Why it’s beneficial to eat the peels and skins of many fruits and vegetables
From the National Geographic, March 26, 2024, by Stacey Colino:
Don’t trash the peels! The skins of fruits and veggies pack a nutritional punch
Studies suggest that certain fruit and vegetable peels are packed with antimicrobial compounds and chemicals that fight diabetes, inflammation, and cancer. Here are several of the most nutritious and tips on how to consume them.
If you remove and discard the peel of most fruits and vegetables, you might be cheating yourself out of a rich source of nutrients, fiber, and phytochemicals—bioactive compounds found in plants.
A study in the journal Current Research in Food Science found that the peels of apples, peaches, and persimmons have higher concentrations of antioxidants (such as gallocatechin, epicatechin, and epigallocatechin) than the flesh or seeds of these fruits. In some instances, the peel of some fruits, including pomegranates, has been shown to have antioxidant levels that are exponentially higher than the inside of the fruit. The potential health effects of consuming peels are so promising that some food manufacturers are enriching functional foods, such as breads and biscuits, with fruit and vegetable peels.
Besides curbing food waste, eating the peels has nutritional benefits because “that’s where the darker color is,” says Keith Ayoob, a registered dietitian-nutritionist at the Albert Einstein College of Medicine in The Bronx. “Colors have power nutritionally because they indicate the presence of antioxidants,” which help protect cells from damage caused by pollutants, ultraviolet rays, and other sources of unstable molecules called free radicals.
Because “the peel is the protective layer on fruits and vegetables, it tends to have concentrated compounds like phytochemicals that serve as defense mechanisms against the sun, rain, and pests,” says Wendy Bazilian, a nutritionist and public health consultant based in San Diego. “Those defense mechanisms support our health, too. When you peel these fruits and vegetables, you’re literally peeling off some of the nutrition.”
That’s not to say you should eat the skin of every fruit and vegetable. Avoid cantaloupe, avocado, and pineapple skin, and always peel onions and garlic. It’s true that edible skins of conventional fruits and vegetables may harbor pesticide residue, which is why it’s important to clean them thoroughly: “Rinse it under clean water and use a vegetable brush or paper towel on the skin,” advises Lisa Young, an adjunct professor of nutrition at NYU. Of course, you should wash organically grown produce, as well, to remove dirt and germs.
Here’s a closer look at how various peels compare nutritionally, with ideas for how to incorporate them into your meals if you don’t eat them naturally:
Apples
When it comes to apples, “the skin is the most nutrient-dense part,” says Joan Salge Blake, a registered dietitian and nutrition professor at Boston University. “It contains 300 percent more vitamin K, 140 percent more vitamin A, and 110 percent more vitamin C.”
Apple skins are also rich in soluble and insoluble fiber and quercetin (a powerful antioxidant), says Bazilian, author of the Eat Clean, Stay Lean series. Plus, she adds, “you have more chews if you eat the skin, which slows down how fast you eat.”
So don’t bother peeling your apples, whether you’re eating them raw, cooked, or baked. For a delicious snack or dessert, bake whole apples in the oven or peel the skin and bake the strips with a dash of cinnamon.
Carrot
The peel of a fresh carrot accounts for only 11 percent of its weight but contains 54 percent of its phenolic acids, which act as antioxidants, research has shown. Carotenoids, vitamin K, niacin, and vitamin C are also more concentrated in the peel than the inside of the carrot.
Simply wash carrots with a vegetable brush and running water and eat them raw or cook them. You can peel the skin into strips and air fry them to make a crispy snack, says Jackie Newgent, a nutritionist and plant-forward chef based in New York City. Or, use “carrot ribbons” from the peeled strips in a carrot salad.
Citrus fruits
Not only do the peels from oranges, grapefruits, lemons, and limes contain higher amounts of vitamin C and carotenoids than the pulp of these fruits, but they’re also rich in a powerful antioxidant called hesperidin, which has anti-inflammatory properties and can help with blood sugar regulation.
Research has found that people in Arizona who regularly consume citrus peel have a 34 percent lower risk of developing squamous cell cancer in the skin. Another body of research suggests that citrus peels can have neuroprotective effects, improving cognitive function in older adults. And a study in a 2023 issue of the journal Molecules found that substances in lime peel have various anti-cancer effects on human liver cancer cells.
This compelling evidence provides incentives to grate citrus peel into salads, soups, stews, or baked goods. You can also use it to season rice, chicken or fish dishes, or grilled or roasted vegetables. Lime zest is used in some Thai soups and stews, and “in Mediterranean cuisine, there’s a longstanding tradition to candy citrus peels that you can have at the end of a meal,” Ayoob says.
Eggplant
The fact that the skin is dark purple should be a tip-off that it’s loaded with health-promoting antioxidants. In particular, eggplant skin contains nasunin, which protects cell membranes in the body and brain. Also, “nasunin reduces inflammation in the body and LDL cholesterol,” Salge Blake notes. Eggplant skin also has fiber.
When making eggplant parmesan, ratatouille, moussaka, or another dish, simply keep the peel on the eggplant as you prepare for cooking. For a special treat, Newgent recommends tossing strips of eggplant peel with olive oil and seasonings then baking them into a plant-based “bacon.”
Kiwis
Many people don’t realize kiwi skin is edible and good for you.
“The skin of kiwis has twice as much fiber as the interior,” says Alexandra Kazaks, a nutrition science and health research consultant in the Institute of Food Technologists Nutrition Division. The fuzzy skin also contains more folate and vitamin E than the flesh does.
Some experts recommend washing a kiwi and eating it like a peach or slicing it with the skin on. “When you slice it, you’re going to be eating more of the meat of the kiwi than the skin,” Salge Blake says. You can toss those slices into a fruit or leafy green salad or put kiwi chunks in a blender to make a smoothie. If you’re really put off by the fuzz, you might fare better with yellow kiwis, which aren’t as rough, Ayoob says.
Keep in mind: “If you have a history of kidney stones, you shouldn’t eat kiwi skins because they’re high in oxalates,” warns Young, author of Finally Full, Finally Slim.
Mango
It wouldn’t occur to many people to eat the peel from a mango—but it should. Not only is the brightly colored peel edible but it’s rich in vitamin C, carotenoids, fiber, and other antioxidants, too. And it’s “a good source of pectin, a viscous soluble fiber that reduces cholesterol levels and slows gastric emptying so you feel full for longer,” Salge Blake says.
Laboratory research suggests that eating mango peel may reduce fat accumulation in people. And various bioactive compounds—including phenolic acid, mangiferin, and beta carotene—in mango peel are recognized for their antimicrobial, anti-diabetic, anti-inflammatory, and anti-cancer properties.
You can cut a mango into chunks and eat it with the skin. Or cook with it: “Since mango peel can be a bit bitter, I suggest tossing mango skin into a stir-fry along with some of the sweet mango flesh for taste balance,” says Newgent, author of The Plant-Based Diabetes Cookbook.
A note of caution: Some people are allergic to compounds in the peels and may experience reactions such as rash, itching in the mouth or throat, or swelling of the lips, face, and eyes, Kazaks warns. So proceed slowly when eating a mango peel to be sure it agrees with you.
Potato
Potato skins often aren’t thought of as a healthy food because they’re a staple on bar menus, usually “gooped up with all kinds of fat,” Ayoob says, adding that “it doesn’t have to be that way.”
Not only is the spud skin rich in vitamin C, iron, potassium, and some B vitamins, but “50 percent of a potato’s fiber resides in the skin,” Salge Blake says.
So forget about peeling white, red, purple, or sweet potatoes. Simply scrub the skin with a vegetable brush under running water then cook it and eat it with the rest of the potato. Or, you can scoop out the “guts” of the potato and eat the baked skins topped with sautéed onions and mushrooms (or other veggies) and a dollop of plain Greek yogurt. Newgent also suggests sautéing shredded peels with herbs or truffle salt and using them as a garnish on other dishes.
Tomato
Talk about a waste of time and nutrients: “Some people peel tomatoes when making a soup or a sauce but there’s no need to,” Salge Blake says. “By removing the skin, you can lose up to 80 percent of the lycopene, which helps fight cancer.”
The skin also has slightly higher concentrations of vitamin C and some B vitamins than the flesh. And research has shown that removing the skin decreases the overall antioxidant activity of tomatoes.
The solution: Use the entire tomato.. “Sometimes it makes cooking a lot easier if you don’t have to peel these things,” Ayoob says.