isolate: 100
Soya flour: 89
Soya protein isolate: 84
Pea protein concentrate: 62
Wheat: 45
These numbers tell two stories at once. The first is that dairy sources head the list. The second — the one usually missed — is that the spread within the plant world is enormous: soy sits in the "good" band and approaches excellent, while wheat sits at 45 in the lowest band. In other words, the phrase "plant protein" by itself means very little. What matters is which plant.
Is plant protein "incomplete"? A half-true myth
You will often read that plant proteins are "incomplete" because they lack essential amino acids. That phrasing is inaccurate, and the correction matters.
All nine are present — in differing amounts
The Academy of Nutrition and Dietetics position paper (2025) states it directly: "Although plant-based proteins contain all EAAs required by the body, they generally exhibit lower digestibility and may be low in specific EAAs such as lysine and methionine."
So the issue is not the absence of an amino acid but a lower amount of it, alongside lower digestibility. That difference changes both the meaning and the action: you do not need to "fix" a deficiency, you need variety and a slightly larger quantity.
The same paper notes that soy is a clear exception: "Soy is considered a high-quality protein that is well digested and has an EAA pattern that resembles animal-sourced protein because it closely matches human requirements."
The protein-combining myth
The famous rule says you must pair rice with beans in the same meal for the protein to be complete. Science has moved past that rule.
MedlinePlus is explicit: "A diet based on a single plant item will not be adequate, but we no longer worry about pairing proteins (such as beans with rice) at a single meal." The Academy paper explains why: "this is not of concern for most individuals because there is considerable variation in amino acid composition among protein-rich plant foods allowing for adequate consumption of all EAAs over the course of a day in a varied diet that meets energy requirements."
The operative phrase is "over the course of a day", not "in a single meal." Your body maintains a continually refreshed pool of amino acids that allows matching to happen between meals. What survives from the old rule is variety; what has fallen away is the timing.
One practical caution for anyone eating low-carb: the traditional version of "combining" leans on grains, which are simultaneously the weakest protein sources by quality (wheat at 45). The variety you need does not run through refined grains at all — it runs through nuts, seeds, legumes, soy, and dairy and eggs for those who eat them.
The dose per meal, not just per day
Most people think about protein as a daily total. But muscle research indicates that how protein is distributed across meals matters too.
The leucine threshold
Among the nine essential amino acids, leucine acts as the ignition key for muscle protein synthesis. A 2024 review in Frontiers in Nutrition reports that the minimum leucine for optimal stimulation of muscle protein synthesis is around 2.5 g per meal — roughly 7.5 g per day, which is "nearly 3 times the minimum RDA."
This is a practically important point in the plant-versus-animal comparison: because plant sources are generally less concentrated in leucine and less digestible, reaching the same threshold requires a larger portion. That does not make it unachievable — it means a small serving will not do it.
Older adults: anabolic resistance
With age, muscle responds less readily to protein — a phenomenon known as anabolic resistance. The same review describes it this way: "aging results in a decreased response of MPS to a protein meal but… the age-related decline in efficiency could be overcome by increasing the EAA content," and notes that older adults (over 60) "require meals with at least 2.8 g of leucine (~30 g of protein)," with a daily recommendation of 1.2–1.6 g per kilogram versus 0.8 in the general guideline.
The review also reports that "balanced meal distribution produced greater net 24-h MPS than the unbalanced distribution" — three moderate-protein meals beat one enormous dinner and a near-empty day.
Protein alone does not build muscle
This is the fact that disappears in supplement advertising. A large meta-analysis published in Sports Medicine – Open in 2022, covering 82 studies and 3,940 participants, concluded that "concurrent use of resistance training is essential for protein supplementation to improve muscle strength": with training, strength improved by 2.01% (95% CI 1.09–2.93); without training the effect was just 0.13% (95% CI −1.53 to 1.79) — practically nothing.
The same analysis found a 0.72% (95% CI 0.40–1.04) increase in strength per additional 0.1 g/kg body weight per day, up to about 1.5 g per kilogram of body weight per day, "but no further gains were observed thereafter." There is a ceiling — and spending above it buys nothing.
How much do you actually need? Minimum versus target
The established dietary recommendation is 0.8 g per kilogram of body weight per day. Harvard Health lays out the arithmetic: "140 pounds is 64 kg; multiplying this by 0.8 equals 51" grams a day, and estimates that "for an active adult, about 10% of calories should come from protein."
But it is important to understand what kind of number this is: a floor that prevents deficiency, not an optimum for building or preserving muscle as you age. That is why specialist recommendations run higher: 1.2–1.6 g/kg for older adults, and 1.5 g/kg as the saturation point in the 2022 analysis.
In the other direction, Harvard also sets a ceiling: for the average healthy adult, "no more than 2 gm/kg of ideal body weight; that would be about 125 grams/day for a 140-pound person," with a caution about a higher incidence of kidney stones at excessive intakes. And the core advice it closes with: focus "on the type of protein in your diet rather than the amount."
The whole package: what comes with the protein?
Protein never arrives alone. It arrives inside a "package" of fats, fibre, minerals and vitamins — and that package is what long-term health studies actually track.
Harvard Health summarises the comparison: animal products "contain some of the highest amounts" of protein, but "many sources also include high levels of saturated fat and cholesterol," whereas "plant proteins might be a healthier choice since they also include essential vitamins, minerals, and other micronutrients."
On health outcomes, two very large studies point the same general direction:
- The Nurses' Health Study and Health Professionals Follow-up Study (published in JAMA Internal Medicine, 2016): more than 170,000 participants, more than 3.5 million person-years of follow-up, and more than 36,000 documented deaths. High consumption of animal protein was weakly associated with an increased rate of death, while high consumption of plant protein was associated with a lower mortality rate.
- The NIH-AARP Diet and Health Study (2020): over 400,000 participants across a 16-year follow-up. Participants "who replaced three percent of dietary energy intake from animal protein with an equal amount of plant protein were ten percent less likely to die from any cause over the 16-year follow up."
A necessary methodological caveat: these are observational studies showing association, not causation, and they do not mean animal protein is "harmful." The honest reading is that the signal relates to the accompanying package — processed meat in particular — more than to protein itself. The practical message is simple and actionable: do not eliminate, diversify and partially substitute. Replacing 3% of energy is, in reality, a small change.
What do the Saudi numbers say?
The local picture points to a gap in plant protein sources specifically. In the Saudi Health Interview Survey, published in Public Health Nutrition and covering 10,735 individuals (5,253 men and 5,482 women) aged 15 and over, daily averages were 44.2 g of red meat but only 10.9 g of nuts, and only "31.4% for nuts and 44.7% for fish" met the dietary recommendations.
In a more recent study published in Frontiers in Public Health in 2026 covering 398 young Saudi adults aged 18–25, median plant protein consumption was 14 portions per week (IQR 7–24) against 28 portions per week (IQR 21–35) for animal protein. Only 21.4% of participants reached a high consumption frequency, and 43.2% reported being unfamiliar with the concept of sustainable healthy diets. Higher plant protein consumption was associated with a lower mean body mass index (23.19 ± 6.58 vs 24.57 ± 7.02 kg/m²).
The local conclusion is not "eat less meat." It is that the missing side of the Saudi plate is protein-rich plants — nuts, seeds and legumes — and that is the easier side to adjust.
A five-step practical plan
- Calculate your floor, then raise it deliberately. Multiply your weight in kilograms by 0.8 to find the minimum. If you do resistance training or are over 60, discuss raising the target toward 1.2–1.6 g/kg with a qualified professional.
- Distribute rather than stockpile. Put protein in every main meal instead of concentrating it at dinner. For older adults specifically, aim for roughly 30 g per meal.
- Vary your plant sources across the day, not within the meal. Nuts at one meal, seeds at another, legumes or soy at a third. No "combining" on the same plate is required.
- Move your muscles. Without resistance training, extra protein does not build muscle — the 2022 analysis showed this clearly. Protein is the building material; training is the build order.
- Read the package, not the number. Look at what accompanies the protein: fibre, healthy fats and micronutrients, or added sugar, saturated fat and high sodium? (For more detail, see our guide on how to read a nutrition label.)
Four common misconceptions
1. "Plant protein is incomplete and won't do on its own." Inaccurate. Plant foods contain all the essential amino acids, but in differing amounts and with lower digestibility. The answer is variety and quantity, not wholesale replacement with animal protein.
2. "I must pair rice and beans in the same meal." A rule science has moved past. Balance across the day is sufficient, as MedlinePlus states explicitly.
3. "More protein always means more muscle." There is a ceiling. Strength gains saturated at roughly 1.5 g/kg per day in the 2022 analysis, with no further gains beyond it. And excess has a cost — Harvard notes a higher incidence of kidney stones.
4. "Powdered protein beats food." Not necessarily. Powder delivers quantity and convenience; whole food delivers the whole package. And in that same meta-analysis, supplementation without training made almost no difference.
Who should be careful?
This article is general education and is not a substitute for individual medical advice. Take particular care if you are:
- Living with kidney disease or reduced kidney function: the amount and type of protein is a medical decision made individually with your doctor or dietitian, and there is no single number that fits everyone. (We covered this in more depth in our article on diabetic kidney disease.)
- Allergic or intolerant: nuts, soy and dairy are among the most common allergens. Do not introduce a new source if you have an allergy history without checking first.
- Pregnant, breastfeeding, or growing: requirements differ substantially and need specialist follow-up.
- Following a fully plant-based pattern: monitor vitamin B12, iron and zinc with a professional, since the issue extends beyond protein.
And consult your doctor before any substantial change in protein intake if you take chronic medication or have any existing health condition. 🩺
Where does Bakery 8 stand in all this?
No bread is a substitute for protein. We say it plainly, because that is simply not the job bread does in any diet. What can be said honestly is that the starting point differs: the products of Bakery 8 / مخبز ثمانية in Riyadh, Saudi Arabia are built on almond flour instead of refined flour — and wheat, as you saw in the DIAAS figures, sits at 45 in the lowest band of protein quality. Swapping the base of your baked goods for a nut-derived one is an improvement in a better direction, not a magic fix.
If you want your daily plate to work for you on protein, build the meal around the protein source and then choose its companions intelligently:
- Samoli and cloud bread — a sugar-free, gluten-free base for a sandwich carrying eggs, cheese or chicken, instead of a wheat-based bread.
- Keto granola — a base of nuts and seeds, precisely the food category the Saudi survey found lacking on the local plate.
- Crackers and manakish — an alternative to a snack that is usually built on refined flour.
The core idea: we handle the starchy side of the plate so that more room is left for your protein and fibre. Protein stays your responsibility — from eggs, yoghurt, fish, poultry, nuts, seeds and legumes.
Frequently asked questions
Is plant protein really inferior to animal protein?
Not "inferior" in any absolute sense, but usually less efficient on the two measures of digestibility and amino acid composition. Yet the spread within the plant world is large: soy scores 84–89 on DIAAS, within the good-quality band, while wheat scores 45. The practical upshot is that you need a larger quantity and wider variety of plant sources, not that you should exclude them.
Do I have to combine plant proteins at every meal?
No. MedlinePlus states explicitly that "we no longer worry about pairing proteins… at a single meal." What matters is that your diet is varied across the day and meets your energy needs. What remains true is that relying on a single plant food alone will not be adequate.
How many grams of protein do I need per day?
The recommended minimum is 0.8 g per kilogram of body weight — around 51 g for a 64 kg person. But that is a floor to prevent deficiency, not an optimal target: recommendations for older adults run 1.2–1.6 g/kg, and strength gains saturated around 1.5 g/kg. Set your own number with a professional based on your age, activity and health status.
Are nuts enough as a protein source?
Nuts and seeds are a good source of plant protein and of an accompanying package of healthy fats, fibre and minerals, but their protein density is lower than legumes, soy and animal foods. Treat them as part of the variety rather than the sole source — particularly given that the Saudi survey found average nut intake at just 10.9 g per day.
Are protein supplements necessary?
Not for most people. A meta-analysis of 82 studies and 3,940 participants found that protein supplementation without resistance training made almost no difference to strength (0.13%). A supplement is a convenience tool for closing a quantity gap, not a replacement for training or for whole food.
Is protein intake adequate on a keto diet?
Low-carbohydrate patterns are usually adequate or higher in protein, because their staple foods are protein-rich to begin with. The point that needs attention is plant variety: nuts, seeds, soy and legumes within your carbohydrate limits, because they bring the fibre and micronutrients that can be short in a pattern built on animal foods alone.
Conclusion
The number on the label measures quantity, not quality. Real quality is digestibility multiplied by amino acid composition — which is why the world moved from PDCAAS to DIAAS. Plant protein is not "incomplete," but it needs a larger quantity and wider variety, and it does not need to be combined within a single meal. The dose per meal matters as much as the daily total, and older adults need more. Most importantly: protein builds no muscle without training, and it never works in isolation from the package it arrives in.
Start with one step today: add a protein-rich plant source to a meal you have been overlooking. 🌿 And if you want a sugar-free, gluten-free base to build that plate on, browse the Bakery 8 store — healthy and delicious.
References
- MedlinePlus, U.S. National Library of Medicine — Amino acids (Medical Encyclopedia).
- Academy of Nutrition and Dietetics — Position Paper: Vegetarian Dietary Patterns for Adults (2025).
- Mathai JK, Liu Y, Stein HH — "Values for digestible indispensable amino acid scores (DIAAS) for some dairy and plant proteins may better describe protein quality than values calculated using the concept for protein digestibility-corrected amino acid scores (PDCAAS)," British Journal of Nutrition, 2017;117(4):490–499.
- FAO — Dietary protein quality evaluation in human nutrition: Report of an FAO Expert Consultation (2013).
- Frontiers in Nutrition (2024) — "Impacts of protein quantity and distribution on body composition."
- Tagawa R, et al. — "Synergistic effect of increased total protein intake and strength training on muscle strength," Sports Medicine – Open, 2022.
- Harvard Health Publishing — "When it comes to protein, how much is too much?"
- Harvard Health Publishing — "Ask the doctor: Best protein — animals or plants?"
- Song M, et al. — "Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality," JAMA Internal Medicine, 2016.
- Division of Cancer Epidemiology & Genetics, U.S. National Cancer Institute — NIH-AARP Diet and Health Study: plant and animal protein and mortality (2020).
- Diet in Saudi Arabia: findings from a nationally representative survey (Saudi Health Interview Survey), Public Health Nutrition.
- Al-Otaibi HH, Al-Hashim S — "Plant-based protein consumption patterns among Saudi Generation Z," Frontiers in Public Health, 2026.
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