Which grain is considered a complete protein?

November 2, 2025 •

3 min read

Just a few plant-based foods, including certain pseudocereals often mistaken for grains, contain all nine essential amino acids. This article answers the question, "Which grain is considered a complete protein?" and explores the best options for enhancing your diet.

Quick Summary

This article examines which pseudocereals are complete proteins, covering quinoa, amaranth, and buckwheat. It also explains how to combine common incomplete grains with legumes to create a full amino acid profile.

Key Points

Complete vs. Incomplete Protein: A complete protein contains all nine essential amino acids, which the body cannot produce on its own.
Quinoa is a Complete Protein: The pseudocereal quinoa contains all nine essential amino acids, making it a complete protein source.
Other Complete Pseudocereals: Amaranth and buckwheat are also complete protein pseudocereals that are often grouped with grains.
Complementary Protein Combining: Common grains like rice and wheat are incomplete, but can be paired with legumes like beans or peanuts to form a complete protein.
Variety is Key: Eating a variety of protein sources, even if they are incomplete individually, will ensure your body gets all essential amino acids throughout the day.
Plant-Based Options Abound: Vegetarians and vegans have numerous complete or combinable protein sources beyond just grains and pseudocereals, including soy products, hemp seeds, and chia seeds.

Understanding Complete vs. Incomplete Proteins

To understand which grain is considered a complete protein, it's crucial to first grasp the difference between complete and incomplete protein sources. Protein is made up of smaller units called amino acids. There are 20 different amino acids, and your body can produce most of them. However, nine of these are considered 'essential' because they cannot be synthesized by the human body and must be obtained through diet.

Complete proteins: These are food sources that contain all nine of the essential amino acids in sufficient quantities. Most animal products, such as meat, fish, eggs, and dairy, fall into this category.
Incomplete proteins: These foods are typically low in one or more of the essential amino acids. The vast majority of plant-based protein sources, including most cereals and true grains like rice and wheat, are incomplete on their own.

For those on a vegetarian or vegan diet, consuming a variety of plant-based foods throughout the day naturally provides all the essential amino acids. The body can combine these amino acids from different meals to form a complete protein.

The Top Pseudocereal Complete Proteins

While technically not true cereal grains, these plant-based options are cooked and eaten like grains and are notable for their complete protein profiles.

Quinoa

Quinoa is a popular pseudocereal praised as a complete protein source. Originating from the Andean region, it has a mild, nutty flavor and a slightly chewy texture. One cup of cooked quinoa offers about 8 grams of protein and is also rich in other essential nutrients like magnesium, iron, zinc, and fiber. Its status as a complete protein makes it an excellent foundation for plant-based meals, serving as a substitute for rice or couscous.

Amaranth

Like quinoa, amaranth is a pseudocereal that is a complete source of protein. Once a staple of Aztec and Incan cultures, amaranth can be cooked into a porridge-like consistency, added to salads for texture, or popped like popcorn. A cooked cup provides approximately 9 grams of protein and is also an outstanding source of manganese, magnesium, and phosphorus.

Buckwheat

Despite its name, buckwheat is not related to wheat and is a gluten-free pseudocereal. It is also considered a complete protein source, though with slightly less protein per serving than quinoa or amaranth. Buckwheat groats can be used in place of oats for breakfast, and its flour is a popular ingredient for pancakes and soba noodles. Besides protein, buckwheat provides a wealth of minerals, including phosphorus, manganese, and copper.

Creating Complete Proteins with Common Grains

For common grains that are incomplete proteins, the key is to pair them with complementary foods. You do not need to consume complementary proteins in the same meal, but including a variety of sources throughout the day is a good strategy for nutritional balance.

Rice and Beans: This is a classic example of complementary protein pairing. Rice is low in the essential amino acid lysine, while beans are rich in it but lack methionine. Together, they form a complete protein.
Peanut Butter on Whole-Grain Toast: Whole-grain bread is low in lysine, which legumes like peanuts provide in abundance.
Hummus and Pita Bread: This combination pairs the chickpea-based hummus with the whole-wheat pita bread to create a complete protein.

Comparing Complete Grain/Pseudocereal Protein Sources


Feature	Quinoa	Amaranth	Buckwheat
Protein Content (per cooked cup)	~8 grams	~9 grams	~6 grams
Essential Amino Acids	All nine, though amounts vary	All nine, well-balanced	All nine, well-balanced
Gluten-Free	Yes	Yes	Yes
Texture	Mild, nutty, and slightly chewy	Nutty, earthy, and crunchy	Nutty, earthy
Best Used For	Salads, side dishes, bowls, breakfast porridge	Porridge, salads, texture in granola	Soba noodles, pancakes, oatmeal replacement

Conclusion

While most common grains are incomplete proteins, several pseudocereals provide a full spectrum of essential amino acids. Quinoa, amaranth, and buckwheat are all excellent choices for anyone seeking a naturally complete plant-based protein. For other grains like rice, creative food pairings with legumes can easily create a complete protein profile, ensuring your body receives all the necessary building blocks for health. Embracing a diverse and varied diet is the most effective strategy for meeting your daily protein requirements, regardless of whether you follow a plant-based or omnivorous diet.

For more in-depth nutritional information on plant-based diets, visit Healthline's guide to complete proteins.

Frequently Asked Questions

Yes, quinoa is considered a complete protein because it contains all nine essential amino acids. While some suggest certain amino acids are present in lower amounts, it is still a robust plant-based complete protein.

True grains, like wheat or rice, come from grasses. Pseudocereals, like quinoa, amaranth, and buckwheat, are seeds from other types of plants that are cooked and eaten like grains.

No, the body stores a 'pool' of amino acids that it can draw from to create complete proteins throughout the day. The old advice about combining proteins in a single meal is now considered outdated.

A classic example is rice and beans. Rice is low in the amino acid lysine, while beans are rich in it. Combined, they provide all essential amino acids.

Other complete protein pseudocereals include amaranth and buckwheat. Both provide a full amino acid profile and can be used in similar ways to quinoa.

Yes, several other plant-based foods are complete proteins, including soy products (tofu, tempeh), hemp seeds, and chia seeds.

Incorporate a variety of sources like quinoa, buckwheat, and amaranth into meals. For other grains, simply pair them with legumes, nuts, or seeds, such as a peanut butter sandwich on whole-wheat bread.