The guide

What is a complete protein, and which foods have one?

By GyroscopeUpdated November 15, 20266 sources

Every food with protein has all nine essential amino acids. What differs is how much of each. Against the amounts adults need, eggs, dairy, meat and fish clear every line with room to spare. Soy, black beans and chickpeas meet them too. Grains and nuts run short on one amino acid, lysine, and that’s the gap the old “incomplete protein” warning was about.

Where “incomplete protein” came from

You’ve probably heard that plant proteins are incomplete, that only meat, eggs and dairy are complete, and that quinoa is the one plant that made the cut. It’s on the side of quinoa bags for a reason.

Part of that is true. Plant proteins usually carry less of one or two essential amino acids than animal proteins. But “incomplete” makes it sound like something is missing, and nothing is. Every protein in this chart has all nine. Quinoa does meet the adult pattern, just barely, at 101% on leucine. So do black beans and chickpeas, which nobody puts on the label.

The nine amino acids and the yardstick

Your body builds protein from amino acids, and it can make most of them itself. Nine it can’t, so they have to come from food: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Two of them are counted with a partner they can be made into, methionine with cysteine and phenylalanine with tyrosine.

To say whether a food has enough of each, you need a yardstick. The one here is the adult requirement pattern from the 2007 WHO, FAO and UN University report, as FAO amended it in 2013. It’s the amount of each amino acid adults need per gram of protein.

Think of it like a recipe card for bread. If the recipe needs four eggs a loaf and you have eight eggs, you can make two loaves, no matter how much flour you have. The amino acid you run out of first sets how much of the protein you can use for building, and it’s called the limiting amino acid. A food’s amino acid score is that one, as a share of the pattern.

Every food, ranked by its scarcest amino acid

The animal foods all score 100, and so do soy, black beans, chickpeas, hummus, quinoa, oats and chia. Lentils come in at 98, a hair short on methionine and cysteine. Pumpkin seeds (91) and hemp seeds (90) are a little short on lysine. Then the grains and nuts drop off: peanuts 77, white and brown rice 80, peanut butter 68, whole wheat and almonds 60, pasta 50. Every one of them is short on the same amino acid, lysine.

Each food’s nine amino acids

Here’s the full shape for the foods people ask about most. Each bar is one amino acid per gram of that food’s protein, as a share of the adult pattern, and the line is 100%. Orange bars fall under it.

Egg, wholeMeets the pattern

HisIleLeuLysMetPheThrTrpVal

Chicken breastMeets the pattern

HisIleLeuLysMetPheThrTrpVal

Greek yogurt, nonfatMeets the pattern

HisIleLeuLysMetPheThrTrpVal

SalmonMeets the pattern

HisIleLeuLysMetPheThrTrpVal

Soy (tofu, tempeh, edamame)Meets the pattern

HisIleLeuLysMetPheThrTrpVal

Black beansMeets the pattern

HisIleLeuLysMetPheThrTrpVal

Lentils98%, short on methionine and cysteine

HisIleLeuLysMetPheThrTrpVal

ChickpeasMeets the pattern

HisIleLeuLysMetPheThrTrpVal

QuinoaMeets the pattern

HisIleLeuLysMetPheThrTrpVal

OatsMeets the pattern

HisIleLeuLysMetPheThrTrpVal

White rice80%, short on lysine

HisIleLeuLysMetPheThrTrpVal

Whole wheat60%, short on lysine

HisIleLeuLysMetPheThrTrpVal

Pasta50%, short on lysine

HisIleLeuLysMetPheThrTrpVal

Peanut butter68%, short on lysine

HisIleLeuLysMetPheThrTrpVal

Almonds60%, short on lysine

HisIleLeuLysMetPheThrTrpVal

Pumpkin seeds91%, short on lysine

HisIleLeuLysMetPheThrTrpVal

Hemp seeds90%, short on lysine

HisIleLeuLysMetPheThrTrpVal

Chia seedsMeets the pattern

HisIleLeuLysMetPheThrTrpVal

Two patterns stand out. Animal foods and soy sit well over the line almost everywhere. And the plant foods split into two families that cover each other: beans and lentils are rich in lysine and lower in methionine and cysteine, while grains and nuts are the reverse. Black beans carry 69 mg of lysine per gram of protein and white rice 36, against the 45 adults need.

That’s the whole idea behind rice and beans. It also explains a combo that doesn’t work. Peanut butter has 31 mg of lysine per gram of protein and whole wheat 27, so a peanut butter sandwich is short on lysine no matter how thick you spread it. On two slices it scores 64%.

Digestion: the second half of the score

Composition is only what’s in the food. What counts for muscle is what you absorb, and plant proteins come wrapped in fiber and compounds that slow digestion a little. That’s what DIAAS adds, the digestible indispensable amino acid score that FAO recommended in 2013. It measures how much of each amino acid is absorbed by the end of the small intestine, usually in growing pigs, the animal FAO prefers for the test.

In 2020, Laure Herreman and colleagues pooled the published pig data for 17 protein sources and worked out a DIAAS for each.

On this score, casein, pork and egg are excellent, soy and whey are high quality, and pea, oat, hemp, wheat, rice and corn fall below 75. Two limits matter here. They scored against FAO’s pattern for children 6 months to 3 years, which asks for more of every amino acid than the adult pattern, so every number is lower than it would be for an adult. That’s why whey comes out short on histidine. And the authors work at Avebe, a company that sells potato protein, which scored 100.

The same team modeled mixes. Pea alone scored 70 and wheat 48, and at 60 parts pea to 40 parts wheat the mix scored 85, higher than either one. Their conclusion was that the right pairs of plant proteins can reach high quality without any animal protein.

What it means for your day

For most people, completeness takes care of itself. A day with eggs, dairy, meat or fish covers every amino acid many times over, and so does a plant day built on soy, beans and lentils.

It starts to count when one weak food carries most of your protein. In a 2025 review of 43 trials by Reid-McCann and colleagues, soy built as much muscle as milk, while single plant proteins other than soy, like rice or oat protein on their own, built less. A day of toast, pasta, rice and peanut butter has the same problem on a smaller scale.

Variety fixes it. The US guidelines say vegetarians and vegans should “diversify plant protein sources for amino acid balance”, and the trials show the total matters most. You don’t have to pair foods at every meal, but it’s easy to, and our plant combos page shows which pairs work.

How the numbers here are worked out

The amino acids are USDA FoodData Central’s SR Legacy rows, pulled from the FDC API on November 15, 2026, in grams per 100 g with each record’s own protein figure. Each food’s score is its lowest amino acid per gram of protein divided by the adult pattern, capped at 100 the way label scores are. It’s composition only, before digestion.

A few USDA rows didn’t hold up, so they’re left out or swapped:

• Soy foods (tofu, tempeh, edamame) use USDA’s cooked soybean record, because their own rows add up to less than their protein or carry almost no cystine.
• Whole wheat uses the whole-wheat pita record. The whole-wheat bread record has no amino acids, and its toasted twin adds up to only 40% of its protein.
• Cheddar and mozzarella are left out. Their tryptophan equals their methionine and their lysine is about half of milk’s, which looks like a data error.
• Greek yogurt, shrimp, whey and hummus use USDA’s nearest records with amino acids (Chobani plain nonfat, canned shrimp, dried sweet whey and home-prepared hummus), since the records on the rest of this site have none.

DIAAS values are Herreman’s published numbers, never worked out here. We didn’t find an open table of PDCAAS, the older label score, for these foods, so it isn’t shown.