How Vegetarian Diets Include Protein: Plant vs. Animal Proteins

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  • 0:03 Plant & Animal Proteins
  • 1:23 Protein Complementation
  • 3:26 Lacto-Ovo Vegetarian Diet
  • 4:07 Lesson Summary
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Most plant-based foods only offer incomplete proteins, meaning they do not contain all of the needed amino acids. Animal products, on the other hand, are a good source of complete proteins, but vegetarian diets limit these foods. Learn how vegetarians can meet their protein needs in this lesson.

Plant and Animal Proteins

If you're a fan of cartoons, you might recall a certain sailor man who was known for his big muscles as well as his love for spinach. Now, big muscles and leafy green vegetables, like spinach, might not be two things you instinctively put together, yet there is protein in spinach, and protein is a necessary nutrient for the building of structures in the body, including muscle.

That's the good news. The not so good news for vegetable lovers is that the protein obtained from spinach and most plant-based foods are generally incomplete proteins, which means they lack one or more of the essential amino acids needed by the body. In comparison, when animal products are consumed they generally provide the body with complete proteins, meaning these foods contain all of the essential amino acids needed by the body.

So, you might be wondering how you would get all of the needed amino acids into your body if you prefer to follow a vegan diet, which is a diet that contains only plant-based food, or a vegetarian diet, which is a diet that contains mostly plant-based foods with only limited animal products. Well, it is possible, but it requires some planning. In this lesson, we will take a look at how vegetarian or vegan diets can be designed in a way that meets a person's nutritional needs.

Protein Complementation

Plant-based foods include vegetables, fruits, grains, legumes, nuts and seeds. These foods, with only a few exceptions, such as quinoa and soybeans, contain incomplete proteins. A well-planned vegetarian or vegan diet is one that mixes different plant-based proteins sources together. By combining various incomplete proteins, a vegetarian or vegan can obtain all of the amino acids needed for good health.

For example, legumes, which are a class of vegetables that includes beans, peas, peanuts and lentils are a poor source of the amino acid methionine, but high in lysine. By contrast, grains, such as barley, corn, rice and oats, are a good source of methionine, but low in lysine. Therefore, a vegetarian or vegan should combine legumes with grains for a more complete mix of essential amino acids.

This strategy of combining incomplete proteins to form a complete protein is known as protein complementation. Many traditional diets naturally use the protein complementation strategy. For example, popular dishes in India often combine lentils with rice or chickpeas and popular dishes in Mexico often combine beans and rice.

Of course, there are also some popular American foods that work together, such as a peanut butter sandwich. This quick meal combines a grain from the bread with a legume supplied by the peanuts in the peanut butter. Protein complementation is needed to ensure that vegetarians and vegans are getting all the essential amino acids, yet these foods do not need to be consumed in the same meal; eating a variety of plant foods throughout the day works as well.

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