Do lentils and quinoa make a complete protein?

November 26, 2025 •

3 min read

Contrary to a decades-old myth, you don't need to combine complementary proteins in a single meal to get all essential amino acids. However, people still wonder: do lentils and quinoa make a complete protein, and what are their individual nutritional profiles? This article explores the science behind plant-based proteins and provides clarity for your dietary choices.

Quick Summary

Lentils and quinoa together form a complementary protein pairing that provides all essential amino acids. Although quinoa is often considered a complete protein, combining it with lentils—rich in the amino acid lysine—creates a more robust amino acid profile. You do not need to combine them in the same meal, but they offer a powerful and nutritious duo for plant-based diets.

Key Points

Essential Amino Acids: To form a complete protein, your body needs nine essential amino acids, which must be consumed through your diet.
Lentils are 'Incomplete': Lentils are not a complete protein on their own, as they are low in the amino acids methionine and cysteine.
Quinoa is 'Nearly Complete': Quinoa contains all nine essential amino acids but some experts consider it 'nearly complete' due to lower amounts of certain amino acids.
Lentils + Quinoa = Complementary Protein: Combining lentils (high in lysine) and quinoa (containing methionine) creates a meal with a more robust and complete amino acid profile.
The Combining Myth is Busted: You do not need to combine complementary proteins in the same meal; your body stores amino acids and uses them as needed throughout the day.
Focus on Variety: A varied diet featuring a range of plant-based protein sources like soy, nuts, and seeds ensures you get all the essential amino acids you need.

Understanding Complete vs. Incomplete Proteins

Proteins are fundamental to life, composed of smaller organic compounds called amino acids. The human body requires 20 different amino acids to function, though it can produce 11 of them on its own. The remaining nine, known as "essential amino acids," must be obtained through food. A "complete protein" is a food source that contains all nine essential amino acids in sufficient quantities to meet the body's needs.

The Role of Essential Amino Acids

Each essential amino acid plays a vital role in bodily functions. Animal products typically contain all nine essential amino acids, making them complete proteins. Many plant foods, however, may be lower in or missing one or more essential amino acids, leading to the historical misconception that they were "incomplete".

The Nutritional Profile of Lentils

Lentils are a nutrient-dense legume rich in protein, fiber, vitamins, and minerals. While they are high in the essential amino acid lysine, they are lower in methionine and cysteine, meaning they are not a complete protein on their own. This is why traditional diets often pair lentils with grains that are higher in methionine.

Is Quinoa a Complete Protein on Its Own?

Quinoa, a pseudocereal often treated as a grain, is frequently labeled a complete protein because it contains all nine essential amino acids. A single serving of cooked quinoa offers about 8 grams of protein. However, some experts suggest the levels of certain amino acids, like lysine, might be too low to be officially considered complete, preferring the term "nearly complete". Regardless, quinoa remains a valuable protein source.

The Power of Complementary Pairing: Lentils and Quinoa

Combining lentils and quinoa creates a complementary protein source. Lentils provide ample lysine to supplement quinoa, while quinoa supplies methionine, which lentils lack. This pairing offers a balanced and complete protein profile.

Practical Combinations Beyond Lentils and Quinoa

While not strictly necessary for every meal, combining complementary proteins is easy. Other beneficial pairings include:

Brown rice and black beans
Hummus and whole-grain pita bread
Peanut butter on whole-grain toast
Salads with nuts, seeds, and legumes

Debunking the Protein Combining Myth

The belief that plant proteins must be combined in a single meal to be effective is outdated. This idea, popular in the 1970s, has been refuted by its originator and nutritional experts.

The Body's Amino Acid Pool

Your body doesn't need all essential amino acids at once. It maintains a pool of amino acids, which it uses throughout the day to build complete proteins. Consuming a varied diet with sufficient calories allows your body to effectively use amino acids from different plant foods, whether eaten together or separately.

Lentils vs. Quinoa: A Nutritional Comparison


Nutrient (per half-cup, cooked)	Lentils (approx.)	Quinoa (approx.)
Calories	115 kcal	111 kcal
Protein	9 grams	4 grams
Fiber	8 grams	2.5 grams
Fat	0.36 grams	1.75 grams
Carbohydrates	20 grams	20 grams
Nutritional Highlights	Excellent source of iron, potassium, and magnesium. Very high in fiber.	Good source of iron, magnesium, and healthy omega fatty acids. Complete protein profile.

How to Build a Complete Plant-Based Diet

Getting all essential amino acids on a plant-based diet is achieved through variety, not strict food combining. Including a diverse range of plant protein sources daily will naturally provide a complete amino acid profile.

Examples of plant-based complete protein sources include:

Soy Products: Tofu, tempeh, and edamame
Certain Seeds: Hemp seeds and chia seeds
Nutritional Yeast: Often fortified with B vitamins
Ezekiel Bread: Made from sprouted grains and legumes

Conclusion

Lentils and quinoa are both valuable plant-based protein sources, each with distinct amino acid profiles. Lentils are high in lysine but lower in methionine, while quinoa contains all essential amino acids but in potentially lower quantities of some. Combining them creates a complementary protein with a balanced amino acid profile, a practice found in various healthy cuisines. However, due to the body's ability to utilize an amino acid pool, these foods do not need to be eaten together in the same meal for the body to form complete proteins. A diverse intake of plant-based protein foods throughout the day is sufficient for meeting nutritional needs. For more information on vegetarian diet adequacy, consult resources like the Academy of Nutrition and Dietetics position paper.

Frequently Asked Questions

Yes, quinoa is considered a complete protein because it contains all nine essential amino acids. Some experts note that the amounts of certain amino acids are low, but it is still a high-quality plant protein source.

No, lentils are not a complete protein on their own because they contain limited amounts of the sulfur-containing amino acids methionine and cysteine.

No, the body does not require complementary proteins to be consumed at the same meal. As long as you eat a varied diet throughout the day, your body's amino acid pool will combine the necessary amino acids.

Combining lentils and quinoa creates a perfectly balanced amino acid profile, as the lentils provide abundant lysine while the quinoa provides the methionine that lentils lack.

Other complete plant-based proteins include soy products (tofu, tempeh), hemp seeds, chia seeds, pistachios, and nutritional yeast.

Per half-cup, cooked lentils contain approximately 9 grams of protein, while cooked quinoa contains about 4 grams.

Yes, a well-planned vegan diet can provide all the protein and amino acids needed for good health. Focusing on a variety of whole plant-based foods, including legumes, grains, nuts, and seeds, is key.