Is Soy a Complete Protein?

Soy foods offer a variety of nutritional benefits. They provide vitamins and minerals, including B vitamins, iron, zinc and antioxidants, along with fiber, heart-healthy omega-3 fats and high-quality protein. Learn what makes soy a complete protein and how it compares to other protein sources.

Complete Versus Incomplete Protein

Proteins are made up of amino acids, which also serve as a source of energy for the body. While the body can produce some amino acids, the nine essential amino acids — histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine — must come from food.

Foods that contain all nine essential amino acids, such as soy foods, are considered complete proteins, while those that contain only some are considered incomplete proteins.

Complete protein sources

Incomplete protein sources

  • Nuts
  • Legumes
  • Seeds
  • Vegetables
  • Whole grains

Soy is one of the few plant-based foods that provides all nine essential amino acids, making it an easy way to add complete protein to your diet. From everyday meals to plant-forward eating patterns, soy offers a simple and versatile way to meet your nutrition goals.
Learn More

Complete Plant Protein

Soy foods like tofu, edamame, tempeh and soy milk are complete proteins, making them a high-quality source of plant-based protein.

Pair with Other Plant Foods

Although many plant-based proteins are considered incomplete, they can still help meet your protein needs. Eating a variety of plant foods throughout the day helps provide the nutrients your body needs.

Easy to Add to Meals

Pour soy milk with breakfast, toss edamame into a salad or incorporate tofu or tempeh into your favorite recipes for an easy protein boost.

Soy Myths and Facts

About Us

Stay in Touch

Soy Connection is a collaboration of health, nutrition and food industry experts with U.S. soybean farmers to educate on the benefits of sustainably grown U.S. soybeans, including heart-healthy soybean oil and soy protein. Soy Connection is brought to you by U.S. Soy and the United Soybean Board (USB), a national checkoff funded by U.S. soybean farmers. © 2026 United Soybean Board.

    Soy Connection logo