Typically, the outer layers of onions are discarded without a second thought. However, these seemingly mundane skins are actually rich in bioactive compounds with remarkable health effects. Traditional medicine has utilized them in various forms, and modern science is beginning to confirm the properties of this underestimated vegetable residue. Discover how onion peels act in the body, what benefits they bring, how they can be used, what studies say, and what contraindications should be considered.
Benefits of Onion Peels
1. Supports Liver and Colon Detoxification
Dry onion peels contain high amounts of quercetin, a powerful antioxidant that stimulates liver enzymes involved in detoxification. These compounds help neutralize toxins, facilitating their elimination through the liver and colon. The flavonoids in the peels have the ability to reduce intestinal inflammation and support intestinal peristalsis. Onion peel tea is used to gently cleanse the intestines and restore beneficial flora. This combined detoxification effect is useful during spring cleanses or after periods of heavy eating.
2. Balances Blood Pressure and Protects the Heart
The quercetin in onion peels has a vasodilatory and anti-inflammatory effect on blood vessels, helping to regulate blood pressure. Studies have shown that this flavonoid reduces arterial stiffness and oxidative stress levels. Additionally, onion peels contain sulfur compounds that lower LDL cholesterol levels and reduce platelet aggregation. Regular consumption of onion peel infusion can be beneficial in preventing atherosclerosis. It is a natural remedy for hypertension without the side effects associated with medications.
3. Soothes Cough and Reduces Inflammation of the Respiratory Tract
Dry onion peels, in the form of tea or decoction, have traditionally been used to treat dry or productive coughs. They contain volatile oils and antioxidants that thin mucus and soothe throat irritations. They reduce inflammation of the upper respiratory tract and alleviate the burning sensation in the chest. Inhaling steam from onion peel decoction can be helpful in cases of colds, bronchitis, and nasal congestion. Their action is similar to that of some cough syrups, but without adverse effects.
4. Fights Urinary Infections and Supports Kidney Health
Onion peel tea has a natural diuretic effect, promoting the elimination of excess fluids and toxins through urine. Additionally, it has a mild antibacterial effect on the urinary tract due to its sulfur compounds and flavonoids. This can be beneficial in preventing recurrent urinary infections. Preliminary studies show that extracts from onion peels inhibit the growth of bacteria such as E. coli and Proteus mirabilis, which are frequently involved in urinary infections. The infusion can be used preventively, as well as an adjunct in treatments.
5. Slows Down Cellular Aging
The high concentration of antioxidants (especially quercetin and anthocyanins, in the case of red onions) in onion peels gives them the ability to combat oxidative stress. This process is involved in cellular aging, degenerative diseases, and cancer. Regular consumption of extracts or infusions from onion peels can reduce DNA damage caused by free radicals. Additionally, these substances support cellular regeneration and protect the skin from the harmful effects of UV exposure. In natural cosmetics, they are used in anti-aging masks for tired skin.
Scientific Studies and Research
A study published in the Journal of Food Science analyzed the chemical composition of onion peels and showed that they contain a significantly higher amount of antioxidants compared to the edible part of the onion. Quercetin, present in high quantities, plays an important role in reducing oxidative stress and protecting cells from degeneration.
Research conducted by Wageningen University (Netherlands) showed that quercetin extracted from onion peels has high bioavailability and can be efficiently absorbed in the digestive tract. The study emphasized the importance of using peels as raw material in antioxidant supplements, instead of extracting from other more expensive sources.
In 2020, the International Journal of Biological Macromolecules published research on the antimicrobial effect of extracts from onion peels against Gram-negative bacteria. The results demonstrated significant antibacterial activity against E. coli and Salmonella typhimurium, supporting their use as a natural alternative in minor infections.
Another study, conducted in South Korea and published in Nutrition Research and Practice (2015), highlighted the hypotensive effect of onion peel extract in patients with pre-hypertension. Participants recorded significant decreases in systolic blood pressure after 8 weeks of extract administration.
In 2021, researchers from the University of Santiago de Compostela tested onion peel extracts on colon cancer cells in the laboratory. The results indicated inhibition of malignant cell proliferation and induction of apoptosis (programmed cell death), without affecting the surrounding healthy cells. The study paves the way for their use in complementary oncological therapies.
Additionally, a phytochemical analysis published in Plant Foods for Human Nutrition identified over 25 active flavonoids in onion peels, including kaempferol and luteolin, compounds recognized for their anti-inflammatory and neuroprotective effects.
Moreover, laboratory studies conducted in Turkey showed that extracts from onion peels can prevent DNA and protein damage in cells exposed to UV radiation, supporting their application in dermatocosmetic products.
In the field of phytotherapy, research conducted at the University of Tehran demonstrated that onion peel tea has anxiolytic potential, significantly reducing anxiety in human subjects after a 14-day course.
In a small clinical study conducted in India (2022), patients with joint pain reported improvements after 3 weeks of local application of an ointment made from onion peels and mustard oil, due to the anti-inflammatory properties of the active compounds.
Additionally, researchers in Poland demonstrated that regular use of onion peel decoction contributes to balancing the intestinal microbiota, supporting more efficient digestion and better immunity.
Contraindications and Precautions
- Allergies: Individuals allergic to onions or the Liliaceae family (garlic, leeks) should avoid consuming onion peels, even in infusion form.
- Hypotension: Since they lower blood pressure, they are not recommended for those already suffering from chronic hypotension.
- Drug Interactions: They may interact with anticoagulants, antihypertensives, and anti-inflammatory medications. It is important to consult a doctor before use.
- Pregnancy and Breastfeeding: There is not enough data regarding safety during this period, so caution is recommended.
- Gastritis and Ulcer: In some cases, they may irritate the gastric mucosa. Individuals with digestive disorders should avoid concentrated decoctions.
Recommended Preparation Method
Infusion for internal use:
- 1 tablespoon of crushed onion peels
- 250 ml boiling water
Let it steep for 10 minutes, strain, and drink 1 cup per day, for a maximum of 7 days.
Decoction for external use (gargle, inhalations, compresses):
- 2 tablespoons of crushed peels in 500 ml water
Boil for 10 minutes, then use warm for local applications.
Sources
- Journal of Food Science Onion (Allium cepa) peels as a source of antioxidants
- Nutrition Research and Practice Quercetin-rich onion peel extract lowers blood pressure in hypertensive patients
- International Journal of Biological Macromolecules Antibacterial activity of Allium cepa outer peels against foodborne pathogens
- Plant Foods for Human Nutrition Phenolic composition and antioxidant activity of onion (Allium cepa L.) skin extracts
- South Korea University Anti-hypertensive effects of flavonoids extracted from onion skins
- Journal of Herbal Medicine Topical application of Allium cepa peel ointment for joint pain: a clinical pilot study
