What do people mean when they say a food isn’t a “complete” protein? I.e. quinoa

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What do people mean when they say a food isn’t a “complete” protein? I.e. quinoa

In: Biology

ln order for a food to be a “complete” protein it has to have the 9 essential amino acids (lysine, leucine, etc.). Complete proteins are just types of proteins that contain the necessary levels. Quinoa would actually be considered a complete protein. You don’t have to necessarily eat meat to get complete proteins you can consume dairy and/or tofu.

There are several essential amino acids that we need but our body can’t produce (histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine). So we need to eat them. A food that has some but not all of them is called an *incomplete protein* because we would need to eat it along with another food which has the missing amino acids in order to receive all of the essential amino acids in our diet.

It’s basically marketing fluff for foods like meat (which are *complete proteins* because they contain all 9 essential amino acids) as a way of implying superiority over vegetarian protein sources.

It’s easy to combine two *incomplete proteins* so that together you are taking in all of the essential amoino acids. Here’s some examples:

* Rice and beans

* Peanut butter sandwich

* Hummus and Pita

* Lentils and Barley soup

In order to get a sufficient amount of amino acid each day, how much of a compete protein per day do you need?

It’s a weirdly persistent myth.

So there was this book written in 1971 called Diet for a Small Planet. Think Captain Planet encourages vegetarianism. And to demonstrate the viability of protein in a vegetarian diet, the author uses pork as a reference for “complete protein,” and talks about how to get the same amino acid profile (the building blocks of protein) from a vegetarian diet. When you look at animal protein vs plant protein, plants tend to either be low in the amino acid lysine or methionine. This is where the idea of combining breads and grains with legumes, nuts and seeds in the same meal to meet that profile. “Complete protein” plant foods are high in both.

Here’s the thing: it’s all bullshit. It A) presumed that pig meat is what you need to live/need to emulate, and B) it did not understand protein metabolism. You don’t need to combine protein at the same time. And as long as you don’t have special dietary needs and aren’t eating complete junk, if you’re getting enough calories, you’re getting enough protein too.

The author herself made a retraction of the whole combining protein thing in one of the anniversary editions of her book:

>”In 1971 I stressed protein complementarity because I assumed that the only way to get enough protein … was to create a protein as usable by the body as animal protein. In combating the myth that meat is the only way to get high-quality protein, I reinforced another myth. I gave the impression that in order to get enough protein without meat, considerable care was needed in choosing foods. Actually, it is much easier than I thought.

>”With three important exceptions, there is little danger of protein deficiency in a plant food diet. The exceptions are diets very heavily dependent on [1] fruit or on [2] some tubers, such as sweet potatoes or cassava, or on [3] junk food (refined flours, sugars, and fat). Fortunately, relatively few people in the world try to survive on diets in which these foods are virtually the sole source of calories. In all other diets, if people are getting enough calories, they are virtually certain of getting enough protein.”[3] — from Wikipedia

Despite the fact that this has been debunked for *decades*, when I took a collegiate nutrition course ~10 years ago, my professor — a Registered Dietitian — *still* went through a unit on combining protein.

TL;DR it’s the idea that you either have to combine grains with nuts or legumes to get a “complete protein,” which was arbitrarily based on pork rather than some metabolic requirement, and it’s been thoroughly debunked and retracted by the original author.

Edit: Getting downvotes on the only complete and correct answer, I will [have to remember this](https://en.wikipedia.org/wiki/Gell-Mann_amnesia_effect)