Which nuts contain complete protein? Only one does

December 31, 2025 •

4 min read

Many people are surprised to learn that while most nuts are excellent sources of protein, they are considered 'incomplete' because they lack or are low in one or more essential amino acids. A balanced vegetarian or vegan diet requires carefully combining plant-based protein sources to ensure all nine essential amino acids are consumed. Pistachios, however, stand out as the rare exception among commonly consumed nuts, containing all nine essential amino acids in adequate amounts to be considered a complete protein source for people over five years old.

Quick Summary

This article explains why most nuts are incomplete proteins and highlights how pistachios are the notable exception. It details what constitutes a complete protein, how to combine incomplete protein sources, and the significant health benefits of pistachios and other nuts. The guide also clarifies the distinction between nuts and legumes like peanuts.

Key Points

Pistachios are a Complete Protein: Unlike most nuts, recent studies have confirmed that pistachios contain all nine essential amino acids, making them a complete protein source for those over five years old.
Most Nuts Are Incomplete: The majority of nuts, while protein-rich, are considered incomplete proteins because they are low or lacking in one or more essential amino acids, such as lysine.
Complementary Protein Combining: Those on plant-based diets can still obtain complete protein by pairing different incomplete protein sources, such as nuts with grains or legumes, over the course of a day.
Peanuts are Legumes, Not Nuts: Peanuts are technically legumes but are nutritionally similar to tree nuts and are also an incomplete protein, most often low in methionine.
Nuts Offer Broader Nutritional Benefits: All nuts, regardless of their complete protein status, are excellent sources of healthy fats, fiber, vitamins, minerals, and antioxidants, contributing to overall health.
Plant-Based Complete Proteins Exist: Beyond pistachios, other plant foods like quinoa, soy, and hemp seeds are also complete protein sources that can be incorporated into a balanced diet.
Variety is Key: The most effective nutritional strategy is to consume a wide variety of protein sources to ensure all essential amino acids are consistently met.

Understanding Complete vs. Incomplete Proteins

Proteins are fundamental to human health, acting as the building blocks for tissues, hormones, and enzymes. They are composed of smaller units called amino acids. Of the 20 amino acids, nine are considered 'essential' because the human body cannot produce them and must obtain them from food.

A complete protein is a food source that contains all nine of these essential amino acids in sufficient amounts. Animal-based products like meat, eggs, and dairy are classic examples. Incomplete proteins, on the other hand, lack or are low in one or more of these essential amino acids. Most plant-based protein sources, including the majority of nuts, fall into this category.

The Unique Case of Pistachios

Scientific research, particularly studies involving U.S.-grown pistachios, has confirmed that these green nuts are indeed a complete protein. This was a significant finding, as it solidified their status alongside other plant-based complete proteins like soy and quinoa. A single one-ounce serving of pistachios provides approximately 6 grams of complete protein, along with an impressive nutritional profile that includes healthy fats, fiber, antioxidants, and various vitamins and minerals. The protein quality of roasted pistachios has even been evaluated with a Protein Digestibility-Corrected Amino Acid Score (PDCAAS) of 81%.

Combining Incomplete Proteins for a Complete Amino Acid Profile

For those relying on a vegetarian or vegan diet, getting all essential amino acids doesn't depend on a single food. The concept of complementary proteins involves combining different plant foods over the course of a day to ensure all essential amino acids are consumed. Your body can store amino acids, so they don't all need to be consumed in the same meal.

Common complementary pairings include:

Nuts with whole grains: Peanut butter on whole-wheat bread or almonds in your oatmeal.
Legumes with whole grains: The classic combination of rice and beans or hummus with pita bread.
Nuts and seeds with legumes: A mixed salad with chickpeas and sunflower seeds or a lentil soup with a walnut topping.
Nuts with seeds: A trail mix combining different nuts like almonds and walnuts with seeds such as hemp and pumpkin seeds to create a more comprehensive protein source.

Comparing Nuts and Other Plant Proteins

While pistachios hold the title for complete protein among nuts, it's important to remember that all nuts offer significant nutritional value. Other sources like soy, quinoa, and hemp seeds are also complete proteins and are crucial for diversifying a plant-based diet. Legumes like beans and lentils are excellent protein sources that can complement nuts.


Food Type	Example	Protein per 100g (Approx.)	Complete Protein?	Complementary Pairing
Nuts	Pistachios	20 g	Yes	N/A (Complete)
Nuts	Almonds	21 g	No (Low in Lysine)	Quinoa or Lentils
Nuts	Walnuts	15 g	No (Low in Lysine)	Beans or Seeds
Seeds	Hemp Seeds	~31 g	Yes	N/A (Complete)
Grains	Quinoa	~14 g	Yes	N/A (Complete)
Legumes	Peanuts*	26 g	No (Low in Methionine)	Rice or Whole Grains

*Note: Peanuts are botanically legumes but are functionally and nutritionally similar to tree nuts.

The Broader Health Benefits of Nuts

Beyond their protein content, nuts are packed with heart-healthy monounsaturated and polyunsaturated fats, fiber, vitamins, and minerals. Regularly consuming nuts has been associated with numerous health benefits, including a reduced risk of heart disease, improved cholesterol levels, better blood sugar control, and even support for healthy gut bacteria. The fiber in nuts also contributes to a feeling of fullness, which can aid in weight management.

It is important to remember that all nuts contribute valuable nutrition, not just the single one that is technically a complete protein. A varied intake of different nuts, seeds, and legumes is the best strategy for a well-rounded diet, especially for those on plant-based regimens. The key is to embrace variety and understand how different foods work together to provide your body with everything it needs.

Conclusion: Variety is the True Key to Complete Nutrition

While the discovery that pistachios are one of the few plant-based complete proteins is an exciting development, it does not diminish the value of other nuts. Every type of nut offers a unique combination of beneficial nutrients. For a balanced diet, especially if following a plant-based regimen, it's about combining different protein sources throughout the day, not relying solely on a single 'complete' source. So, whether you're snacking on pistachios, topping a salad with walnuts, or enjoying a peanut butter sandwich, you can feel confident you're making a healthy choice. The overall takeaway is that variety is the most effective way to ensure you are consuming a complete protein profile through your diet. Learn more about plant-based diets and protein sources at the National Institutes of Health(https://pmc.ncbi.nlm.nih.gov/articles/PMC7434868/).

Frequently Asked Questions

A complete protein is a food source that contains all nine of the essential amino acids that the human body cannot produce on its own.

Pistachios are the only commonly consumed nuts to be classified as a complete protein. They contain all nine essential amino acids in adequate amounts.

Vegans and vegetarians can combine incomplete protein sources over the course of the day. For example, pairing nuts with whole grains, legumes, or seeds ensures all essential amino acids are consumed.

Peanuts are not complete proteins. They are technically legumes and, like most nuts, are low in specific essential amino acids, such as methionine.

Combining complementary proteins means eating foods that fill in each other's nutritional gaps. For instance, grains that may be low in one amino acid can be combined with nuts or legumes that are rich in it to create a complete amino acid profile.

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

No, you do not need to consume complete protein in every meal. The body can draw from a stored 'pool' of amino acids, so ensuring variety throughout the day is the most important factor.