Amaranth is a complete protein. It contains all nine essential amino acids your body cannot make on its own, and in quantities that meet or come close to the benchmarks set by the World Health Organization. This puts amaranth in rare company among plant foods, alongside quinoa and soy as reliable sources of complete protein from a single ingredient.
What Makes a Protein “Complete”
A complete protein provides all nine essential amino acids in meaningful amounts: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Most plant foods fall short in at least one of these. Grains like wheat and rice are low in lysine. Legumes like beans and lentils are low in methionine. Your body needs all nine to build and repair tissue, so a food missing one becomes a bottleneck.
Amaranth sidesteps this problem. Its amino acid profile, measured in grams per 100 grams of protein, shows solid levels across the board: lysine at 10.1, leucine at 7.85, histidine at 6.83, tryptophan at 5.51, methionine at 4.69, phenylalanine at 3.80, valine at 3.11, threonine at 3.05, and isoleucine at 2.87. That lysine number is especially notable. Most grains contain so little lysine that it becomes their limiting amino acid. Amaranth delivers roughly 4.9 to 6.1 grams of lysine per 100 grams of protein, far more than wheat, corn, or rice.
How Amaranth Scores on Protein Quality Tests
The standard tool for measuring protein quality is the PDCAAS (Protein Digestibility-Corrected Amino Acid Score), which accounts for both amino acid content and how well your body can actually digest and use the protein. A perfect score is 100.
Raw amaranth scores impressively. In a study testing three varieties (white, red, and brown), raw amaranth hit 100 for lysine, sulfur amino acids (methionine and cysteine), and aromatic amino acids (phenylalanine and tyrosine) in the white and red varieties. Leucine scored between 85 and 98 depending on variety. The protein’s overall composition closely aligns with the amino acid recommendations set by the FAO and WHO, meaning it delivers nutrients in roughly the proportions your body actually needs.
Protein digestibility sits around 90%, which is high for a plant food. For comparison, many legumes have digestibility in the 70 to 80% range before cooking adjustments.
Where Amaranth Outperforms Other Grains
Amaranth isn’t technically a grain. It’s a pseudocereal, like quinoa and buckwheat, meaning it’s a seed that gets used like a grain in cooking. But comparing it to both true grains and its pseudocereal relatives is useful.
Uncooked amaranth contains about 26.2 grams of protein per 100 grams, compared to 24 grams for quinoa and 15.1 grams for buckwheat flour. A single cup of cooked amaranth provides roughly 17% of your Daily Value for protein. Beyond total protein, amaranth is particularly rich in lysine and methionine, the two amino acids that are hardest to get from plant sources. Lysine is the weak link in cereals, and methionine is the weak link in legumes. Amaranth covers both, which makes it a strong complement to nearly any plant-based diet.
How Cooking Affects Protein Quality
Not all preparation methods treat amaranth’s protein equally. Heat can damage certain amino acids, particularly tryptophan and the sulfur-containing amino acids methionine and cysteine. Popping amaranth (heating it until it puffs like tiny popcorn) causes the most significant losses. In popped amaranth, PDCAAS scores for lysine dropped to 64 in white and brown varieties and 71 in red. Leucine scores also fell, landing between 77 and 85.
Boiling and steaming are gentler on the amino acid profile. Fermentation actually preserves or improves protein quality. Fermented amaranth scored 100 for lysine, sulfur amino acids, and aromatic amino acids in white varieties, matching or exceeding the raw grain.
Sprouting (also called malting) may be the most beneficial preparation method. Germination triggers enzymes that break stored proteins into amino acids and small peptides, making them easier to absorb. Studies show that almost all amino acids in amaranth increase in retention after sprouting. If you’re trying to maximize the protein you get from amaranth, sprouting the seeds before cooking or eating them gives you the best results.
Practical Considerations for Plant-Based Diets
Amaranth being a complete protein doesn’t mean you need to rely on it as your sole protein source. One cup of cooked amaranth delivers a meaningful contribution, but at 17% of your Daily Value, you’ll still want variety. What amaranth does exceptionally well is fill the gaps left by other plant foods. Pair it with beans or lentils, and you’ve covered every amino acid generously from both directions. Eat it alongside rice or oats, and amaranth’s high lysine compensates for the grains’ weakness.
Amaranth also carries 14 to 19% protein by weight in its raw form, which is higher than most true cereal grains. You can cook it as a porridge, pop it for a crunchy topping, stir the flour into baked goods, or sprout the seeds and add them to salads. Each method delivers complete protein, though the amino acid balance shifts slightly depending on how much heat is involved. For the best nutritional return, favor boiling, steaming, sprouting, or fermenting over dry-heat popping.