Soy Protein Amino Acid Profile


The following graph shows a typical soy protein amino acid profile. There’s a little asterisk next to the names of essential amino acids.

soy protein amino acid profile

(Data Source)

This graph was made with our amino acid profile comparison tool.

It might be easier to read in table form. Essential amino acids are again marked with an asterisk (*).

  % of total amino acids
Alanine 4.5
Arginine 6.1
Aspartic Acid 13.1
Cystine 1.9
Glutamic Acid 18.6
Glycine 4.5
Histidine* 4.7
Isoleucine* 2.8
Leucine* 6.8
Lysine* 8.7
Methionine* 2.6
Phenylalanine* 4.5
Proline 4.2
Serine 6.8
Threonine* 2.3
Tryptophan* 0.2
Tyrosine 4.7
Valine* 3

Overall Summary of Soy Protein’s Amino Acid Profile

There are a few points of note in the data above.

First, soy has very low levels of tryptophan, which is an essential amino acid. But as long as you have other protein sources, it’s not a big deal.

For example, pea protein’s amino acid profile is relatively high in tryptophan. Here are other good vegan sources of tryptophan.

Similarly, like all beans, soybeans have a low amount of methionine, it’s one of the hardest amino acids for vegans to get. Still, there are plenty of good methionine sources for vegans if you pay attention to it.

Finally, soy has relatively high levels of a different essential acid – histidine. It has a relatively higher percentage than even whey does.

Overall, soy is a complete protein source with a well balanced amino acid profile.

About the author

Dale C.

Your friendly neighborhood vegan from Toronto. Chemical engineer turned semi-professional soccer player and freelance writer. Trying to do my small part in making the world better by writing about the wonderful world of veganism.


  • Hi!

    I can’t access your numbers, but they seem wrong judging by other sources. Especially the Methionine content seems off. See e.g. 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.