Onion supplements and metabolic health markers across 14 trials in people
What it found
Taking onion supplements improved body fat, cholesterol, blood pressure and a liver enzyme in people.
Longer use or higher doses brought more benefits.
What they found
Studies in people
Body fat and cholesterol
Onion supplements lowered body fat percentage, LDL cholesterol and total cholesterol. They also raised HDL cholesterol in people.
Blood pressure
Systolic blood pressure dropped with onion supplements in people. Diastolic blood pressure also fell when the intervention lasted over 12 weeks.
Liver enzymes
A liver enzyme called AST improved with onion supplements in people. Another liver enzyme, ALT, improved at doses above 300 mg per day.
Hormones adiponectin and leptin
The hormone adiponectin improved with onion supplements in people. The text does not report clear changes for leptin.
Longer duration effects
Trials lasting more than 12 weeks showed improvements in weight, waist size and body mass index in people. These longer trials also improved body fat, cholesterol and both blood pressure readings.
Higher dose effects
Doses above 300 mg per day improved weight, waist size and body mass index in people. These higher doses also improved body fat, all measured cholesterol types, liver enzymes and blood pressure.
What the authors conclude
- They suggest that taking onion supplements can improve various metabolic health markers in people.
- They note that longer study periods or higher supplement doses lead to greater improvements in heart and metabolic measures.
How it was done
Onions are considered functional foods and have been studied often. The authors wanted to gather existing trial data on how onion supplements affect body measurements, blood fats, blood sugar control, liver health, blood pressure and certain hormones.
They searched major online databases for randomised controlled trials up to October 2022. They found 14 eligible trials testing onion supplements in people. They combined the results to calculate overall differences.
What it can’t tell you
- We summarised it from the abstract only.
- These trials tested concentrated onion supplements rather than onions eaten as food. The results may not apply to eating regular onions in meals.
- Combining many trials shows an overall pattern but individual studies may have varied in quality or design.
Who paid
- Conflicts
- Declaration of competing interest The authors declared no conflicts of interest.
- Authors work at
- Shiraz University of Medical Sciences, Iran
The paper
- Title
- Onion supplementation and health metabolic parameters: A systematic review and meta-analysis of randomized controlled trials
- Type
- Systematic review and meta-analysisThe authors follow a set, published method to find every relevant study, then combine the numbers from them into one result.
- Evidence
- Studies in people
- Summarised from
- Abstract only
- Cite
- Hejazi N, Ghalandari H, Nouri M, Askarpour M (2023). Onion supplementation and health metabolic parameters: A systematic review and meta-analysis of randomized controlled trials. Clinical nutrition ESPEN. doi:10.1016/j.clnesp.2023.08.032PubMed 38056991DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error