Thanks for taking the time to respond to this “ex-vegan”. I have spent a lot of time looking at the amino acid profiles of plants and wanted to clear up some misconceptions. Specifically, the myth that plants are incomplete protein sources and that you have to carefully pick and choose to get a “complete protein”.

Plants are living organisms that use the same 20 amino acids we do. All of them. It’s true that the levels of different amino acids vary between plants, these variations are not as dramatic as they are made out to be.

Take rice and beans as an example — this happens to be one of the more dramatic cases, and is still overblown. The ‘limiting’ (lowest) amino acid in beans is methionine. The ‘limiting’ (lowest) amino acid in grains is lysine.

If you got all your daily protein (e.g. 60 grams) from beans, you would get nearly twice your daily need of lysine. If all you ate were whole grains (enough to get 60 grams protein), you would get just over 100% of your daily lysine. So, while grains are not as rich as beans in lysine, they are still certainly good enough.

The reverse story is true for methionine. If you ate enough grains to get 60 grams of protein, you would get nearly double your daily needs. If you got all your protein from beans, you would still get just over 100% of your needs. Again, beans are not as rich as whole grains for methionine, but they still get the job done.

Really, there are only two ways to FAIL to meet your amino acid needs — and downstream molecules they are used for. One day I’ll put this into a sarcastic article!

Method 1: Don’t get enough protein.

Option 1: Eat only fruit and oil. Unlike whole veggies and grains, fruits (a specialized plant organ) and oil (processed) have little to no protein.

Option 2: Eat tons of processed foods — they tend to have less protein per calorie because of the added fats and sugars. This is an excellent way to fall short of your protein target of a measly 10% of calories.

Method 2: Only eat a single food — just like potato man. There are specific single foods (such as certain nuts) that would leave you SLIGHTLY short of one amino acid if that were all you ate. For example, if you spent a year eating only almonds, you would be 10–20% short on lysine (the achilles heel of nuts). Still, not a very impressive shortfall for all that work!

For more, check out my article:

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Scientist (PhD Genetics @Stanford) * Mother * Passionate about science-based healthy choices * Lifelong learner * Founder: Fueled by Science

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