Soy Protein Amino Acid Profile

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The amino acid profile of any protein source will vary based on the sample use.

The table below is pulled from this study where researchers looked at 44 strains of soybeans throughout Arkansas. It shows the range of each essential amino acid, alongside the amino acid profiles of egg and milk protein.

soy amino acid profile table

In some cases the ranges are quite large, showing that there can be significant variation between beans grown in different places.

Is Soy a Complete Protein?

Let’s look at how the essential amino acids in soy stack up against the ideal distribution of a complete protein (from Wikipedia). Since the units above are in mg/g of proteinwe can just divide by 10 to convert it to a percent.

 Complete Protein (min %)Soy protein (%)
Histidine1.82.7-5.9
Isoleucine2.51.5-4.0
Leucine5.54.4-7.3
Lysine5.14.7-13.8
Methionine+Cysteine2.52.6-10.8
Phenylalanine+Tyrosine4.72.5-5
Threonine2.71.5-4.5
Valine3.21.7-4.2

Soy stacks up really well, it’s a balanced protein source.

There are some strains might be relatively low in certain essential amino acids. However, soy protein is still considered a complete protein since it has a sufficient amount of all essential amino acids.

Soybeans are one of the most nutritionally packed legumes there is. See my bean nutrition comparison for more detail.

About the author

Dale Cudmore

Your friendly neighborhood vegan from Toronto. Chemical engineer turned semi-professional soccer player and freelance nutrition writer. I've been vegan for years and try to make life easier for others by sharing what I've learned.

4 comments

  • Hi!

    I can’t access your numbers, but they seem wrong judging by other sources. Especially the Methionine content seems off. See e.g. https://link.springer.com/article/10.1007/s00726-018-2640-5 Figure 4 Graph B (the one for Methiodine) – it suggests only 0.58% of all the protein in Soy is made up of Methiodine (I did the math with the table of EAA + NEAA provided below this which matches the graph). Your data on the other hand suggests a value of 2.6% which is much higher and also contradicts to what you find when you search for amino acid profiles of soy protein (you will find papers stating that it is especially low in Methionine).

    Could you help me out on this? ^^ I am currently trying to do some protein powder amino acid composition maths. Thanks! 🙂

    • I mean it’s low in either case. The study I referenced looked at 40 strains of soybeans grown in the United States, I find that more convincing than the one you linked. Don’t think it makes a huge difference either way.

  • Thanks for a simple and accurate analysis Dale. VI’s reply is the perfect bs to shed doubt on these numbers.. lobbyist for big meat ag?.. Methionine and Cysteine are nutritionally interchangeable, and the 2.6-10.8% correctly shown is for the combination.

    • It’s a bit of a confusing topic, I’m quite happy to clarify my thoughts on the data when someone raises a potential issue.