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Onion extract

Also known as: Onion extract, Onion peel extract, Onion juice, Onion powder, Allium cepa

Overview

Onion extract is derived from the bulb of the common onion plant, Allium cepa, a widely consumed vegetable. It is recognized as a botanical supplement and functional food extract, primarily valued for its rich content of bioactive compounds, particularly quercetin and various sulfur compounds like thiosulfinates and sulfoxides. These components contribute to its potential health benefits, especially in the realm of cardiometabolic health. Available in forms such as extract, powder, or juice, onion extract is increasingly studied for its effects on weight management, lipid profiles, and blood pressure. While research is ongoing, several randomized controlled trials and meta-analyses suggest its efficacy in these areas, though the quality of evidence is often limited by modest sample sizes and heterogeneity in study designs and formulations. It is generally considered safe for consumption at typical doses.

Benefits

Onion extract has demonstrated several evidence-based benefits, particularly for individuals with obesity or dyslipidemia. A meta-analysis indicated that onion supplementation significantly reduced body weight by an average of 0.74 kg and improved body fat percentage. It also positively impacts lipid profiles, with studies showing an increase in HDL cholesterol by approximately 2.29 mg/dL, a reduction in LDL cholesterol by 6.64 mg/dL, and a decrease in total cholesterol by 5.39 mg/dL. Subgroup analyses suggest that prolonged supplementation (over 12 weeks) can lead to significant reductions in both systolic and diastolic blood pressure. Beyond these primary effects, onion extract exhibits secondary benefits including antioxidant activity, improved endothelial function, and modulation of obesity-related hormones like adiponectin and leptin. While the effect sizes are modest, they are statistically significant, suggesting clinical relevance, especially in at-risk populations. Most observed benefits typically manifest after at least 12 weeks of consistent supplementation.

How it works

Onion extract exerts its effects primarily through its rich content of quercetin and other polyphenols. Its mechanism of action involves significant antioxidant activity, which helps combat oxidative stress. It also plays a role in modulating lipid metabolism by inhibiting lipid absorption and influencing the body's fat storage processes. Quercetin, a key bioactive compound, is believed to act via the activation of AMPK (AMP-activated protein kinase) and modulation of PPAR-γ (peroxisome proliferator-activated receptor gamma), both of which are crucial in energy metabolism and adipogenesis. Furthermore, it exhibits anti-inflammatory effects and interacts with adipose tissue and vascular function, contributing to improved cardiometabolic health. Quercetin is absorbed in the small intestine, with its bioavailability being moderate and potentially enhanced when consumed with dietary fats.

Side effects

Onion extract is generally well tolerated at typical doses. The most common side effects, reported in over 5% of users, are mild gastrointestinal discomforts such as bloating and gas. Uncommon side effects, occurring in 1-5% of individuals, include rare reports of allergic reactions. Severe or rare side effects are not well documented but are considered extremely rare. Caution is advised regarding potential drug interactions, particularly with anticoagulants, due to the antiplatelet effects of quercetin, which could theoretically increase the risk of bleeding. Individuals with a known allergy to onions or related plants should avoid onion extract. Safety in special populations, such as pregnant or lactating women, has not been established, and its use in these groups, as well as in individuals with bleeding disorders, should be approached with caution.

Dosage

While a minimum effective dose is not definitively established, most studies on onion extract utilize dosages ranging from 100 to 900 mg per day. For onion peel extract, an optimal dosage range appears to be 100–468 mg per day, whereas steamed onion capsules have been studied at up to 900 mg per day. The maximum safe dose is not precisely defined, but doses up to 900 mg per day have been observed to be safe in clinical studies. To enhance absorption, it is generally recommended to take onion extract with meals, as its absorption can be improved by dietary fats. Onion peel extract is the most studied form and is often standardized to its quercetin content. No specific cofactors are identified as necessary for its efficacy.

FAQs

What are the main benefits of taking onion extract?

Onion extract has been shown to modestly improve body weight, body fat percentage, and lipid profiles by increasing 'good' HDL cholesterol and decreasing 'bad' LDL and total cholesterol. It may also help reduce blood pressure with prolonged use.

Are there any common side effects?

The most common side effects are mild gastrointestinal issues like bloating and gas. Allergic reactions are rare but possible, especially if you are sensitive to onions.

How should I take onion extract for best results?

It's generally recommended to take onion extract with meals, as dietary fats can enhance the absorption of its active compounds like quercetin. Benefits typically appear after 12 weeks of consistent use.

Can onion extract interact with medications?

Yes, due to its antiplatelet effects, onion extract may potentially interact with anticoagulant medications. If you are on blood thinners, consult your doctor before taking onion extract.

Is onion extract a substitute for diet and exercise?

No, onion extract is not a substitute for a healthy lifestyle. Its effects are modest and it should be used as a supplement to, not a replacement for, a balanced diet and regular exercise.

Research Sources

https://pmc.ncbi.nlm.nih.gov/articles/PMC10420769/ – This meta-analysis investigated the antiobesity effects of onion in subjects with obesity. It found significant reductions in body weight, BMI, and body fat, along with improvements in lipid profiles and obesity-related hormones after 12 weeks of supplementation. The study noted limitations due to few data points per outcome.
https://onlinelibrary.wiley.com/doi/10.1002/fsn3.2309 – This meta-analysis of 10 RCTs examined the effect of onion supplementation on lipid profiles. It concluded that onion significantly improved HDL, LDL, and total cholesterol, but had no significant effect on triglycerides. Limitations included small sample sizes and heterogeneity in formulations.
https://pubmed.ncbi.nlm.nih.gov/38056991/ – This systematic review and meta-analysis of 14 RCTs assessed onion supplementation for cardiometabolic health. It reported significant improvements in body fat, HDL, LDL, total cholesterol, and blood pressure, particularly with longer intervention durations. The study highlighted heterogeneity in interventions and populations as a limitation.