Vegetable proteins are “complete” as animal proteins : myth debunked

We live in this myth because of a preconception that we have been carrying since 1970, the “combining-protein theory”.


“If you only eat a plate with black beans, you don’t get the full protein. You have to add another type of bean to get the same type of protein that you would get from meat.”

This sentence referred to a diet of the moment called “combination of proteins” that became popular in the seventies. It was based on the premise that vegetarian and vegan diets provided insufficient content of essential amino acids, making it necessary to combine vegetable proteins to obtain the same “complete” protein that would be obtained from an animal. The combination of proteins has been discredited by the medical community, but there are still people who follow this practice, and more people who still believe that vegetable-based protein is incomplete.

What is a complete protein, anyway?

To be clear, a “complete protein” is a protein that contains all nine essential amino acids that our body needs to function: tryptophan.treonina, isoleucine, leucine, lysine, methionine + cystine, phenylalinine + tyrosine, valine and histidine. These amino acids are “essential”, but our bodies cannot get them, so they must be derived from the foods we eat. For the sake of completeness I underline that I have read that through the process of transamination even those and only 2 are really essential, but we remain on the canons 9

Although many vegans and vegetarians are concerned about getting enough protein, the concern about “full protein” has more to do with the quality of our protein than with the quantity.

So why have we been led to believe that animal proteins are more complete than vegetable proteins?

Misleading studies have triggered the popularity of a practice called ‘protein combination’ in the 1970s.

In 1909, the biochemist Karl Heinrich Ritthausen formulated the theory that vegetarian and vegan diets provide insufficient amounts of essential amino acids, making it necessary to combine vegetable proteins to obtain the same “complete” protein that would be obtained from an animal. Another 1914 study on Yale also suggested that vegetable-based protein was incomplete, but this research was conducted in newborn rodents.

Protein-combining theory gained popularity in 1954 with the publication of Adelle Davis’ book Let’s Eat Right to Keep Fit. The idea came even further forward in 1971, when Frances Lappé published the best-selling book, Diet for a Small Planet, which took up the same idea.  Vogue and the American Journal of Nursing also of the combination of proteins in 1975. At that point, America was on board.

But in 1981, Lappé changed his position on the combination of proteins in a revised edition of his book, in which he took a step back on all theory and apologized for strengthening a myth.

The greatest downward push to the theory came in 2002, when Dr. John McDougall issued a correction to the American Heart Association for a 2001 publication that questioned the completeness of plant proteins.


“Previous research on plant proteins was misleading, impossible to design a amino diet

John McDougall

deficient acid based on the amount of unprocessed starches and vegetables sufficient to meet the caloric needs of humans, In addition, it is not necessary to mix foods to obtain a complementary amino acid composition. The reason why it is important to correct this misinformation is that many people are afraid to follow healthy vegetarian diets and as well, worry about ‘incomplete proteins’ from plant sources. A vegetarian diet based on one or more of these unprocessed starches (e.g. rice, corn, potatoes, beans), with the addition of fruits and vegetables, provides all the proteins, amino acids, essential fats, minerals and vitamins (except vitamin B12) needed for excellent health. Incorrectly suggesting that people need to eat animal protein for their nutrients will encourage them to add foods that are known to contribute to heart disease, diabetes, obesity and many forms of cancer, to some common problems.



So if all the proteins are complete, are they the same?
10 grams of lentil proteins have the same effect on the body as 10 grams of steak proteins?

Dr. Greger went on to say: “Although both are considered complete, there are differences. For example, lentil does not increase IGF-1 levels as much as beef protein, which is one of the reasons why beef is likely to be a human carcinogen and the consumption of legumes on the other hand is associated with a lower risk of cancer. Lentils would probably be even better for our kidneys as well as for longevity.”

How much protein do we really need, anyway?

“Whether vegans, vegetarians or omnivores, protein intake is one of our main daily food concerns. But how much do we actually need every day to maintain a healthy lifestyle? As long as we eat enough calories of whole plant foods, we don’t have to worry at all, we only need 0.8-0.9 grams of protein per kilogram of healthy body weight. In other words, a sandwich with jelly and peanut butter could get you to a third of the way.”



Autore dell'articolo: GG

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