I met a british entrepreneur at a party the other week who held himself out as a nutrition expert. When I mentioned to him that I practice a vegetarian diet, he claimed that meat and other animal products are the only foods that have complete protein in them. As I tried to explain to him that he is probably referring to amino acid balance, not presence, he insisted that essential amino acids were missing in all plant proteins including soy. He said he would bet 10,000 British pounds on this. I asked for a bystander to take a video as evidence of the terms of the bet. Here’s a transcript of the recording, A is him. O is me:
A: I bet you that meat has a greater variety of amino acids in it than soya.
O: What does “greater variety” mean for you?
A: It means you need a variety of amino acids in life to be healthy and build quality muscle and a quality that works, and meat has a grater variety of amino acids.
O: So are you claiming that soy and other plants don’t have all the essential amino acids in them?
A: Individually no, they don’t.
O: Actually, every single plant product has all the essential amino acids in them.
A: Individually no, they don’t. I will bet you 10,000 british pounds.
Who is correct, A (he) or O (me)?
Plants contain all essential amino acids. It’s just that some plants contain lower amounts of specific individual amino acids. For example, lentils are considered an “incomplete protein” because they are low in methionine, however they do still contain some methionine (0.2g per 100g).
You are correct. A food being an incomplete protein - as most plant foods are, though exceptions include soy, quinoa, hemp, buckwheat, etc. - doesn’t mean it completely lacks one or more essential amino acids, it means there is a limiting amino acid - that is, one which is present in a lower proportion than the dietary requirement. This graph shows that despite beans and grains not being complete proteins, they do contain all essential amino acids, they just contain relatively lower amounts of methionine and lysine, respectively.
do all plants produce all essential amino acids
No, not all plants produce all essential amino acids. Most plant-based sources of protein are incomplete, meaning they lack one or more of the essential amino acids that the human body cannot produce on its own. However, by combining different plant-based protein sources that complement each other in terms of their amino acid profiles, it is possible to obtain all the essential amino acids in sufficient quantities. Examples of complementary protein combinations include rice and beans, hummus and pita bread, and peanut butter on whole wheat bread.
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