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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