What essential amino acids are missing from plant based protein?

missing essential amino acids

What are essential amino acids?

All the essential amino acids must be consumed in the right proportions for the body to function correctly. The protein found in meat, fish, poultry, eggs and dairy, which are all animal-based protein sources, is very similar to the protein that you find in your body. There are a total of 20 amino acids. These 20 amino acids make up protein in different combinations and ratios. Of the 20 amino acids, nine are essential to your body. It is almost always possible to make the other 11 amino acids within the body (except in certain rare diseases or disorders). There are many examples of complete proteins such as meat, fish, milk, and eggs, all containing large quantities of all 9 essential amino acids. Our bodies can utilize these complete proteins to their fullest ability. They contain essential amino acids, which are helpful when it comes to repairing tissue-forming hormones, enzymes, neurotransmitters, among other things. However, many plant-based eaters such as vegans and vegetarians don’t have complete protein sources and all the essential amino acids.

What essential amino acids are missing from plant based protein?

Plant proteins are typically lacking in lycine, tryptophan, methionine, and isoleucine. The level of these essential amino acids can vary between different plant protein sources. In the same way that animal-based protein sources can differ in their amino acid profile, so can plant-based protein sources. But as a general rule of thumb, most plant-based proteins lack sufficient amounts of lysine first and foremost. 

Because of this inherent lack of certain essential amino acids, people who eat a plant-based diet need to pay close attention to their protein intake and should include a wide variety of different plant based protein sources in their diet. Researchers show that plant based vegetarians and vegans who consumed a varied plant protein diet had no essential amino acid deficiencies.[1]

Why is it harder for plant based eaters to get all the essential amino acids?

The main reason plant-based diet followers have a hard time getting all the essential amino acids is that we as humans are made up of muscle. You could think of it in another way we are all made up of meat, the same thing that meat-eaters consume. So it stands to reason that if you are eating the same thing you are made of, you will be getting all the nutrients and amino acids you need in the proper quantity and ratios. We are not plants, so when we eat plants, they are inherently lacking certain nutrients amino acids in the proper quantity and ratios that the body needs. This lack of amino acids is not a knock against plant-based diets. It is just a reality and one that people have to acknowledge and workaround.

Lysine and Methionine content in plants

The table below shows the lysine and methionine percentages found in certain plants. We have included the percentage content of these amino acids found in eggs to compare how low the amino acid content is in the plant sources.[2]

Food SourceMethionine PercentageLysine Percentage
Table showing Methionine and Lysine percentage of plant protein sources

Summary of what essential amino acids are missing from plant-based protein.

As you can see from the table listed above, plant-based protein sources are indeed lacking in certain essential amino acids, but they still do contain these essential amino acids. So plant-based eaters can get all the essential amino acids their bodies need. They have to be mindful of their plant-based protein choices and add various plant protein sources to ensure they get all the essential amino acids in sufficient quantities. Plant-based eaters need to focus on key essential amino acids such as lysine and methionine. These are the two amino acids missing or are in low percentages in plants most commonly.


  1. Dietary Protein and Amino Acids in Vegetarian Diets—A Review (nih.gov)
  2. Essential amino acids compositions for some seed and leafy plantsa. (A)… | Download Scientific Diagram (researchgate.net)