What is the highest quality plant-based protein?

November 13, 2025 •

4 min read

According to the Food and Agriculture Organization of the United Nations, a truly high-quality or "complete" protein must contain adequate levels of all nine indispensable amino acids. So, what is the highest quality plant-based protein, and how can plant-based eaters optimize their protein intake to meet nutritional needs?

Quick Summary

This article explores the highest quality plant-based protein sources, detailing the metrics for protein quality, such as complete amino acid profiles and bioavailability. It compares popular options like soy, pea, and hemp, providing practical guidance for optimal protein consumption in a plant-based diet.

Key Points

Complete vs. Incomplete: A complete protein contains all nine essential amino acids. While most plant proteins are incomplete on their own, a varied diet can easily provide a complete amino acid profile.
Soy is a Top Contender: Soy is one of the few plant proteins that is naturally complete and highly digestible, with soy protein isolate achieving a perfect PDCAAS score of 1.0.
Combine for Completeness: Combining different plant protein sources, like rice and peas, can create a complete amino acid profile, particularly in supplements and protein powders.
Bioavailability Varies: Animal protein is generally more bioavailable, but the difference with plant protein is insignificant for most people meeting their daily requirements. Cooking and soaking can improve plant protein absorption.
Diversity is Key: The most effective strategy for high-quality plant-based protein is consuming a variety of sources, including legumes, grains, nuts, and seeds, throughout the day.
Beyond Amino Acids: The quality of plant protein extends beyond its amino acid profile; whole plant foods offer fiber, antioxidants, and other beneficial compounds.

Understanding Protein Quality

To determine the highest quality plant-based protein, it's essential to understand the criteria used to measure protein quality. The gold standard for many years has been the Protein Digestibility Corrected Amino Acid Score (PDCAAS), which assesses how digestible a protein is and how complete its amino acid profile is relative to human needs. A score of 1.0 is considered the highest possible, though a newer metric, the Digestible Indispensable Amino Acid Score (DIAAS), is now also used and is considered more accurate as it accounts for the digestibility of individual amino acids.

Complete vs. Incomplete Proteins

Proteins are made up of 20 amino acids, and our bodies can produce 11 of these. The remaining nine are 'essential' and must be obtained from our diet. A 'complete' protein contains all nine essential amino acids in sufficient quantities. While most animal proteins are complete, many plant proteins are 'incomplete' as they are low in one or more essential amino acids. However, this does not mean they are inferior; by combining a variety of plant-based foods, you can easily create a complete protein profile over the course of a day. The concept of needing to combine complementary proteins in the same meal has been largely debunked.

Bioavailability

Bioavailability refers to how easily the body can break down, absorb, and utilize the amino acids from a food source. Animal proteins are generally more bioavailable than plant proteins, but the difference is minimal for those meeting their daily protein requirements. Some plant proteins contain 'antinutrients' like phytates and tannins, which can slightly interfere with absorption, but these are often reduced by cooking and offer health benefits of their own.

The Top Contenders for Highest Quality Plant-Based Protein

While there is no single 'highest' quality, certain plant-based proteins consistently rank high due to their complete amino acid profile, digestibility, and overall nutritional benefits.

Soy Protein

Soy protein, found in products like tofu, tempeh, and edamame, is a long-standing champion of plant-based protein. It is one of the few plant sources that provides a complete amino acid profile naturally. Soy protein isolate often scores a perfect 1.0 on the PDCAAS, making its quality comparable to animal proteins like whey and casein. It is also highly digestible and rich in other nutrients like iron, calcium, and fiber, especially in whole food forms. Some studies also highlight soy's potential benefits for heart health.

Quinoa and Amaranth

These ancient 'pseudocereals' are other notable complete protein sources. A cooked cup of quinoa offers around 8 grams of protein and is packed with minerals like magnesium and iron. Amaranth, with 9 grams of protein per cooked cup, also boasts an impressive nutrient profile. Their versatility allows them to be used in everything from breakfast porridge to dinner salads.

Hemp Seeds

Hemp seeds are another complete protein, containing about 10 grams of protein in a 3-tablespoon serving. Beyond their protein content, they are a fantastic source of heart-healthy omega-3 and omega-6 fatty acids, magnesium, and iron. They can be easily sprinkled on yogurt, salads, or blended into smoothies for a nutty flavor and nutritional boost.

Blended Plant Proteins and Complementation

As discussed, combining different plant protein sources is a simple and effective strategy to ensure a complete amino acid intake. This is particularly relevant for plant-based protein powders, where blending complementary sources like pea and rice can create a complete protein product.

A Comparison of Plant Proteins


Protein Source	Protein Quality Score (PDCAAS)*	Limiting Amino Acid(s)	Notable Benefits
Soy Protein Isolate	1.0	None	Complete amino acid profile, high digestibility, heart health support
Pea Protein Concentrate	0.89	Methionine	High in branched-chain amino acids (BCAAs), hypoallergenic, highly digestible
Hemp Seeds (Whole)	0.49–0.53	Lysine, Threonine, Tryptophan	Rich in omega fatty acids, fiber, minerals
Quinoa	0.77-0.89	None (Complete)	High in magnesium, iron, and fiber
Rice Protein	0.50	Lysine	Hypoallergenic, easy to digest, pairs well with pea protein

*The PDCAAS is a widely cited metric, though DIAAS may offer more precise data. Scores for whole foods can vary.

Optimizing Your Plant-Based Protein Intake

Consuming a variety of whole plant foods throughout the day is the most reliable method for meeting all your amino acid requirements. This variety ensures that the amino acids that might be low in one food are compensated for by another. For example, pairing lysine-rich beans with methionine-rich rice is a classic complementary combination.

For athletes: Consider incorporating high-quality, complete sources like soy or a blended protein powder to support muscle recovery and growth.
For general health: Focus on dietary diversity, including a mix of legumes, whole grains, nuts, and seeds. Foods like edamame, lentils, and chickpeas are excellent whole-food options.
Utilize supplementation: If your intake from whole foods is inconsistent, a protein powder blend of pea and rice or a soy isolate can ensure you get a balanced amino acid profile.

Conclusion: The True Winner is a Varied Diet

Ultimately, there is no single best answer to the question, 'What is the highest quality plant-based protein?' While soy protein isolate and whole foods like quinoa are technically complete and highly digestible, the superior strategy lies in dietary diversity. By incorporating a variety of legumes, grains, nuts, and seeds, you can easily meet all your essential amino acid needs. Focusing on a well-rounded and varied diet ensures not only adequate protein but also a wealth of other nutrients, fiber, and phytochemicals that contribute to overall health and wellness. Rather than seeking a single miracle source, embrace the power of diverse plant foods to build a robust and complete protein profile over the course of your day.

Frequently Asked Questions

No, it is not necessary to combine complementary protein sources at every meal. Your body maintains a pool of amino acids throughout the day, and as long as you eat a varied diet, it can draw from this pool to meet all its needs.

Yes, moderate consumption of soy protein is generally safe and associated with numerous health benefits, including supporting heart health and bone density. Concerns about hormonal effects are largely unsubstantiated by research.

While pea protein is highly digestible and rich in BCAAs, it is lower in the essential amino acid methionine compared to soy, which is a complete protein. For this reason, pea protein is often blended with rice protein to balance the amino acid profile.

Some plant sources, like soy, quinoa, and hemp seeds, are considered complete proteins and can be relied upon alone. However, focusing on a diverse intake of plant-based foods is the best way to ensure you get all essential amino acids and a broader spectrum of nutrients.

Yes, studies have shown that plant protein, particularly blends like pea and rice, can be just as effective as animal protein (like whey) for promoting muscle growth and recovery, especially when overall dietary needs are met.

Cooking can actually improve the quality of some plant proteins. It can reduce the effect of 'antinutrients' that may hinder protein absorption and make the protein more digestible overall.

The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is a method for evaluating protein quality based on amino acid needs and digestibility. Plant proteins typically have lower scores than animal proteins, but high-quality sources like soy protein isolate can score a perfect 1.0.