Do Plants Have Protein?

A common misconception is that plants are poor protein sources, often due to the belief that some plants don’t contain “complete” proteins.

• A complete protein provides all nine essential amino acids.
• An incomplete protein lacks one or more of the nine essential amino acids.

Let’s begin by understanding these amino acids.

Protein, Amino Acids, and Your Body

Proteins are like Lego creations made from tiny building blocks called amino acids. Out of the twenty amino acids, nine are considered essential, meaning we must get them from food because our bodies can’t make them on their own. These amino acids can be arranged in so many different ways to build thousands of unique proteins. Each chain of amino acids twists, folds, and combines into different shapes to form a wide variety of proteins, each with its own important job.¹ It’s this amazing flexibility that allows your body to grow, repair, and function every day.

In fact, amino acids play many important roles in keeping the body healthy. They help your body build and repair muscles, support a strong immune system, and protect your heart, nerves, and muscles from damage.² Some amino acids also help your body make hormones and enzymes, balance fluids, support healthy bones, and even assist with movement and coordination.² Together, these tiny molecules do big jobs that affect nearly every system in the body.

Animal proteins have all the nine essential amino acids and are therefore considered complete proteins. While all plant foods contain some protein, most are considered incomplete—though there are a few exceptions.³

Plant-Based Sources of Complete Protein

Plant foods that have complete protein are:

• Amaranth
• Some edible mushrooms (e.g. button, oyster, and shiitake)
• Blue-green algae (also called Spirulinia)
• Buckwheat
• Chia seeds
• Hempseed
• Quinoa
• Soy (edamame, miso, soy milk, tempeh, tofu).^4,5,6,7,8

Even so, you don’t need to eat only plant foods with complete proteins to get all the amino acids your body needs to function properly. As long as you eat a mix of protein-containing plant foods such as grains, vegetables, legumes, nuts, seeds, and fruits throughout the day, your diet will likely provide all nine essential amino acids. This flexibility dispels the old myth of “protein combining” at each meal, which suggested that foods like rice and beans must be consumed together in the same meal.⁹ This concept, known as protein complementation, involves combining two incomplete plant protein sources to obtain all the essential amino acids. Examples of protein complementation include peanut butter on whole wheat bread, hummus with pita bread, corn chips with bean dip, and yogurt with nuts or seeds. What matters most, however, is total variety and adequate protein intake spread across the day.

Plant-Based Protein – Variety is Key!

You need to eat a variety of plant foods to get the amino acids your body needs from plant proteins. One of the best places to start is with legumes (beans, lentils, and peas), as well as nuts, seeds, and soy products.¹⁰ In fact, USDA MyPlate lists these foods among the protein group because they are excellent sources of plant protein, and provide antioxidants and key nutrients like fiber, potassium, iron and zinc.¹¹ To guide your choices, here are some food examples in these categories from MyPlate:¹²