Quality Protein Sources: DIAAS, Vegan Options, and Combining Them

Not all protein is equal. What actually matters is the essential amino acid profile, true digestibility (now measured with the DIAAS index, which has replaced the old PDCAAS), and how much leucine each serving provides — the amino acid that triggers muscle protein synthesis. This guide covers the most efficient sources per gram and per euro, what recent evidence says about combining plant proteins, and which tools help you hit your daily target without overcomplicating things.

What makes a protein 'high quality': DIAAS and the leucine threshold

DIAAS (Digestible Indispensable Amino Acid Score) is the current standard recommended by the FAO for scoring proteins. It compares a food's most limiting essential amino acid against a reference pattern and corrects for true ileal digestibility, not fecal digestibility as PDCAAS did. A DIAAS of 1.00 or higher indicates 'excellent quality' protein; between 0.75 and 0.99 is 'good quality.'

By this metric, whole eggs score around 1.13, chicken 1.08, and isolated whey protein exceeds 1.00. Most whole legumes fall between 0.5 and 0.7 because they're low in sulfur-containing amino acids (methionine/cysteine), and grains fall between 0.4 and 0.6 due to their lysine deficit. Isolated soy and pea protein stand out among plant sources, approaching 0.9-1.0.

The other relevant variable is the leucine threshold. A 2024 review confirms that you need between 2.5 and 3 g of leucine per meal to maximize muscle protein synthesis, and that this anabolic response lasts 2 to 2.5 hours. The more recent nuance is that total essential amino acid content and digestion speed also matter, not just isolated leucine: that's why a generous serving of legumes can approach the effect of a smaller portion of meat, even though its individual profile is worse.

The best animal sources per gram and per euro

Whey remains, by far, the cheapest option per gram of absorbed protein and has the most complete amino acid profile after eggs. It doesn't replace whole food as a source of micronutrients, but it's the most efficient tool when budget or cooking time is limited.

Powerful plant-based sources

• Firm tofu: 12-15 g/100 g, relatively complete profile thanks to soy.
• Tempeh: 19 g/100 g and higher bioavailability than tofu due to fermentation, which reduces antinutrients.
• Rehydrated textured soy protein: 12 g/100 g, very cheap and versatile for bolognese-style dishes.
• Edamame: 11 g/100 g, and also provides fiber and micronutrients that isolated proteins lack.
• Seitan: up to 25 g/100 g, but very low in lysine; always pair it with legumes or dairy.
• Legumes + grains in the same diet (not necessarily on the same plate): lentils, chickpeas, or beans alongside rice, bread, or oats complete the amino acid profile over the course of the day.
• Hemp seeds and pumpkin seeds: 30 g provides 8-10 g of protein plus healthy fats, useful as an add-on in salads or yogurt.

Do you need to combine proteins in the same meal? What the evidence says

The idea that legumes and grains need to be eaten together on the same plate to 'complete' the protein is a 1970s simplification that current evidence no longer supports. The body maintains a circulating amino acid pool for several hours, so a lysine-rich meal (legumes) at lunch and a methionine-rich one (rice, bread) in the evening complement each other just as well as if they were on the same plate.

The exception is people on a very low calorie intake, older adults with reduced anabolic efficiency, or those eating very few protein sources per day. In those cases, it's worth making sure each individual meal has enough quantity and variety. For everyone else, what matters is total daily protein and each limiting amino acid, not exact timing within a single meal.

Vegan diets: how to reach your 1.6-2.2 g/kg per day

Hitting 1.6 to 2.2 g/kg on a vegan diet is perfectly doable, but it requires more planning than on an omnivorous diet. The usual strategy combines tofu, tempeh, seitan, legumes, textured soy protein, and, if the food volume becomes uncomfortable, a plant-based protein supplement (pea, rice, or a blend of both, which matches whey's amino acid profile).

Since the average digestibility of plant proteins is somewhat lower than animal proteins, a reasonable safety margin is adding 10-20% to the target calculated with any standard formula. Spread protein across 3-4 meals of at least 25-30 g each, and don't rely on a single source: rotating legumes, soy, and nuts reduces the risk of falling short on any specific amino acid over the course of the week.

Tools to hit your protein grams every day without fail

The most common mistake when calculating protein isn't in the formula, it's on the scale: weighing chicken after cooking instead of raw can skew the calculation by 20-25%, because water evaporates during cooking. A kitchen scale with a tare function, 1 g precision, and a capacity of at least 5 kg solves this in seconds and lets you weigh several ingredients in the same container.

If cooking every day is what trips you up, batch cooking solves the problem at its root: cooking 3-4 meals on Sunday with the protein already calculated keeps you from ordering takeout when you're short on time. Look for glass containers with lids safe for the microwave and fridge, which last for years without staining or absorbing odors.

If you use protein powder, a shaker with an internal mesh or ball prevents the clumps a plain cup and spoon leave behind. A 600 ml size leaves room to mix with water or milk without overflowing when you shake it.

Protein and performance: does adding creatine make sense?

Creatine isn't a protein source, but it's the most studied supplement for turning the protein you eat into more strength and more muscle mass. The ISSN's position remains clear: 3-5 g of creatine monohydrate daily, with no need for a loading phase, improves performance in short, intense efforts and amplifies the response to a well-designed strength program.

Other nutrients to watch when you raise animal or plant protein intake

When you increase intake of chicken, turkey, or egg whites to save calories, it's easy to unknowingly cut back on oily fish, the main source of omega-3 (EPA and DHA). If you don't eat salmon, mackerel, or sardines at least 2-3 times a week, a triglyceride-form supplement helps cover that intake without depending on the variability of your weekly menu.

What to choose based on your situation

Common mistakes when choosing protein sources

• Trusting the 'high in protein' label without checking total grams per serving: many ultra-processed products inflate the claim with small portions.
• Ignoring the cost per gram of absorbed protein: a premium steak can cost 3-4 times more than chicken or canned tuna for the same protein payoff.
• Weighing food after cooking instead of raw, which skews the macro calculation by 15% to 25% depending on the cooking method.
• Thinking legumes and grains must be combined on the same plate: it's enough for both to show up in the day's diet.
• Overdoing the supplement and neglecting whole food, which provides fiber, vitamins, and minerals that powder doesn't.
• On vegan diets, relying on a single source (only seitan or only textured soy) instead of rotating several throughout the week.

What to buy (and what not to): a kit for hitting your protein target

You don't need to buy anything to hit your protein target if you cook smart: chicken, eggs, canned tuna, legumes, and dairy cover almost anyone. Where gear does make a real difference is in weekly organization and in not leaving nutritional gaps as you raise lean protein intake.

Frequently asked questions

How much protein do I really need per day?

It depends on your goal: 0.8-1.2 g/kg if you're sedentary, 1.6-2.2 g/kg if you train for strength to gain or maintain muscle, and up to 2.2-2.4 g/kg during aggressive calorie deficits to protect lean mass. Use PesaFit's protein calculator to fine-tune the number based on your weight and goal.

Do I have to combine legumes and grains in the same meal?

No. Current evidence shows the body uses an available amino acid pool over several hours, so it's enough for both groups to show up in your diet that day. The only exception is diets that are very restrictive in calories or food variety.

Is protein powder as good as whole food?

In terms of amino acids and digestibility, quality whey or plant protein matches or exceeds many solid foods. What they don't provide is the fiber, vitamins, and minerals found in whole food, so they work better as a complement than as a regular replacement.

Does excess protein damage your kidneys?

In healthy people, available studies show no kidney damage with intakes of up to 2.5-3 g/kg per day sustained over time. If you have pre-existing kidney disease, talk to your doctor before raising intake above general recommendations.

What's the best vegan protein powder?

A pea and rice blend is the most balanced option: pea provides the lysine rice lacks, and rice provides the sulfur-containing amino acids pea lacks. The result comes close to whey's profile.

When is it best to take protein, before or after training?

The so-called 'anabolic window' is much wider than previously thought: what determines the outcome is your daily total and spreading it across 3-4 servings of at least 0.3-0.4 g/kg, not the exact minute you drink your shake.

What happens if I don't hit my protein grams one day?

Nothing serious. What determines results in the medium term is the weekly average, not hitting the exact number every single day. If you fall short one day, just make up for it over the following days without obsessing over that single data point.