I remember learning about the Great Famine in Ireland growing up where people were forced to live mostly on potatoes for a period of 7 years.
Spoiler alert: About 1 million people died, so I wouldn’t recommend adopting a similar diet.
But it probably wasn’t from a lack of protein, as I’m about to show you. I’ve summarize nutritional data on white potatoes and sweet potatoes from the USDA so we can look at their amino acid profiles.
Table of Contents
Essential Amino Acid Profiles of Potatoes
The table below looks at what percent of the protein in potatoes is composed of each essential amino acid (the ones your body can’t make).
The second column has the minimum percentage defined by the World Health Organization (WHO). These values have shifted a bit over time, so they are no means set in stone, but still a nice reference.
| Complete Protein (min %) | White Potato protein (%) | Sweet Potato protein (%) | |
|---|---|---|---|
| Histidine | 1.5 | 1.67 | 1.87 |
| Isoleucine | 3 | 3.24 | 5.03 |
| Leucine | 5.9 | 4.76 | 7.37 |
| Lysine | 4.5 | 5.19 | 4.91 |
| Methionine+Cysteine | 1.6 | 2.71 | 3.27 |
| Phenylalanine+Tyrosine | 3 | 6.29 | 10.12 |
| Threonine | 2.3 | 3.24 | 4.97 |
| Valine | 3.9 | 5.00 | 6.55 |
In terms of protein composition, both white and sweet potatoes exceed the minimum percentage of almost all essential amino acids.
The only shortcoming is that the percentage of leucine in white potatoes is a bit under the guideline.
Amount of Each Amino Acid in Potatoes
The other part of a “complete” protein is whether or not there’s a large enough quantity of each essential amino acid.
It doesn’t matter if the percentages are great if there’s essentially 0 protein in total.
The data in the table for white and sweet potatoes is per 100 gram serving of baked potato. Here are some general weights of potatoes for comparison:
- Small potato – 138 grams
- Medium potato – 173 grams
- Large potato – 299 grams
Obviously these will vary in real life.
| Needed per day (mg for 65 kg adult) | In 100g White Potato (mg) | In 100g Sweet Potato (mg) | |
|---|---|---|---|
| Histidine | 650 | 35 | 32 |
| Isoleucine | 1300 | 68 | 86 |
| Leucine | 2535 | 100 | 126 |
| Lysine | 1950 | 109 | 84 |
| Methionine+Cysteine | 975 | 57 | 56 |
| Phenylalanine+Tyrosine | 1625 | 132 | 173 |
| Threonine | 975 | 68 | 85 |
| Valine | 1690 | 105 | 112 |
At first glance, these quantities aren’t very impressive.
However, note that there’s about 100 calories in this size of serving. So it is technically possible to eat say 2,500 calories of potatoes and reach the minimum quantity of all essential amino acids.
Are Potatoes a Complete Protein?
Technically, you can get all of your essential amino acids from potatoes, you would just have to eat a lot of them.
In that sense, you can argue that potatoes are complete proteins.
Are they a practical main protein source for most people? No, but potatoes are certainly fine foods to include in a healthy diet.
Could You Live Off of Just Potatoes?
While you can get enough protein and essential amino acids from potatoes, you need more than that to live healthily.
You also need to consider essential vitamins, minerals and fats as well.
Potatoes do have an impressive amount of nutrients, but still have very little:
- Essential fatty acids
- Vitamin A, E, and B12
- Calcium
- Zinc
- Selenium
In short, someone could probably live off of potatoes for a while, but it would not be sustainable long term as stores of vitamins, minerals, and essential fats ran out. That might not kill them, but it would result in negative health consequences.
