Potatoes are underground tubers that grow on the roots of the potato plant, Solanum tuberosum. This plant is from the nightshade family and related to tomatoes and tobacco.
Cooked potatoes with skin are a good source of many vitamins and minerals, such as potassium and vitamin C.
Aside from being high in water when fresh, potatoes are primarily composed of carbs and contain moderate amounts of protein and fiber — but almost no fat.
Potatoes are mainly composed of carbs, primarily in the form of starch. The carb content ranges from 66–90% of dry weight.
Simple sugars — such as sucrose, glucose, and fructose — are also present in small amounts.
Potatoes usually rank high on the glycemic index (GI), making them unsuitable for people with diabetes. The GI measures how foods affect your rise in blood sugar after a meal.
Cooling potatoes after cooking may lessen their effect on blood sugar and lower their GI by 25–26%.
Even though potatoes are not a high-fiber food, they may provide a significant source of fiber for those who eat them regularly.
The level of fiber is highest in the skin, which makes up 1–2% of the potato. In fact, dried skins are about 50% fiber.
Potato fibers — such as pectin, cellulose, and hemicellulose — are mainly insoluble.
They also contain varying amounts of resistant starch, a type of fiber that feeds the friendly bacteria in your gut and improves digestive health.
Resistant starch can also improve blood sugar control, moderating your rise in blood sugar after meals.
Compared to hot potatoes, cooled ones offer higher amounts of resistant starch.
Potatoes are low in protein, ranging from 1–1.5% when fresh and 8–9% by dry weight.
In fact, compared to other common food crops — such as wheat, rice, and corn — potatoes have the lowest amount of protein.
However, the protein quality of potatoes is very high for a plant — higher than that of soybeans and other legumes.
The main protein in potatoes is called patatin, which may cause allergic reactions in some people.
Vitamins and Minerals
Potatoes are a good source of several vitamins and minerals, particularly potassium and vitamin C.
The levels of some vitamins and minerals drop during cooking, but this reduction can be minimized by baking or boiling them with the skin on.
- Potassium. The predominant mineral in potatoes, potassium is concentrated in the skin and may benefit heart health.
- Vitamin C. The main vitamin found in potatoes, vitamin C is significantly reduced with cooking — but leaving the skin on appears to reduce this loss.
- Folate. Concentrated in the peel, folate is mostly found in potatoes with coloured flesh.
- Vitamin B6. A class of B vitamins involved in red blood cell formation, B6 is found in most foods. Deficiency is rare.
French Fries and Potato Chips
Fried potatoes and potato chips may also contain acrylamides, glycoalkaloids, and high amounts of salt, which all may be harmful over time.
For this reason, high consumption of fried potatoes — especially french fries and chips — should be avoided.