What Is the Richest Source of Vegetable Protein?

November 12, 2025 •

3 min read

Spirulina, a blue-green algae, can contain up to 70% protein by dry weight, making it a surprising contender for the title of the richest source of vegetable protein. This microscopic organism packs a significant nutritional punch, rivaling many animal sources in its protein concentration.

Quick Summary

This article explores the highest-protein plant-based foods, crowning spirulina as the most concentrated source. It details other protein powerhouses like hemp seeds, legumes, and soy products, offering a comprehensive guide to meeting protein needs on a plant-based diet.

Key Points

Spirulina is the most protein-dense vegetable source: This blue-green algae can contain up to 70% protein by dry weight and is a complete protein.
Hemp seeds are a highly concentrated source: Hulled hemp seeds offer 30-35 grams of complete protein per 100 grams, making them a top contender.
Soy products provide complete protein: Tofu, tempeh, and edamame are excellent, complete protein sources derived from soybeans.
Legumes are reliable staples: Lentils and chickpeas are versatile and protein-rich, though they are best complemented with other plant sources for a full amino acid profile.
Dietary variety ensures complete nutrition: Combining different plant proteins throughout the day is the best way to get all essential amino acids, even if individual sources are 'incomplete'.
Nutritional yeast adds flavor and protein: This popular vegan condiment is a complete protein and can be sprinkled on various dishes for a nutritional boost.

The Unexpected Winner: Spirulina

When considering the richest source of vegetable protein, most people might think of soybeans or nuts. However, the true champion, based on protein concentration by dry weight, is spirulina. This blue-green alga, often sold as a powder or supplement, is a powerhouse of nutrients. With a protein content that can range from 55% to 70%, it surpasses most conventional plant-based options. It is also a complete protein, meaning it contains all nine essential amino acids that the human body cannot produce on its own.

Why Spirulina is a Protein Powerhouse

The high digestibility of spirulina's protein is another key advantage. Unlike many plants with cell walls made of indigestible cellulose, spirulina's cell walls are composed mainly of proteins, carbohydrates, and lipids, which are easily broken down by the human digestive system. This makes its protein highly bioavailable. While it may not be a common food in Western diets, a small amount of spirulina powder added to smoothies, juices, or energy balls can significantly increase the protein content of a meal.

Top Contenders in the Plant-Based Protein World

While spirulina takes the crown for density, other plant-based foods offer excellent protein content and are more accessible for daily meals.

Seeds: Hemp seeds (or hemp hearts) are an outstanding source, providing around 30-35 grams of protein per 100 grams. Like spirulina, they are also a complete protein source. Other high-protein seeds include pumpkin seeds (up to 30g per 100g) and chia seeds (around 16.5g per 100g). These are simple to add to salads, oatmeal, or baked goods for a quick protein boost.
Legumes: This food family is a staple for plant-based diets. Dry soybeans are extremely high in protein, often containing over 35% protein by dry weight. When boiled, they still provide an impressive ~17-18 grams of protein per 100 grams. Products derived from soy, like tempeh (fermented soybeans), contain around 20.7 grams of protein per 100 grams, while firm tofu offers about 17.3 grams. Lentils are another top-tier legume, with dried varieties providing 25-26 grams of protein per 100 grams. Cooked lentils provide slightly less due to water content but remain a rich source. Peanuts, technically legumes, also boast high protein levels.
Grains and Pseudocereals: Quinoa is widely recognized as a complete protein, offering all nine essential amino acids. A cooked cup provides around 8 grams of protein. Other high-protein grains and pseudocereals include amaranth, buckwheat, and teff.
Nutritional Yeast: Often a flavor enhancer for vegans, nutritional yeast is a deactivated yeast that is a complete protein source. It provides around 8-9 grams of protein per 2 tablespoons and can be used to add a cheesy, savory flavor to dishes.

Comparison of Richest Vegetable Protein Sources

To put these options into perspective, the table below compares the protein content of several of the richest vegetable protein sources per 100g.


Food (per 100g)	Protein Content (approx.)	Source Type	Complete Protein?
Spirulina (dry powder)	55-70g	Microalgae	Yes
Hemp Seeds (hulled)	30-35g	Seed	Yes
Soybeans (dry)	36-56g	Legume	Yes
Tempeh	20.7g	Legume Product	Yes
Lentils (dried)	25-26g	Legume	Incomplete*
Tofu (firm)	17.3g	Legume Product	Yes

*Lentils are high in lysine but low in methionine, so should be combined with a grain like rice for a complete profile.

The Importance of Complete Proteins

While some plant sources like soy, quinoa, and hemp are complete proteins, many are not. This is not a cause for concern, as consuming a variety of plant-based protein sources throughout the day, known as complementary proteins, is sufficient to provide all essential amino acids. For example, combining legumes (like beans) with whole grains (like rice) over the course of a day can fulfill the body's needs. This makes a varied, whole-food plant-based diet a simple and effective way to ensure adequate protein intake without meticulous planning.

Conclusion

While spirulina is technically the richest source of vegetable protein by concentration, a balanced diet rich in a variety of other high-protein plant foods is more practical for most people. Combining staples like legumes, soy products, nuts, and seeds ensures a broad intake of essential amino acids and other vital nutrients. Focusing on dietary variety rather than a single source is the most effective strategy for thriving on a plant-based diet. Exploring options like hemp seeds in morning smoothies, lentils in stews, or tofu in a stir-fry offers delicious and diverse ways to boost daily protein intake. You can read more about plant-based proteins on sites like Healthline to further expand your knowledge of nutrition.

Frequently Asked Questions

While spirulina is the most protein-dense by weight, other vegetables offer an excellent protein-to-calorie ratio. Edamame and spinach are particularly high in protein relative to their low-calorie count, making them a great choice for those monitoring caloric intake.

Yes, it is entirely possible to get all essential amino acids from vegetable protein. By consuming a variety of plant foods throughout the day, such as legumes combined with grains, you can easily meet your needs for a complete protein profile. Additionally, some plant foods like soy, quinoa, and hemp seeds are complete proteins on their own.

Yes, hemp seeds are one of the few plant-based foods that are considered a complete protein, meaning they contain all nine essential amino acids. They are also rich in healthy fats and other nutrients.

Spirulina, especially in its dry powder form, is extremely protein-dense, with studies citing a protein content of 55-70% by dry weight. This makes it one of the most concentrated protein sources available, plant or animal.

Both tofu and tempeh are excellent sources of protein derived from soybeans. Tempeh often has a higher protein content per 100g than firm tofu, along with more fiber due to being made from the whole fermented soybean. However, both are fantastic, complete protein options.

Vegans can combine complementary protein sources throughout the day to ensure they consume all essential amino acids. Classic pairings include rice and beans, pita and hummus, or a peanut butter sandwich on whole-grain bread. Since the body stores amino acids, you don't need to pair them in the same meal.

For muscle building, consistency and total protein intake are more important than any single source. High-quality, complete plant proteins like spirulina, hemp seeds, and soy products (tofu, tempeh) are all excellent choices. Combining them with consistent strength training provides the necessary amino acids for muscle repair and growth.