No, the nutrients in potatoes and apples aren’t all in the skin

Everyone has some sage piece of food-related wisdom a parent, grandparent or another family member told them as a child. We often take those little nuggets of advice or warnings as gospel, never really considering whether they’re true, even as we grow older.

But some of this food folklore is nothing more than myth. That’s what one viral post implied about the belief that all of the nutrients in potatoes and apples are found in the skin.

Is that just a lie parents tell their kids so they eat their whole potato or apple, or is there some truth to it?

THE QUESTION

Are all of the nutrients in potatoes and apples found in the skins?

THE SOURCES

• Harvard T.H. Chan School of Public Health
• U.S. Department of Agriculture (USDA)
• Cleveland Clinic
• Idaho Potato Commission
• Potatoes USA, the American potato industry’s marketing and research organization
• United Kingdom’s Agriculture and Horticulture Development Board
• Bwalya Lungu, Ph.D., food science and food folklore professor at the University of California Davis

THE ANSWER

No, not all of the nutrients in potatoes and apples are found in the skins. Even so, there are a lot of nutrients in the peel.

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WHAT WE FOUND

Fruit and vegetable skin — like those found on an apple or potato — contain a lot of nutrients, but so does the flesh of these foods. Eating the entire potato or apple, including the skin, allows you to get the most nutrients possible, but you’ll still consume a healthy, nutrient-rich food if you eat either.

Apples

While nutrients are spread throughout an apple, some nutrients are more prominent in the skin, while other nutrients are more prominent in the flesh.

The skin holds much of the fiber and flavonoids, which are naturally occurring chemicals with various health benefits, while the flesh holds most of the vitamin C, according to Harvard T.H. Chan School of Public Health. 

Data from the U.S. Department of Agriculture (USDA) show this well. If you were to eat 100 grams of a raw apple with skin, you’d get about 2.4 grams of dietary fiber. If you were to eat 100 grams of a raw apple without skin, you’d get about 1.3 grams of dietary fiber.

The apple with skin has 4.6 milligrams of vitamin C, but the apple without skin still has 4.0 milligrams of vitamin C. You’d get about 107 milligrams of potassium in an apple with skin, but you’d still get 90 milligrams of potassium if you ate your apple without its skin. You only lose 1 milligram of calcium and magnesium alike if you decide to peel the apple.

Potatoes

The nutrient breakdown is similar for potatoes. 

The skin of a russet potato, a potato commonly used for baking, has about half of the potato’s fiber, according to the Idaho Potato Commission.

“But if you look at potatoes as a whole, you will find that the majority of your potassium and your vitamin C is actually found in the flesh and not in the skin,” said Bwalya Lungu, Ph.D., who teaches food science and food folklore at the University of California Davis.

The flesh of a potato isn’t just high in potassium and vitamin C, it’s higher than other foods people typically think of as being nutrient-rich. For example, the Cleveland Clinic says a potato has more potassium than a banana, and more vitamin C than an orange.

Potatoes USA, the American potato industry’s marketing and research organization, confirms this.

“While the skin does contain approximately half of the total dietary fiber, the majority of the nutrients are found within the potato itself,” Potatoes USA says.

Potatoes USA says a typical medium potato contains 2 grams of fiber with its skin, and 1 gram of fiber without its skin. A typical medium potato with the skin contains 620 mg of potassium and 27 mg of vitamin C, but it only loses about 150 mg of potassium and 4.5 mg of vitamin C when you remove the potato’s skin.

Even so, potato skins aren’t just good for fiber. A 2007 study by researchers at Oregon State University’s Hermiston Agricultural Research and Extension Center found that vitamin B9, also called folate, is 30% more concentrated in the skin of a typical potato than it is in the flesh.

USDA data backs this up. The skin alone of a salted baked potato has 22 micrograms of folate. The flesh and skin of a salted baked potato have a combined 28 micrograms of folate.

Cooking

There is a situation where keeping the skins on your potatoes does make a big difference in how nutritious they are: when you boil them.

Lungu says that boiling potatoes with the skin on minimizes the loss of the potato’s vitamins and minerals that occurs when food is cooked.

“If you peel them, they lose some of [the potato’s vitamins and potassium],” Lungu said. “And sometimes those numbers can come down from anywhere to 50 to 80%.”

The United Kingdom’s Agriculture and Horticulture Development Board also recommends leaving potato skins on before boiling any potatoes. “This ensures that the nutrients and flavours are not lost during cooking and you get all those lovely vitamins, too,” it says.

But, again, potatoes are still plenty nutritious even if you do choose to boil them without the skin.

“The question is, are you losing everything to the point that it's going to be detrimental to your health?” Lungu said. “I don't think so.”

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