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The “complete protein myth”

First of all, I kind of despise the term “complete protein”. It more reminds me of a term coined by the meat industry than an actually useful phrase. It is so often used in pseudo-scientific pieces and the concept is mostly either misrepresented or just used to spread unnecessary fear.

A “complete protein” would be a protein that contains all essential amino-acids – and for what it's worth, every living organism contains “complete proteins”. You would only get “incomplete proteins” when looking at isolated extracts of organic matter – like Gelatin. So, as the discussion about “complete proteins” should more be an academic one, lets pretend that this term doesn't exist for now...

What's the value of it all?

Let talk about “biological value” (BV) instead – which I have seen often being confused with “complete proteins”. OK, they have some fundamental concept in common, but they are not the same. The general idea behind “biological value” could be paraphrased as:

How much of the protein from a SINGLE food source can be utilized and transformed into body protein.

Maybe a very simplified example can make this clearer:

Let's say you need to produce a protein from the amino acids A, B & C. The protein that we want to build will be something like “A-B-C”. Now, if we would eat something with an amino acid composition of AAA-BBB-CCCC, we could build THREE “A-B-C” proteins from that and are left with an unused “C” amino acid to discard.

So not all the protein mass in the food source can be turned into body protein, as the proportion of the individual amino acids in our food source is not 100% aligned perfectly with our body's protein needs. But we can still synthesize an amount of needed protein from the source: We were able to utilize 90% of the source protein but can't use the remaining 10% (the last “C”).

In our example, the biological value would be 90, as the composition of the source protein does match well with our needs, but is not perfect. (Too much “C”)

Even though this protein source wouldn't be “perfect”, it doesn't need to be. By simply consuming more of that protein source any amino acid demand could be satisfied to build any needed amount of body protein.

(And a truly “incomplete protein” could be something like eating “AAAA-CCC” – because you can't produce a single “ABC” from such a source. It has a BV of 0)

Don't strive for perfection ...

Well, if we define “biological value” like that, what would be the “perfect protein” source? No, not eggs, not beef – it would be other humans.

The amino acid composition of a human body matches pretty much perfectly the needed composition to grow another human. Humans therefore would have a classical biological value of 100. However, it would be kind of crazy to perform clinical trials with a cannibalistic control group, so they came up with another reference point: eggs.

Using eggs as a reference point is pretty much arbitrary. They could have normalized the scale in reference to a piece of cardboard or a cucumber, but they chose eggs. On the other hand, they are pretty easy to come by (if you don't mind the exploitation of the chicken), they are neatly packaged and they have a high protein content. After this arbitrary decision for a reference point, “eggs” now have a biological value of “100” and is now expressing the utilization relative to the utilization of egg-protein. That scale isn't exactly good or bad – it just “is”.

“100” isn't even the the top end of the scale, as you can achieve values of above 100 because eggs are not a “perfectly composed amino acid source” themself. E.g. combining potatoes and eggs would give us a BV of 136, or soy and rice gives 110.

Combination is key

And this leads us to a key insight: Combining foods generally INCREASES the biological value.

For example: Food X has the composition “AAA-BB-CC” – Food Y has “A-BB-CC”. Both foods individually have a suboptimal BV, but in combination, they would be perfect, as you could build four “ABC”s from them with no amino acid wasted.

Basically every naturally occurring food source has proteins – but with slight variations in the amino acid composition. By combining different foods these variations get “leveled out”. That's why the recommendation is to “eat the rainbow” – or eating a varied diet. This is also very much true for a plant based diet. If you eat your fruits, your veggies, your nuts & seeds, your whole grains and your legumes, you are pretty much golden when it comes to the amino acid composition. (So eat your hemp seeds if you like them. :) )

A gram per day, ...

But how much protein do we really need? The rule of thumb would be to eat “1 gram” of protein per kilogram body weight per day. For a 80kg person, that would amount to 80g of protein intake. And if you eat a varied diet that contains all the food groups, it doesn't really matter too much what dishes you would eat – you should end up roughly with the recommended amount. However, if a lot of your calories come from processed foods, then it can get more difficult to hit that target, because e.g. fried stuff has a lot of calories but doesn't contain a lot of the other good stuff.

(And another word on the “recommended protein amount”: People in different situations might have different protein needs. E.g. professional athletes or pregnant persons can obviously have different needs. However, if they are eating a well balanced diet and are not in a caloric deficit (i.e. loosing weight), they should still be mostly fine. In case you are not sure: talk to your doctor or a dietitian!)

Just stay happy <3

And the most important at last: Please do not obsess about protein too much. The “fear” of protein deficiency is something that none of us should have. We (hopefully) all have enough to eat – and that's sufficient for the most part. Just eat good food and you'll be fine.

NOTE: I'm not a doctor nor a dietitian and this article is a strong simplification of the matter presented. If you have issues with your health or need serious advice, please talk to a professional and don't trust random people on the internet! ;)