Onion

Studies in people

• Open question

  Heart and body measures²

  People taking onion supplements saw changes in cholesterol, blood pressure, body fat, weight, and liver markers.

• Benefit

  General health benefits³

  Green onions add flavor and nutrients to meals, and eating them may help prevent some diseases.

• Benefit

  Cholesterol levels⁴

  In people with mildly high cholesterol, a garlic and onion extract capsule lowered LDL and total cholesterol.

• Benefit

  Breast cancer risk⁷

  Women who ate more onion and garlic were less likely to get breast cancer, but this study alone cannot prove cause.

• Benefit

  Blood fats after a fatty meal⁸

  In people, onion and garlic juice or their oils seemed to protect against blood fat rises after eating butter.

• Benefit

  Blood sugar after meals⁹

  In people, an onion meal cut peak blood sugar more in lactose-intolerant adults than in lactose-tolerant ones.

• Benefit

  Prostate enlargement risk¹⁰

  Men who ate more onion and garlic were less likely to have an enlarged prostate.

• Benefit

  Cancer risk in people¹¹

  People who ate more onion and garlic seemed less likely to get several common cancers, though this link is not proof.

Animal and lab studies only

• Benefit

  Lab study health effects¹³

  In lab studies, onion extracts and compounds showed antimicrobial, antidiabetic, anti-inflammatory, anticancer and other activities.

• Benefit

  Male hormone levels¹⁴

  Onion may raise testosterone in men, but most studies were in rats and more human research is needed.

• Benefit

  Gut bacteria balance¹⁵

  In lab studies, onion extracts changed gut bacteria and boosted helpful compounds, but it is not known if this happens in people.

• Benefit

  Kidney damage in diabetes¹⁶

  In diabetic rats, eating onion with fenugreek seeds reduced kidney stress and damage.

• Benefit

  Colon cancer cells¹⁷

  In lab studies, a compound formed when onion cooks with beef slowed colon cancer cell growth.

Study type not stated

• Open question

  Overall health effects¹²

  Compounds in onion have been reported to affect cancer, blood clotting, asthma, and bacterial infections.

Found in some samples or products

These come from where it was grown, how it was processed or cooked, or what it was made into. They are not about the ingredient itself, so the signal does not count them.

• Asthma attacks from food⁶

  Some young people with asthma had attacks right after eating pickled onions, which can hold high levels of sulfites.

Allergies and intolerances

These are about people with an allergy, an intolerance or coeliac disease. The signal is about the ingredient itself, and these are about the person eating it, so the signal does not count them.

• Food allergy symptoms⁵

  In people, onion caused allergy symptoms in a small number of those tested, linked to a specific protein.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.