Saturday, April 26, 2008

"If All You Ate Were Potatoes, You'd Get All Your Amino Acids"

Doug asked:
"I still don't understand why more care isn't necessary to avoid deficiencies of the essential amino acids. Is it the case that these amino acids are present in all fruits and vegetables? (I didn't think this was so, but you mentioned on that other thread that thinking has changed in this regard.) Or is it simply that easy to avoid a deficiency of an essential amino acid by consuming any mixture of fruits and vegetables?"
I would answer "Yes" to Doug's last question. I thought it summed up the facts well.

Plants are capable of manufacturing all 20 amino acids, which include the essential amino acids (EAAs), although amounts vary. I checked a number of foods (potatoes, broccoli, tomatoes, asparagus, corn, rice, oatmeal, beans, and others) and found all EAAs in each of these foods. Even an apple which is listed as having 0 grams of protein has all the EAAs, albeit in small amounts.

Since I said in an earlier comment, "No mixing of foods is necessary. If all you ate were potatoes, you'd get all your amino acids," I felt obliged to back it up. Below is my back-up.
  • The first column lists all 8 EAAs for adults.
  • The second column lists the World Health Organization's recommended intake per body weight.
  • The third column lists the specific RDI for a 120 lb adult.
  • The fourth column lists the amount of each AA in a medium potato, with skin.
  • The fifth column lists the amount of each AA in 5 medium potatoes.
  • The last column lists the % of recommended intake (for a 120 lb adult) for each AA when 5 potatoes are consumed.

Click for larger.
- The WHO's recommended intakes represent the minimum amount for an individual with the highest need, multiplied by a factor of 2 for safety.
- Methionine + Cysteine = Total Sulfur Amino Acids
- Phenylalanine + Tyrosine = Total Aromatic Amino Acids
- WHO: World Health Organization
- EAA: Essential Amino Acid

For a 120 pound adult, five potatoes (960 calories) supply over 100% of the recommended intake for all essential amino acids. They also supply 25 grams of total protein.

It's pretty difficult for an adult to eat a plant-based, vegetarian diet that doesn't provide all EAAs, as long as caloric needs are met.

Finally - The pool of AAs that our body uses to manufacture its own proteins isn't limited by what we eat. Normal daily turnover of our cells provides a substantial pool from which to draw amino acids. Bacteria that line our colon also manufacture AAs, including EAAs, that we can utilize.

It is a misconception that plants provide "incomplete protein", regardless of what Ms. Lappe advanced in her 1971 book, "Diet For A Small Planet."
Photo: Homegrown. Me and my potatoes.


Anonymous said...

Add quinoa :-)

Anonymous said...

This is extremely interesting. Thank you for posting this! Are these the EAA amounts in waxy potatoes, starchy potatoes, or "average" potatoes?

Could you please create similar tables for sweet potatoes, and also for 100% whole wheat bread? (this FAO web page has information on EAA content of sweet potatoes but it is given in terms of mg N/g, which I doubt is equivalent... or even convertible... )

Bix said...

I would actually like to do that. Perhaps a future post. In the meantime, you can go to

It will give you the amino acid breakdown for just about any food.

Jess said...

I'm commenting on a really old post, but this is fascinating! I'm vegan and always make a point of eating a wide variety of pulses and grains to make sure I get all the EAAs - I had no idea that potatoes provided all of them in good proportions!

I guess I can stop spending precious student finance pennies on quinoa and keep munching the home-grown potatoes my parents give me :)

dogma said...

Thank you for this handy little table :)

I'd heard that the Irish did all right on potatoes and milk before the famine, but I didn't know potatoes could go so far on their own.

Tariq Hossenbux said...

Interesting post. I tried the vegetarian diet for a week and did find myself a little tired. Could have been psychological though expecting myself to be more tired on the vegetarian diet.