There are a lot of misconceptions and myths when it comes to plant-based diets, and one that never seems to die down is “complementary protein” myth, where it’s said that vegetarians and vegans can end up protein deficient because plant foods don’t contain all the essential amino acids that humans need. That to be healthy we must either eat animal protein or combine certain plant foods with others in order to ensure that we get “complete proteins”.
The “incomplete protein” myth is actually one of the oldest myths relating to vegetarianism, veganism, and plant-based diets, which was disproved a very long time ago.
Where Does the “Complementary Protein” Myth Come From?
Jump back to 1971 and a book called Diet for a Small Planet, by Frances Moore Lappé, was the first major book to critique the impact of meat production. The groundbreaking book sold over 3 million copies and described the environmental impact of meat production as wasteful and a major contributor to global food scarcity. Lappé argued in favour of environmental vegetarianism as being what’s best for our bodies and the Earth, while informing the world that global hunger is not caused by a lack of food, but inefficient food policy.
While there’s absolutely nothing wrong with her argument given the extreme damage animal agriculture is having on the environment, she did make one error that she later openly retracted. Lappé realised there was a lot of waste in converting vegetable protein into animal protein, and she calculated that if people just ate the plant protein directly, many more people could be fed. As a sociologist trying to end world hunger, and not a nutritionist, physiologist, or medical doctor, Lappé stated that that plant foods are deficient in some of the essential amino acids so in order to be a healthy vegetarian, you needed to eat a combination of certain plant foods at the same time in order to get all of the essential amino acids in the right amounts. It was called the theory of “protein complementing”.
This is when and where the myth of plant-based diets being inherently difficult and inferior to animal protein began.
In the 1991 20th anniversary edition of her book, she retracted her statement. Lappé basically said that in trying to end one myth—the unsolvable inevitability of world hunger, she created a second one—the myth of the need for “protein complementing.” Humans don’t need every single of the nine essential amino acids in every bite of food in every meal we eat; we only need a sufficient amount of each amino acid every day.
In these later editions, she corrects her earlier mistake and clearly states that all plant foods typically consumed as sources of protein contain all the essential amino acids, and that humans are virtually certain of getting enough protein from plant sources if they consume sufficient calories.
The term “complete protein” refers to amino acids, the building blocks of protein. There are 20 different amino acids that can form a protein, and nine that the body can’t synthesise on its own. These are called essential amino acids—we need to eat them because we can’t make them ourselves. In 1952, William Rose and his team completed research that determined the human requirements for the nine essential amino acids that must come from our diet.
Today, if you calculate the amount of each essential amino acid provided by unprocessed plant foods and compare these values with those determined by William Rose, you will find that any single one, or combination, of these whole natural plant foods provides all of the essential amino acids. Furthermore, these whole natural plant foods provide not just the “minimum requirements” but provide amounts far greater than the “recommended requirements.”
Modern researchers know that it is virtually impossible to design a calorie-sufficient diet based on unprocessed whole plant foods that is deficient in any of the essential amino acids (the only possible exception could be a diet based solely on fruit). There has been a growing amount of scientific data that supports that a well-balanced, plant-based diet will provide adequate amounts of essential amino acids and prevent protein deficiency. Government bodies and health organisations around the globe recommend plant-based diets as a viable option for individuals of all ages.
The “incomplete protein” myth just won’t die despite evidence to the contrary. Commonly quoted by meat eaters and anti-vegan individuals or groups is the 2001 medical journal article on the hazards of high-protein diets where the Nutrition Committee of the American Heart Association wrote, “Although plant proteins form a large part of the human diet, most are deficient in one or more essential amino acids and are therefore regarded as incomplete proteins.”
This article is now referenced as some apparent irrefutable proof that plant-based diets are inferior and that those consuming such a diet will waste away or become inevitably ill. This is literally false information.
However, medical doctor and writer John McDougall wrote to the editor pointing out the mistake. But in a stunning example of avoiding science for convenience or perhaps a more sinister reason, instead of acknowledging their mistake, Barbara Howard, Ph.D., head of the Nutrition Committee, replied on the 25 June 2002 to Dr. McDougall’s letter and stated (without a single scientific reference) that the committee was right and “most (plant foods) are deficient in one or more essential amino acids.”
Without a single scientific reference, the so called Nutrition Committee refused to acknowledge their mistake out of pure laziness, ego, or because they were in favour of pushing this misconception into the medical and nutrition world.
Research Properly, Don’t Spread the Myth
Even a 2002 article in the Vegetarian Times made the same mistake. The author, Susan Belsinger, incorrectly stated, “Incomplete proteins, which contain some but not all of the EAAs [essential amino acids], can be found in beans, legumes, grains, nuts and green leafy vegetables…. But because these foods do not contain all of the EAAs, vegetarians have to be smart about what they eat, consuming a combination of foods from the different food groups. This is called food combining.”
Unfortunately, this example yet again perpetuated false information among the vegetarian community that had already been retracted and disproved.
Always Correct a Myth
It’s critical that the “incomplete protein” and “complementary protein” myth is corrected and expelled anytime it is referenced or quoted. Many people are afraid to follow a healthy plant-based diet because they stress and worry about “incomplete proteins” and becoming ill. A plant-based diet based on any single one or combination of these unprocessed starches (e.g. rice, corn, potatoes, beans), with the addition of vegetables and fruits, and some fortified foods such as plant milks, supplies all the protein, amino acids, essential fats, minerals, and vitamins necessary for excellent health.
To wrongly suggest that people need to eat animal protein for nutrients will encourage them to eat foods that are known to contribute to heart disease, diabetes, obesity, and many forms of cancer, to name just a few common problems.