Admit it, the crisp, flaky outer scales of the onions you use in soups, salads, and casseroles usually end up in the trash (or perhaps more usefully, the compost bin).
But don’t toss them out before you’ve put them to use. For your health!
Recent research confirms that the outer skins of onions provide an exceptionally rich source of plant compounds called flavonoids, especially the powerful antioxidant and anti-inflammatory compound, quercetin .
Quercetin is under study as an agent for lowering LDL cholesterol and blood pressure, fighting allergies, reducing inflammation, enhancing muscle growth and function, treating depression, some forms of cancer, and other conditions.
“Plants are the master chemists," says Mary Ann Lila, who directs the Plants for Human Health Institute at North Carolina State University. "Because plants can't move around, they have to manufacture what they need, not merely to grow, but to defend, protect, and heal themselves. It makes sense that the compounds plants produce in response to stress would help a human under similar circumstances."
It also makes sense that plants would concentrate many of these protective compounds in the outer coverings--skins and peels of various roots and fruits--the point where most environmental assaults would likely occur.
To extract quercetin and other beneficial plant compounds that onions skins might contain, toss a whole onion or two, scales and all, into the pot next time you make soup, put a stew into the crock pot, or cook rice. Or, you could save the outer onion scales in a paper bag. Tie up a handful of onion skins loosely in the cut-off leg of an old pantyhose or a thin sock. You can discard the skins after the soup has simmered or the rice has cooked. Wash and save the “bag” for another use.
A nice side benefit: onion skins will impart a rich brown or deep mahogany color to your broth, depending on which color onion you use.
Other uses for onion skins
Noted ethnobotanist James Duke recommends an infusion of onion skins as a soothing wash for the itch of scabies and other skin disorders.
Although I haven’t tried it, onion skins make gorgeous dyestuffs for natural fibers. Take a peek .
Also, if you have a surplus, an onion-skin infusion has a long reputation as a softening and smoothing hair rinse. Just run the strained onion-skin broth through freshly washed hair a few times and let it air dry. (Yes, I have tried this, with positive results. Don’t worry. There’s no residual onion odor.)
A Japanese firm has developed a fermented onion-skin “health tea”  they claim concentrates the quercetin and removes the bitter aftertaste of the raw product. (The declared benefits might also derive from the fact that the tea contains nine other health-promoting herbs, including green tea and turmeric.)
Thanks, but I think I’ll stay with the soup stock.
Margaret Boyles lives in a wood-heated house in central New Hampshire. She grows vegetables, eats weeds, keeps chickens, swims in a backyard pond in summer, snowshoes in the surrounding woods in winter, and commutes by bike whenever possible.