What Vegetable Has All 9 Essential Amino Acids? The Truth About Complete Plant Proteins

November 11, 2025 •

2 min read

While most animal proteins are complete, few individual plant foods contain all nine essential amino acids necessary for human health. The most direct answer to the question of what vegetable has all 9 essential amino acids points to soybeans, a unique and potent source of complete protein in the plant world.

Quick Summary

Soybeans are a complete protein source containing all nine essential amino acids. Other plant-based options like quinoa, hemp seeds, and chia seeds also provide a complete amino acid profile.

Key Points

Soybeans are the primary 'vegetable' containing all nine essential amino acids, making them a complete protein source.
Quinoa, a pseudocereal, is also a complete protein commonly used in plant-based diets.
Other complete plant proteins exist and include buckwheat, hemp seeds, chia seeds, and spirulina.
Most single vegetables are incomplete proteins, lacking one or more essential amino acids.
Combining different plant-based foods throughout the day provides all essential amino acids, even if individual foods are incomplete.
Consuming a varied plant-based diet ensures adequate intake of all essential amino acids without needing strict meal combining.

The Standout: Soybeans as a Complete Protein

When considering a 'vegetable' that provides all essential amino acids, soybeans are the prime example. As a legume, soybeans are a complete protein source, offering all nine essential amino acids. This makes them a fundamental component of many plant-based diets. Soybeans come in various forms, including edamame, tofu, tempeh, soy milk, and soy protein isolates, all retaining their complete protein status.

The Honorary 'Vegetable': Quinoa

Often prepared like a grain or vegetable, quinoa is technically a seed from a plant and stands out as a complete protein source. This pseudocereal is packed with nutrients, including a complete amino acid profile, fiber, magnesium, and iron, making it a versatile and healthy option for various dishes.

Other Notable Complete Plant Protein Sources

Beyond the most common examples, other plant-based foods provide a complete amino acid profile:

Buckwheat: A pseudocereal with a distinctive flavor.
Hemp Seeds: Offer complete protein and beneficial fatty acids.
Chia Seeds: Small seeds that are complete proteins and high in fiber.
Spirulina: A nutrient-dense blue-green alga that is rich in protein.

The Strategy of Complementary Proteins

Most plant foods are incomplete proteins, meaning they lack sufficient levels of one or more essential amino acids. However, combining different plant proteins throughout the day ensures the intake of all essential amino acids. The body maintains a pool of amino acids, so combining doesn't need to occur in a single meal. Pairing grains and legumes, such as rice and beans, or legumes with nuts/seeds, like hummus with pita, are classic examples of complementary protein combinations.

Comparison of Complete Plant Protein Sources


Source	Type	Protein Content (per cup, cooked)	Key Nutrients	Common Use	Contains All 9 EAAs?
Soybeans (Edamame)	Legume	~17 grams (shelled)	Fiber, Folate, Vitamin K	Snack, side dish	Yes
Quinoa	Pseudocereal	~8 grams	Fiber, Magnesium, Iron	Grain bowl base, salad	Yes
Spirulina (powder)	Algae	4-6 grams (per tablespoon)	High protein density, Iron, B vitamins	Smoothies, supplements	Yes

Conclusion: Navigating the Plant Protein Landscape

While soybeans are the primary 'vegetable' known for being a complete protein, other plant-based options like quinoa and various seeds also offer all nine essential amino acids. For individuals following a plant-based diet, obtaining complete protein is achievable through dietary variety. Consuming a range of protein-rich plant foods like legumes, grains, nuts, and seeds throughout the day ensures all essential amino acid needs are met, contributing to a healthy and well-rounded diet. This diverse approach not only covers protein requirements but also provides a broad spectrum of other vital nutrients.

For more detailed nutritional information on dietary guidelines, consult the U.S. Department of Agriculture's FoodData Central. [https://fdc.nal.usda.gov/]

Frequently Asked Questions

Soybeans, which are botanically a legume but culinarily used as a vegetable, are the most prominent complete protein. This includes edamame, tofu, and tempeh.

Quinoa is a pseudocereal, a plant that is not a true cereal grain but is used similarly. It is also a complete protein, containing all nine essential amino acids.

Yes, you can. The 'complete protein at every meal' concept is outdated. The body can store amino acids and combine them over a day from a varied diet to create complete proteins.

Common examples include rice and beans, peanut butter on whole-grain toast, or hummus with pita bread. These pairings provide a full set of essential amino acids.

Most individual green vegetables, including broccoli, are considered incomplete proteins. However, they can contribute to your overall amino acid intake when part of a varied diet.

While some plant proteins may have lower digestibility or lower amounts of certain amino acids compared to animal sources, complete plant proteins like soy and quinoa are still excellent, high-quality sources.

Yes, spirulina is a blue-green algae known for being a potent source of complete protein, containing all the essential amino acids.