Peanuts are one of the best plant-based sources of protein.
As we’re about to see, it’s not quite a complete protein, but it’s very close. If someone were to eat nothing but peanuts as a protein source, it certainly wouldn’t be the worst choice.
Let’s look at the amino acids in peanuts, and see which ones they lack.
Table of Contents
Essential Amino Acids in Peanuts
The table below was obtained using data from the USDA’s food database for 100 grams of peanuts.
Note that amino acid data will vary based on the type of peanut (i.e. Runner, Virginia, Spanish, Valencia), and even based on a particular crop yield.
Essential amino acids are marked with an asterisk (*) in the table. Every other amino acid is non-essential, which means the body can make it using other amino acids if needed.
| Amino Acid | Amount (g) | Peanut Protein % |
|---|---|---|
| Alanine | 1 | 3.9 |
| Arginine | 3.01 | 11.9 |
| Aspartic acid | 3.07 | 12.1 |
| Cysteine* | 0.323 | 1.3 |
| Glutamic acid | 5.26 | 20.7 |
| Glycine | 1.52 | 6.0 |
| Histidine* | 0.637 | 2.5 |
| Isoleucine* | 0.886 | 3.5 |
| Leucine* | 1.63 | 6.4 |
| Lysine* | 0.904 | 3.6 |
| Methionine* | 0.309 | 1.2 |
| Phenylalanine* | 1.31 | 5.2 |
| Proline | 1.11 | 4.4 |
| Serine | 1.24 | 4.9 |
| Threonine* | 0.863 | 3.4 |
| Tryptophan* | 0.245 | 1.0 |
| Tyrosine | 1.02 | 4.0 |
| Valine* | 1.06 | 4.2 |
If you add up all those values, you’ll see that peanuts have just over 25 grams of protein per 100 gram serving, which is quite high for a plant.
Are Peanuts a Complete Protein?
The concept of a complete protein is mainly for places with poor food reliability. It’s a question of whether someone could be healthy if they only had a limited amount of one particular protein source.
It’s not a serious concern for most people these days fortunately, but there are some places around the world that it can matter.
There are a few different definitions, but I’ll be using the WHO’s definition in the table below to determine whether peanuts are a complete protein or not.
While peanuts have enough raw protein overall, the main question is whether it contains the right percentages of essential amino acids.
| Amino Acid | Complete Protein (min %) | Peanut Protein % |
|---|---|---|
| Histidine | 1.5 | 2.5 |
| Isoleucine | 3 | 3.5 |
| Leucine | 5.9 | 6.4 |
| Lysine | 4.5 | 3.6 |
| Methionine+Cysteine | 1.6 | 2.5 |
| Phenylalanine | 3 | 5.2 |
| Threonine | 2.3 | 3.4 |
| Tryptophan | 0.6 | 1.0 |
| Valine | 3.9 | 4.2 |
As you can see, peanuts are not a complete protein by the WHO’s definition, but are very close.
They are relatively low in lysine by a small amount, but easily have more than enough of every other essential amino acid group.
While peanuts are low in methionine, it’s always considered alongside cysteine since most methionine is used to make cysteine in the body.
Which Foods Pair Best With Peanuts to Form a Complete Protein?
As we saw, peanuts are a bit low in lysine, so it would make sense to eat other foods rich in lysine throughout the day.
However, just about all plants are low in lysine, and peanuts actually have the most lysine of any nut. They are actually one of the top vegan sources of lysine overall, the only ones that are better are:
- Seaweed
- Pumpkin seeds
- Hemp seeds
- Pistachio nuts
- Vital wheat gluten
- Chia seeds
Is this a problem?
The importance of eating only complete proteins is largely a myth for most people with reasonable access to food. Most people have ample access to get enough protein from multiple sources, which almost always ensures that their bodies will have access to all the amino acids they need.
It’s not something that the vast majority of people need to worry about.
