Effect of Daily Ingestion of Quercetin-Rich Onion Powder for 12 Weeks on Visceral Fat: A Randomised, Double-Blind, Placebo-Controlled, Parallel-Group Study

Nutrients. 2019 Dec 28;12(1):91. doi: 10.3390/nu12010091.


Quercetin, which is frequently found in vegetables such as onion, is widely found to have biological activities such as visceral fat reduction. Therefore, we performed this randomised double-blind placebo-controlled parallel-group study and analysed the effects of daily intake of quercetin-rich onion on visceral fat for 12 weeks. Seventy healthy Japanese subjects whose body mass index (BMI) was ≥23 and <30 were recruited and randomly assigned to either the quercetin-rich onion group or placebo group. The subjects ingested 9 g of onion powder per day for 12 weeks. We conducted medical interviews, hematological and biological tests; measured body composition and vital signs; and analysed the Food Frequency Questionnaire weeks 0, 4, 8, and 12. Abdominal fat area was measured using computed tomography scanning at weeks 0 and 12. No significant differences in visceral fat area (VFA) were observed between the two groups. However, in subjects whose high-density lipoprotein cholesterol was lower, VFA was significantly lower in the quercetin-rich onion group. In addition, alanine aminotransferase was significantly lower in the quercetin-rich onion group than in the placebo group. Thus, the results suggest that quercetin-rich onion may be beneficial for preventing obesity and improving liver function.

Keywords: alanine aminotransferase; onion; quercetin; randomised controlled trial; visceral fat.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Alanine Transaminase / blood
  • Body Composition / drug effects
  • Cholesterol, HDL / blood
  • Double-Blind Method
  • Eating
  • Female
  • Humans
  • Intra-Abdominal Fat / drug effects*
  • Japan
  • Male
  • Middle Aged
  • Nutrition Surveys
  • Obesity / drug therapy*
  • Onions / chemistry*
  • Phytotherapy*
  • Plant Extracts / administration & dosage
  • Quercetin / administration & dosage*
  • Time Factors


  • Cholesterol, HDL
  • Plant Extracts
  • Quercetin
  • Alanine Transaminase