That's what one guy has been trying out see here
The guy is eating nothing but 20 potatoes per day.
After 30 days Voigt’s health markers changed drastically:
Weight – 197 to 189 lbs
Total cholesterol – 214 to 162 mg/dl
HDL (good) – 45 to 46 mg/dl
Triglycerides – 135 to 100 mg/dl
Blood Glucose – 104 to 92 mg/dl
It only takes 11 potatoes to meet the RDA for all amino acids, and 13 to meet the RDA for protein (calculated using a white, baked potato and with a 10% buffer for vegetable protein).
Just goes to show often foods themselves aren't the problem, just preparation & total calorie intake.
I don't recommend eating only potatoes as a dietary idea, but eating some things like potato shouldn't be too bad (just be aware of how you prepare them & your overall calorie intake)