'Unexpected' source of nutrients from the peels of many vegetables and fruits

According to National Geographic, studies show that the peels of certain fruits and vegetables contain antibacterial compounds and chemicals that fight diabetes , inflammation, and cancer.

Here are some of the most nutritious:

Apple

When it comes to apples, "the skin is the most nutritious part," says Joan Salge Blake, professor of nutrition at Boston University. " The skin 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. "You'll chew more if you eat the skin, which slows down your eating."

So don't bother peeling your apples, whether you're eating them raw, cooked, or baked. For a delicious snack or dessert, roast whole apples in the oven or peel and bake strips with a dash of cinnamon.

The peels of some fruits and vegetables contain many antibacterial compounds. (Illustration: National Geographic).

Carrot

Research has shown that the skin of a fresh carrot makes up only 11% of its weight but contains 54% of its phenolic acids – which act as antioxidants. Carotenoids, vitamin K, niacin and vitamin C are also more concentrated in the skin than in the inside of the carrot.

Just wash carrots and eat them raw or cooked. You can peel them into strips and fry them for a light crunch; or use peeled "carrot strips" in salads, says Jackie Newgent, a New York-based nutritionist and vegetable chef.

Citrus fruits

The peels of oranges, grapefruits, and lemons not only contain more vitamin C and carotenoids than the pulp, but are also rich in hesperidin - a powerful antioxidant that has anti-inflammatory properties and may help regulate blood sugar levels.

Research has found that people in Arizona who regularly eat citrus peels have a 34% lower risk of developing squamous cell carcinoma of the skin. Another study found that citrus peels may have neuroprotective effects, improving cognitive function in older adults.

And a 2023 study in the journal Molecules found that substances in lemon peel have various anti-cancer effects on liver cancer cells.

You can zest citrus into salads, soups, stews or baked goods; or season rice, chicken or fish dishes, or grilled or sauteed vegetables.

Eggplant

The deep purple skin indicates that eggplants are loaded with health-promoting antioxidants. In particular, eggplant skin contains nasunin, a substance that protects cell membranes in the body and brain. Additionally, Salge Blake notes that "nasunin reduces inflammation in the body and LDL cholesterol."

When making eggplant dishes, just save the skins until you're ready to cook them. For a special treat, Newgent suggests tossing strips of eggplant skin with olive oil and spices and baking them to create a faux "bacon" dish.

Kiwi

Many people do not know that kiwi skin is edible and good for health.

'The kiwi skin has twice the amount of fibre as the inside,' says Alexandra Kazaks, a research advisor in health and nutrition science at the Institute of Food Technologists. The fuzzy skin also contains more folate and vitamin E than the 'flesh'.

Some experts recommend washing kiwis and eating them like peaches or slicing them with the skin on. "When you slice them, you're eating more of the 'meat' of the kiwi than the skin," says Salge Blake . You can mix the slices into a fruit or vegetable salad or toss them into a blender to make a smoothie.

Remember: "If you have a history of kidney stones, you should avoid kiwi skins because they are high in oxalates," warns Young, author of 'Finally Full, Finally Slim' .

Mango

People wouldn't normally think of eating the mango skin - but you should.

The brightly colored skin of mangoes is not only edible, but also rich in vitamin C, carotenoids, fiber, and other antioxidants. And it's "a good source of pectin—a viscous soluble fiber that helps lower cholesterol levels and slows stomach emptying, helping you feel fuller longer," says Salge Blake.

Research shows that eating mango peel can reduce fat accumulation in humans. And various bioactive compounds – including phenolic acids, mangiferin and beta carotene – in mango peel are recognized for their antibacterial, anti-diabetic, anti-inflammatory and anti-cancer properties.

 Research shows that eating mango peel can reduce fat accumulation. (Photo: Internet).

You can cut the mango into pieces and eat the skin, or use it for cooking.

"Since mango peel can be a little bitter, I recommend sautéing it with some of the sweet mango flesh to balance the flavor," says Newgent, author of 'The Plant-Based Diabetes Cookbook.'

Potato

Potato skins are often overlooked as a health food because they're a staple of bar menus, often "slathered with all sorts of fat," says Keith Ayoob, a dietitian at Albert Einstein College of Medicine in The Bronx. "But that's not necessarily the case."

Potato skins are not only rich in vitamin C, iron, potassium, and several B vitamins, but "50 percent of a potato's fiber is in the skin," says Salge Blake. So forget about peeling potatoes or sweet potatoes: Just scrub the skin under running water, then cook and eat with the rest of the 'meat.'

Or you can scoop out the potato 'inside' and eat the skins baked with sauteed onions and mushrooms (or other vegetables). Newgent also suggests sautéing chopped potato skins with herbs as a 'garnish' for other dishes.

Tomato

Talk about wasted time and nutrients: 'Some people peel tomatoes when making soups or sauces, but there's no need to do that,' says Salge Blake. 'Removing the skin means you can lose up to 80% of the cancer-fighting lycopene.'

The skin also has slightly higher concentrations of vitamin C and some B vitamins than the 'flesh.' Research has shown that removing the skin reduces the overall antioxidant activity of tomatoes.

The solution is to use whole tomatoes. 'Sometimes it's a lot easier to cook if you don't have to peel these,' says Ayoob.