Potatoes are healthy to eat and are low in calories.
Potatoes are good source of Vitamin C as well as B6 and Manganese, pantothenic acid, niacin and phosphorus.
When potatoes become unhealthy to eat is when you deep fry the potatoes as french fries or just plain fried potatoes.
Mashing potatoes and baking potatoes are much healthier for your health but just don't put too much butter on the potatoes otherwise you risk raising your cholesterol levels.