Can you combine plant proteins to make a complete protein?

November 14, 2025 •

3 min read

Decades ago, a popular book created the myth that vegans must combine specific plant foods at every meal to form a complete protein. The truth is far simpler: you can combine plant proteins to make a complete protein over the course of a day with a varied diet.

Quick Summary

A varied diet of plant foods provides all nine essential amino acids needed to form a complete protein. The old rule about combining proteins in a single meal is outdated, according to modern nutritional science.

Key Points

Amino Acid Pool: The body stores and recycles amino acids, so combining proteins over the course of a day is sufficient, not at every single meal.
Diverse Diet is Key: Eating a variety of plant foods like legumes, grains, nuts, and seeds ensures you get all essential amino acids.
Some Plants are Complete: Certain plant foods, such as soy, quinoa, hemp seeds, and buckwheat, are naturally complete proteins on their own.
Combine Incomplete Proteins: Pairings like rice and beans, or hummus and pita, create a complete protein by complementing each other's amino acid profiles.
Outdated Myth: The idea that you must combine proteins at the same meal was popularized in the 1970s but has since been retracted by its original proponent and disproven.
Nutrient-Dense Option: Plant protein sources often come with added benefits like fiber and antioxidants, unlike many animal proteins.

Understanding the Building Blocks: Amino Acids

Protein is a crucial macronutrient made up of smaller units called amino acids. Of the 20 total amino acids, your body can produce 11 on its own, which are known as non-essential amino acids. The remaining nine are called essential amino acids because they must be obtained through food.

Complete Protein: A food that contains all nine essential amino acids in sufficient amounts. Animal products like meat, eggs, and dairy are traditionally considered complete proteins.
Incomplete Protein: A food that is low in or missing one or more of the essential amino acids. Most plant foods are considered incomplete, but this doesn't mean they are nutritionally inferior. It just means they might be limiting in certain amino acids, which can be balanced by other foods in a varied diet.

The Outdated Myth of Protein Combining

For many years, the idea that plant-based eaters needed to carefully combine specific plant foods at every meal to create a "complete protein" was prevalent. However, this concept has been debunked by the nutrition community. The human body effectively utilizes amino acids from the foods you eat throughout the day due to an "amino acid pool". Consuming a variety of protein sources over the course of a day is sufficient to provide all essential amino acids.

Plant-Based Complete Protein Sources

While many plant proteins are considered incomplete, some are complete on their own. Soy products like tofu and tempeh, quinoa, buckwheat, hemp seeds, chia seeds, and pistachios are examples of complete plant proteins. Spirulina is also a complete protein.

Classic Complementary Protein Pairings

Pairing foods where one provides the limiting amino acid of the other can create balanced meals. A common example is combining grains and legumes, as grains are often low in lysine and legumes are low in methionine, offering a full amino acid profile together. Examples include beans and rice, or hummus and whole-wheat pita. Combining legumes with nuts or seeds can also be complementary.

Plant vs. Animal Protein: A Comparison

A comparison of plant and animal proteins shows differences in amino acid profiles, nutrient density, and environmental impact. Animal protein is typically complete, while plant protein varies, though many plant sources offer fiber, vitamins, and minerals. Plant-based diets generally have a lower ecological footprint and are associated with a reduced risk of chronic diseases compared to excessive animal protein intake.

Planning a Complete Plant-Based Diet

Ensuring adequate protein on a plant-based diet involves variety and sufficient calories. A diverse diet of different plant foods naturally provides a range of amino acids. Incorporating complete proteins like soy and quinoa simplifies meal planning. Protein deficiency is uncommon with a varied, calorie-sufficient diet.

Conclusion

The idea of combining specific plant proteins at every meal for a complete protein is a myth. A diverse diet of plant foods throughout the day provides the body with all essential amino acids needed. This approach also offers beneficial fiber and micronutrients. For further reading on this topic, consider {Link: Forks Over Knives https://www.forksoverknives.com/wellness/the-myth-of-complementary-protein/}.

Frequently Asked Questions

No, you do not need to combine plant proteins at every meal. Your body maintains a pool of amino acids from the foods you eat, and as long as you consume a variety of plant foods throughout the day, your amino acid needs will be met.

A complete protein is a food source that contains all nine essential amino acids in adequate amounts. Essential amino acids are those your body cannot produce on its own.

Several plant foods are considered complete proteins, including soy products (tofu, tempeh, edamame), quinoa, buckwheat, hemp seeds, chia seeds, and spirulina.

A classic example is rice and beans. Grains like rice are low in the amino acid lysine, while beans are high in lysine but low in methionine. Eaten together, they form a complete protein.

The myth was popularized in the 1970s by the book Diet for a Small Planet. The author later clarified that combining proteins at every meal is not necessary, as the body is more efficient than that.

With adequate intake, plant protein can be just as effective as animal protein for building muscle, especially when combined with resistance training. The key is ensuring sufficient calories and a varied protein intake.

No. While many plant proteins are low in one or more essential amino acids, making them technically 'incomplete,' a number of plants like soy and quinoa are complete proteins. The key is dietary variety.

Focus on eating a wide variety of protein-rich plant foods like legumes, whole grains, nuts, and seeds throughout the day. Including complete plant proteins like soy and quinoa can also simplify your meal planning.

While not necessary for amino acid needs, combining complementary proteins in a single dish can create a delicious and nutritionally balanced meal. It is also a practice found in many traditional cuisines.