A completely vegan complete protein
(plant protein just as good as from meat)
What is protein?
Protein is a type of a biomolecule that is a polymer of 20 different amino acids. Even though proteins are found in every living cell and perform many different functions, most people focus on the dietary protein that is good for building and maintaining our muscles. Of the 20 amino acids that make up proteins, humans can make 11 of them (non-essential amino acids) and we have to consume 9 of them (essential amino acids) from our food sources.
What is a complete protein source?
A complete (dietary) protein has the same ratio of amino acids as the human muscle. Since other animals are very similar to us (evolutionarily), their meat has a very similar amino acid profile to ours, with beef, lamb, and pork having the closest ratio, since they are all closely related mammals. Therefore, meats would have a “complete protein”. On the other hand, while every single plant has all 20 amino acids, their ratio is not the same as in humans. Therefore, we would need to eat a lot more of plant protein to get the same benefit as from animal protein.
Real life examples for incomplete protein
Assembling bicycles
You want to assemble bicycles, so you order components. A company ships bicycle components in boxes, where one box includes:
- 3 front wheels
- 3 rear wheels
- 3 frames
- 1 handle bar
- 3 seats
How many bicycles can you assemble from each box?
Only 1, because the handle bars are the limiting factor. To assemble 3 bicycles, you would need to order 3 boxes of parts, then dispose of the excess parts. This is exactly what our bodies do with plant-based protein - we utilize the amount of amino acids that have the right ratio, then waste the rest of them.
Getting complete protein from soybeans (tofu, soy milk…)
If you look at the graph above, you will see that soybeans have about ~40% of methionine that beef has. This is the handle bar of soybeans (from the bicycle example above). To get the same amount of complete protein from soybeans, you would need to eat 2.5 times more total protein from soybeans than from beef. That may be OK for some people, but not for all (it may be too many calories, some people don’t like tofu/soybeans that much…).
How to get complete protein from plants?
There is an easy way to get complete protein from soybeans. Whether you eat tofu, drink soymilk, or buy soybean protein isolate, all you have to do is:
1. Supplement it with methionine, histidine, and lysine.
2. Consume 20% more total protein from soy (to compensate for the next limiting amino acid, valine)
How much methionine, histidine, and lysine to supplement?
As per the references below, for each 100 grams of total protein, you need to add the difference between beef and soybean. An easy way to do this is:
- Purchase methionine, histidine, and lysine amino acids.
- Make the amino acid mix (AAM): 1.82 parts methionine, 1.25 parts histidine and 2.33 parts lysine. Store in a jar on a shelf.
- Add 5.4 g of AAM per 100 g of soy protein, to make it nearly equal to beef protein. If you don’t have a scale, 1 tablespoon of AAM = 7 g.
A real example: You want to use a pound of firm tofu. It has 5 servings with 7 grams of protein per serving, for 35 grams of total protein. You will need to add 1.9 g of AAM to make it “nearly” complete. If you use a pound of extra firm tofu, which has a total of 70 grams of protein, you will need to supplement with 3.8 g of AAM.
A super tasty vegan yogurt with complete protein — my recipe.
Can I supplement soybean protein with wheat to make it complete?
In my opinion, this would be very unreliable, given the large diversity of wheat strains whose content of methionine, lysine, and histidine can vary by several fold (see the reference below). If we ever get to a point where the source of wheat you are using is profiled for amino acid content, natural complementation will be possible.
Assumptions
- Amino acid ratios in beef is the closest to human (I could not find a reference that states what is the perfect amino acid ratio for building human muscle)
- Amino acid ratios are the same in tofu, soymilk and soybeans (need to do more research on this)
- The strain of soybeans you and I buy at the store have the same amino acid profile as in the publication used to make all the calculations here.
References
https://academic.oup.com/jas/article/94/6/2603/4702294
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5302255/
https://www.mdpi.com/2076-2615/10/12/2272
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6769807/
https://www.frontiersin.org/articles/10.3389/fnut.2020.00141/full