It’s common for home cooks to remove and throw away the outer onion peel before they add the vegetable to a dish—but doing so could mean missing out on a host of health benefits.
If you enjoy the taste, onion skins can be a great source of a number of anti-inflammatory nutrients, Erin Palinski-Wade, RD, CPT, a New Jersey-based dietitian and author, told Health.
“The outer skins of onions are nutritional powerhouses compared to the inner layers,” she said.
The outer layers of an onion are rich in antioxidants. Red onion skins, in particular, are a good source of a flavonoid called anthocyanin, while other peels are a good source of a flavonoid called quercetin.
Both anthocyanin and quercetin can help get rid of disease-causing free radicals in the body.
Flavonoids can be found in the rest of the onion, but at lower concentrations. In fact, a powder made of onion skin can contain over a dozen times more quercetin than the inner layers.
Onion skins have more dietary fiber than the inner part of an onion.
Though the large majority of Americans fall short on their recommended fiber intake, studies have linked a high-fiber diet to better bowel movements, more stable blood sugar, lower cholesterol, cancer prevention, greater satiety, and more.
A major bonus of adding onion skins to your diet is that they can help you reduce food waste, Megan Meyer, PhD, a nutritional immunology researcher based in North Carolina, told Health.
“In some countries, it is estimated that 300–500 kilograms of onion skin is wasted every day. In the U.S., about 30–40% of the food supply is wasted,” she said. “I love finding new ways to use up all parts of a food.”
Some companies are embracing this mentality by adding onion skins to processed food, which both reduces waste and boosts nutritional value.
“Specifically, a study using onion skin as an ingredient in fortified pasta found that it improved the nutritional properties of the pasta,” Meyer said. “Because of this, onion skins have been incorporated into foods like gluten-free bread, wheat bread, and meat patties.”
Onion skins can be safe to use in small amounts. However, eating them raw isn’t recommended. That’s because they’re hard to chew, and may pose a choking risk, Palinski-Wade said.
They’re also difficult to digest, she explained, “particularly for those with sensitive stomachs or irritable bowel syndrome.”
Another potential risk? Pesticide residue, Palinski-Wade said. For that reason, she recommends choosing organic onions or washing the skins very thoroughly.
Onions have also been involved in a number of food recalls recently, and the outer layers have a higher likelihood of being contaminated with bacteria. While there isn’t much you can do, Meyer said it’s important to practice safe food handling, which follows four steps: clean, separate, cook, and chill.
One of the easiest ways to cook with onion peels involves adding them to a big batch of vegetable or chicken stock, Meyer suggested.
“You could also simmer onion skins in soups or stews to increase the depth of flavor,” she said.
Just remember to strain out the skins before serving.
“Another fun option is to dry and grind the clean skins into a fine powder to use as a seasoning, or even mix into baked goods like biscuits for flavor with a nutrient boost,” Palinski-Wade added.
