Which Vegetables Have the Highest Amino Acids for Complete Plant Protein?

November 1, 2025 •

4 min read

Fact: Soybeans are one of the few plant foods considered a complete protein, containing all nine essential amino acids. Many vegetables also provide crucial amino acids. This article explores which vegetables have the highest amino acids and how to maximize your plant-based protein intake for optimal health.

Quick Summary

Find out which specific vegetables and legumes are a rich source of amino acids. An overview of complete protein plants like soybeans and quinoa is provided, alongside strategies for combining different vegetables to ensure a balanced essential amino acid intake throughout the day.

Key Points

Complete Proteins: Some plant foods like soybeans, quinoa, and amaranth contain all nine essential amino acids.
Soybean Products: Edamame, tofu, and tempeh are excellent sources of high-quality, complete protein for plant-based diets.
Amaranth and Quinoa: These gluten-free pseudocereals offer a complete amino acid profile, with amaranth being especially rich in lysine.
Complementary Proteins: Combining plant foods like legumes (e.g., peas, beans) and grains (e.g., rice) throughout the day ensures a balanced essential amino acid intake.
High-Protein Greens: Leafy greens like spinach, kale, and Brussels sprouts provide a good amount of protein, vitamins, and minerals per calorie.
Varied Diet: Consuming a diverse range of protein-rich plant foods is the most effective strategy to meet all amino acid requirements without needing to pair specific foods in every meal.
Cooking Effects: Some processing methods like overcooking can slightly reduce certain amino acid levels, while others, like fermentation, can increase bioavailability.

Understanding Amino Acids in a Plant-Based Diet

Amino acids are the foundational building blocks of protein, essential for virtually every function in the human body, from building muscle and repairing tissues to producing hormones and neurotransmitters. The human body can synthesize some amino acids, but nine are 'essential' and must be obtained from food. Animal-based foods typically contain all nine, making them complete protein sources. In contrast, most plant-based foods are considered incomplete proteins, lacking one or more essential amino acids. However, by consuming a varied diet of plant foods, you can easily obtain all the necessary amino acids.

Complete Protein Powerhouses from the Plant Kingdom

While many people believe complete proteins only come from meat, several plant sources contain all nine essential amino acids, making them standout options for plant-based diets. These are often technically pseudocereals or legumes rather than what are typically considered 'vegetables,' but are widely grouped with them for nutritional purposes.

Soybeans (Edamame, Tofu, Tempeh): The soybean is a nutritional all-star, providing a complete and high-quality protein. Edamame (immature soybeans) is a delicious, protein-packed snack, while tofu and tempeh, made from processed soybeans, offer versatile, complete protein for meals. Edamame, specifically, contains nearly 18 grams of protein per cooked cup.
Quinoa: This ancient seed is a popular and potent source of complete protein. A cup of cooked quinoa offers about 8 grams of protein and is noted for having higher lysine content than many other grains.
Amaranth: A gluten-free pseudocereal, amaranth is celebrated for its balanced amino acid composition, particularly its rich lysine and tryptophan content, which are often limited in other grains.
Buckwheat: Like quinoa and amaranth, buckwheat is another pseudocereal that provides all the essential amino acids, making it a valuable addition to a complete protein-focused diet.

High-Protein Vegetables (Incomplete Proteins)

Beyond the complete protein sources, many common vegetables are rich in specific amino acids and contribute significantly to overall protein intake. These can be combined with other food groups, like whole grains or legumes, to form a complete protein profile over the course of a day.

Leafy Greens:

Spinach: Cooked spinach provides about 6 grams of protein per cooked cup, along with a rich supply of vitamins and minerals.
Kale: This nutrient-dense leafy green offers nearly 4 grams of protein per cooked cup and is packed with antioxidants.
Brussels Sprouts: A small but mighty vegetable, Brussels sprouts deliver 4 grams of protein per cooked cup and are excellent sources of vitamin C.

Other Vegetables:

Green Peas: A cup of cooked green peas provides about 8 grams of protein, often ranking among the highest protein vegetables.
Mushrooms: These fungi have a unique, meaty flavor and can provide up to 6 grams of protein per cup when cooked.
Asparagus: This popular vegetable contains around 4.3 grams of protein per cooked cup and is also a good source of fiber and vitamins.

How to Combine for a Complete Amino Acid Profile

For those who consume a wide range of plant-based foods, concerns about incomplete protein are often overblown, as the body can store and combine amino acids throughout the day to meet its needs. The key is consuming a variety of protein-rich plant foods. Classic combinations, known as complementary proteins, naturally pair foods with different amino acid profiles.

Legumes + Grains: A classic example is beans and rice. Legumes like beans and lentils are rich in lysine but low in methionine and tryptophan, while grains are typically low in lysine but higher in sulfur-containing amino acids. Paired together, they form a complete protein.
Legumes + Nuts/Seeds: Pairing lentils or chickpeas with seeds, such as in a hummus and pita combination, provides a well-rounded amino acid intake.

Amino Acid Profile Comparison of Top Plant Sources


Food Source	Protein (g/100g, approx.)	Key Strengths	Limiting Amino Acids (if any)	Notes
Soybeans	36g (dry weight)	Complete, well-balanced profile	Methionine & Cysteine	Versatile for tofu, tempeh, edamame
Amaranth	13g (dry weight)	Complete, high in Lysine	None	Pseudocereal, gluten-free
Spinach	2.9g (raw)	Good source of many amino acids	Methionine & Cysteine	Nutrient-dense leafy green
Quinoa	14g (dry weight)	Complete, high in Lysine	None	Pseudocereal, gluten-free
Green Peas	8g (cooked cup)	High protein count for a veggie	None specifically mentioned	Versatile in many dishes

Other Notable Plant-Based Sources

While not strictly vegetables, other plant foods are excellent sources of amino acids and complement a vegetable-rich diet perfectly. Seeds and nuts, for example, provide a good source of protein and healthy fats. Hemp, chia, and flax seeds are notable for their comprehensive amino acid content. Legumes like lentils, black beans, and chickpeas are also high in protein and are staples in many diets for good reason.

Conclusion

While soybeans, amaranth, and quinoa stand out as complete protein sources, a broad range of vegetables offers a diverse amino acid profile crucial for bodily functions. The key to a balanced plant-based diet isn't focusing on a single food item but embracing variety. By including a mix of complete protein sources like soy products and pseudocereals, alongside high-protein vegetables and other legumes, individuals can easily meet all their essential amino acid requirements. Focusing on a variety of nutrient-dense, plant-based foods, rather than fixating on individual limitations, is the most effective approach to balanced nutrition.

For more detailed nutritional information on amino acids and vegetarian diets, consider consulting authoritative sources like the National Institutes of Health.

Frequently Asked Questions

Yes, it is entirely possible to get all nine essential amino acids from a plant-based diet. While most individual plant foods are 'incomplete' proteins, containing different amino acids, eating a variety of plant proteins throughout the day ensures you receive a full and balanced amino acid profile.

While most vegetables are not complete proteins on their own, some plant foods contain all nine essential amino acids and are often grouped with vegetables. These include soybeans (edamame, tofu), quinoa, amaranth, and buckwheat.

Among commonly consumed vegetables, green peas and edamame often rank highest in protein content. A cup of cooked green peas provides about 8 grams of protein, while a cup of cooked edamame contains nearly 18 grams.

No, spinach and broccoli are not considered complete proteins as they lack some essential amino acids. However, they are still excellent sources of protein and numerous other nutrients. The amino acids they provide can complement those found in other foods, like grains or legumes.

Vegans can easily get enough protein by eating a varied diet that includes a mix of legumes, whole grains, nuts, seeds, and protein-rich vegetables. Combining different plant foods, like beans with rice, helps to form a complete protein profile over the course of the day.

Complementary proteins are pairs of plant foods that, when eaten together, provide all nine essential amino acids. For example, beans and rice is a classic combination. Although once believed necessary in the same meal, it's now understood that eating a variety of these foods throughout the day is sufficient.

Cooking can affect the amino acid content and digestibility of some vegetables. Some studies show that processing, especially high-heat methods, can reduce certain amino acid levels, while others indicate that cooking improves overall digestibility. For optimal amino acid and nutrient intake, a mix of raw and cooked vegetables is recommended.