Health Notes


Also indexed as:Allium cepa
Onion: Main Image © Martin Wall
Botanical names:
Allium cepa


Like its close cousins garlic, chives, scallions, and leeks, onion is a member of the lily family (Liliaceae). It is native to Eurasia but now grows all over the world, due mostly to people bringing it with them as a staple food wherever they migrated. The French explorer Pere Marquette was saved from starvation in 1624 by eating wild onions near the present site of Chicago—the name of the city is derived from a Native American word for the odour of onions.1 The bulb of the plant is used medicinally.

  • Reliable and relatively consistent scientific data showing a substantial health benefit.
  • Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
  • For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

Our proprietary “Star-Rating” system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by the medical community, and whether studies have found them to be effective for other people.

For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.

This supplement has been used in connection with the following health conditions:

Clinically relevant conditions Dosage Indications
Type 2 Diabetes
2 to 3.5 ounces fresh onion daily 2 stars [2 stars]
Onion may lower blood glucose levels and improve glucose tolerance in people with type 2 diabetes.
Refer to label instructions 1 star [1 star]
Onion may act as an anti-inflammatory in people with asthma.
Refer to label instructions 1 star [1 star]
Onion has a long history of use for relieving coughs.
Refer to label instructions 1 star [1 star]
Onion injections into the skin and topical onion applications have been shown to inhibit skin inflammation in people with eczema, according to one trial.
Refer to label instructions 1 star [1 star]
Onion is a herb that directly attack microbes.
Type 1 Diabetes
Refer to label instructions 1 star [1 star]
Research in laboratory animals suggests onion and its active constituents may lower blood glucose levels, raise insulin levels, reduce advanced glycation end-product (AGE) formation, and possibly prevent diabetes complications.

Historical or Traditional Use

Onion has been used as food for many centuries.2 Onion was also a popular folk remedy, being applied to tumours, made into a syrup for relieving coughs, or prepared in a tincture (using gin) to relieve “dropsy” (heart failure–related oedema).3 It was considered a weaker version of garlic by many herbal practitioners. Like garlic, onion has a longstanding but unsubstantiated reputation as an aphrodisiac.4

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The information presented by TraceGains is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2024.