No, Not All Plant Proteins Are Incomplete
Have you ever been told that plant proteins are not complete and that you need animal protein? We dismantle the myth (which has been obsolete for years).
I’m sure we’ve all heard, or even studied, that plant proteins are not “complete,” that only animal proteins are, and that they have to be combined with each other. In fact, it is a myth that lives on, despite being obsolete for decades.
People, even health workers, continue to be surprised by this issue, so we are going to dedicate a few lines to it. But first, some basics.
What are proteins and what are they for?
They are nitrogenous substances composed of chains of amino acids that have several functions, the maintenance of body tissues being the best known . Although they are also part of the immune system and of many enzymes, they carry out transport functions for other substances and can even be used as an energy substrate, although our body prioritizes carbohydrates for this.
And what is an amino acid?
An amino acid is each of the pieces that make up a protein. Imagine that a protein were a train: each car would be an amino acid. So we could build trains with many cars, few, with first-class and tourist-class cars, with freight cars… all depending on what we need the train for. Well , proteins work anyway, each one is made up of different amino acids and in different amounts.
What is a “complete protein”?
We call “complete protein” that which has all the essential amino acids in its composition in sufficient quantities.
The essential amino acids are those that our body is not able to synthesize by itself and must obtain them from the diet. Those amino acids are: histidine, phenylalanine, isoleucine, leucine, lysine, methionine, threonine, tryptophan, and valine. Other amino acids may also be essential in certain situations, but this is not today’s topic.
What plant foods have complete proteins?
The soybean, the chickpeas, some types of beans, the pistachios, the quinoa, the hemp seeds or amaranth have “protein complete.” Also spinach, although the amount they contain is low, about 3g per 100g, per what we would have to eat a large quantity to obtain a remarkable protein ration, and it does not seem very practical.
Therefore, we must not only take into account the quality of the protein, but also the quantity per serving of consumption. And there would still be another concept to value, which is digestibility, but we will leave it for another article.
This information on the aminogram of foods can be consulted in different sources, one of the most accessible is the USDA food composition tables.
Don’t the rest of plant foods have essential amino acids?
Of course they have, all foods have. What happens is that some of them fall a little short.
For example, of the legumes that we have not mentioned before, such as lentils, they have a little less methionine than the rest of the essential amino acids (we say they are “limiting in methionine”); cereals, for their part, are limiting in lysine and threonine, and vegetables are usually limiting in methionine and cysteine.
When we join limiting foods in different amino acids, they complement each other and we get complete proteins again, with all the essential amino acids in sufficient quantities. Hence the theory of combining plant foods to obtain complete proteins.
Do you always have to combine them?
No. Eating lentils with rice is just as effective as eating rice and having lentils for dinner.
Our body has an “amino acid pool”, a kind of reservoir in the liver. In it they are stored and removed as they are needed.
For this reason, it is not necessary to make combinations of foods in the same plate, not even in the same meal to ensure “complete proteins”. It is a myth that should be more than overcome.
