Protein: Basics

by Jack Norris, RD

Contents

• Introduction
• Plant Protein and Amino Acids
• Protein Recommendations for Vegans

Introduction

Protein is important for maintaining muscle and bone mass, for keeping the immune system strong, and preventing fatigue.

People not familiar with vegan nutrition often assume it’s terribly hard to get enough protein on a vegan diet, and that’s if they think there’s any protein in plant foods at all. On the other hand, once “educated,” many vegans have the opposite view, considering protein either a myth or believing it would be impossible for anyone not to get enough protein on a vegan diet.

The truth lies somewhere in between.

Plant Protein and Amino Acids

Proteins are made out of chains of amino acids. Some amino acids can be made by the body—generally from other amino acids—but some cannot. The ones that cannot are known as essential or indispensable.

Because some amino acids are essential, the amino acid requirements are as important as protein needs. But because the essential amino acids are found in fairly consistent amounts in the average diet of Americans, the U.S. Recommended Dietary Allowance (RDA) for protein also covers amino acid needs.

A common belief is that most plant foods are completely devoid of at least one essential amino acid, but the truth is that all plant proteins have some of every essential amino acid. As a general rule, legumes are lower in the essential amino acid methionine while most other plants foods are lower in lysine. In general, though, only lysine is likely to be a concern for most vegans because almost all vegans naturally eat plenty of foods high in methionine.

In the early 1970s, Frances Moore Lappe wrote a book, Diet for a Small Planet, that popularized the idea of combining plant proteins at each meal in order to get a balance of essential amino acids in order to form a complete protein. In particular, mixing legumes and grains ensures that a vegan is obtaining both lysine and methionine at each meal. But we now know that vegans don’t need to worry about combining proteins at individual meals in order to create a complete protein because our livers store essential amino acids to be used as needed. The 2009 American Dietetic Association’s Position Paper on Vegetarian Diets stated:

Plant protein can meet requirements when a variety of plant foods is consumed and energy needs are met. Research indicates that an assortment of plant foods eaten over the course of a day can provide all essential amino acids and ensure adequate nitrogen retention and use in healthy adults, thus complementary proteins do not need to be consumed at the same meal.

Protein Recommendations for Vegans

To ensure adequate protein status, vegans should eat 3-4 servings per day of high-protein foods that also are good sources of the amino acid lysine. Below is a list of protein foods from which to choose (weights listed are for one serving of ready-to-eat food):

• Legumes – 1/2 cup cooked
  • Beans – garbanzo (chickpea), kidney, pinto, navy (125-150 grams)
  • Lentils (100 grams)
  • Peas – split (100 grams) or green (80 grams)
  • Soyfoods – edamame (80 grams), tofu (125 grams), tempeh (165 grams), soy milk (1 cup or 250 mL), soy meats (3 oz or 85 grams)
  • Peanuts – 1/4 cup (35-40 grams)
• Seitan – 3 oz (85 grams)
• Quinoa – 1 cup cooked (185 grams)
• Pistachios – 1/4 cup (30 grams)
• Pumpkin seeds – 1/4 cup roasted (35 grams)

It’s hard to design a vegan diet that meets lysine requirements for someone who doesn’t exercise daily without including legumes, seitan, quinoa, pistachios, or pumpkin seeds. People who exercise have higher caloric needs, making it easier to meet lysine needs through other foods.

Athletes will require somewhat more servings of protein than listed above, but this will be based on their individual sport and training. See Sports Nutrition for more information.

There’s evidence that as people age, they need a higher percentage of their calories to be protein; people over 60 should focus on making the above high-protein foods a large part of their meals.

Vegans who don’t eat enough calories to maintain their weight should make an effort to include a higher percentage of high protein foods.

Last updated March 2023