Most people are familiar with reaching for their vegetable scraper or paring knives to prepare fresh produce before they’re ready to eat. It turns out that the peels our grandmothers and moms taught us to use are delicious and healthy. These six foods are easy to forget about — and six that you should still peel.

You shouldn’t peel fruits and vegetables

1. Potatoes

You may need to peel potatoes in order to make them more palatable for stews and mashed potatoes. However, it is a good idea to leave the skin on potatoes. Both sweet potato and potato skins are rich in fiber and iron, as well as potassium. Before you begin cooking, rinse the skins and scrub them with a kitchen towel.

2. Carrots

You only need to use running water and a quick scrub when cleaning these orange root vegetables. The majority of vitamin C and vitamin D found in carrots are actually found in the skin and the very thin layer below it (called the “phloem”), so leave the skin on to get the most of these vitamins. You should peel them if you plan to roast them. The skin can become a bit bitter if it isn’t.

3. Eggplant

Eggplant can be eaten cooked, but it is not recommended to be eaten raw. There’s no need to peel it. Because of the vegetable’s high water content, most of its nutrients like fiber, manganese and immune-boosting antioxidants are found in the skin. To clean the eggplant, rinse it and wipe it with a towel.

4. Cucumbers

Cucumbers are high in water, so you will find the majority of the good stuff in your skin. Vitamin K (good for bones health) and Vitamin A (good for your eyes and skin). You may find some cucumbers with tough outer layers. If you don’t want to peel them, rinse and scrub them well before eating.

5. Kiwi

While you may eat the fuzzy skin from a peach, did you know that you can also eat the fuzzy skin from a kiwi? The fiber in kiwi skin can be tripled. It will taste the same as the flesh but it will be a bit sweeter and tarter.

6. Zucchini

Zucchini, like its yellow cousin, summer squash, has many good-for you perks, including high levels of antioxidants as well as soluble and insoluble fibre. This is due to the high water content. To clean zucchini and summer squash, a quick rinse with water and a gentle rub with a towel is enough.

Vegetables and Fruits You Should Peel

1. Avocados

You can throw away the skin if you plan to eat this creamy fruit uncooked. The Hass avocado peel, which is the most common variety in American grocery stores and restaurants, is tough, thick, and doesn’t taste good. It is technically edible, however. You can use avocado in smoothies, but you should also consider using a different variety with a thinner skin.

2. Citrus Fruits

Many recipes require the grated zest of lime, orange, or lemon. Save the skin when you juicing citrus fruits or as a snack.

3. Pineapples

To protect their delicate insides from harsh climates, tropical fruits such as pineapple have tough skins. It is not a good idea to eat their skin.

4. Mangoes

Mango skins can be eaten, although they do contain some urushiol which is the active chemical in poisoned ivy. To be safe, you should toss the mango skin, especially if it contains urushiol, which is active in poison ivy.

5. Butternut Squash

Butternut squash skin can be difficult to peel and is a barrier between us and the delicious flesh. It is important to always peel it. The same applies for red kuri and kabocha squash. The peels of honeynut, delicata and acorn squash will soften in the oven so leave them on.

6. Bananas

Banana peels are a topic of contention for many people. These peels are technically safe to eat but they don’t taste good and have a bad texture. They do contain nutrients so you can mix, fry, or bake them.