by Jack Norris, RD • Last updated January 2016
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 even think there’s any protein in plant foods at all—it’s not clear how they think vegans survive.
On the other hand, once “educated,” many vegans have the opposite view—considering protein either a myth or that it would be impossible for anyone not to get enough on a vegan diet.
The truth lies somewhere in the middle.
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 is able to account for amino acid needs.
The percentages of essential amino acids in both animal and soy products closely mimic those found in human proteins, and they are, therefore, considered complete or high-quality protein. Non-soy plant proteins have a lower percentage of at least one amino acid, although all legumes are almost as “complete” as soy.
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 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 an effort to make sure vegetarians were getting enough of all the amino acids, in the early 1970s in her book Diet for a Small Planet, Frances Moore Lappe popularized the idea of combining plant proteins at each meal in order to get a “complete” protein. The idea was that mixing beans and grains would allow you to ensure that you’re getting both methionine and lysine at each meal.
Since the 1980s, it’s been well known that our livers store the various essential amino acids. For example, the 2009 American Dietetic Association’s Position Paper on Vegetarian Diets says:
“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.”
In other words, just get enough lysine in general and you don’t need to worry about combining proteins.
Protein Recommendations for Vegans
To ensure adequate protein status, vegans should eat 3–4 servings per day of the following foods which are both high in protein and the amino acid lysine:
- Legumes—1/2 cup cooked
- Beans—garbanzos, kidney, pinto, navy
- Peas—split or green
- Soyfoods—edamame, tofu, tempeh, soy milk (1 cup), soy meats (3 oz)
- Peanuts—1/4 cup
- Seitan—3 oz (85 g)
- Quinoa—1 cup cooked
- Amaranth (grain) – 1 cup cooked
- Pistachios—1/4 cup
- Pumpkin seeds—1/4 cup roasted
It’s hard to design a vegan diet that meets lysine requirements for a person who doesn’t exercise daily without including legumes, seitan, quinoa, pistachios, or pumpkin seeds and therefore without having too many calories. It’s easier to design a vegan diet for regular exercisers whose calorie requirements are higher—the low lysine foods will add up to provide enough.
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—thus 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.