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

Abstract

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.Nutrients 2020, 12, 91 2 of 12 including prevention of metabolic syndrome for fresh vegetables, research on and development of various vegetables containing highly functional components is expected.Quercetin is a flavonoid that is abundant in vegetables such as onions and in fruit, tea, and wine [3][4][5]. It exhibits antioxidant [6,7] and antihypertensive effects [8,9]. In a placebo-controlled double-blind parallel-group comparison study for subjects with body mass index (BMI) of ≥25 kg/m 2 , daily intake of tea containing 110 mg quercetin glycoside for 12 weeks significantly decreased visceral fat area (VFA) at weeks 8 and 12 after intake compared to that in the placebo food intake group [10]. The mechanism underlying suppression of fat accumulation by quercetin was indicated to involve suppression of the expression of peroxisome proliferator-activated receptor γ which is related to fat accumulation, and sterol regulatory element-binding protein 1 and fatty acid synthase which are related to fatty acid synthesis, and to increase the expression of cAMP which is related to lipolysis [11][12][13].Onion is the one of the most popular vegetables in the world, and a major source of quercetin (28.4-48.6 mg/100 g) [14]. In the current clinical trial, we used the two quercetin-rich onion cultivars 'Quergold' and 'Sarasara-gold' to adjust the amount of quercetin contained in the test food. These onions were developed via selective breeding to develop onions containing increased amounts of quercetin. One 'Quergold' onion bulb (~140 g) contains 109 mg quercetin aglycone [15], and one 'Sarasara-gold' onion bulb (~200 g) contains 200 mg quercetin glycoside. The above findings suggest that the intake of 'Quergold' and 'Sarasara-gold' onion...

Comparative Metabolomics Profiling of Polyphenols, Nutrients and Antioxidant Activities of Two Red Onion (Allium cepa L.) Cultivars

“…[ 12 ]. Nishimura et al reported that the daily intake of onion rich in quercetin might improve liver function and have anti-obesity effects [ 13 ]. Due to the structural functionalities, quercetin has maximum radical scavenging activity and acts as a potent antioxidant, representing the main antioxidative flavonol in the human diet [ 14 ].…”

Effect of onion on blood lipid profile: A meta‐analysis of randomized controlled trials

“…Onions as a common food have been the subject of numerous clinical trials, only few side‐effects have been reported. Nishimura et al (Nishimura et al., 2019) reported four participants with mild gastrointestinal symptoms. In Song et al's study, two patients experienced transient itching after using the onion extract gel (Song et al., 2018).…”

Natural Polyphenols in Metabolic Syndrome: Protective Mechanisms and Clinical Applications

“…Oral administration with 150 mg/day quercetin for six weeks decreases systolic blood pressure (SBP) and plasma oxidized LDL (ox-LDL) concentrations [ 26 ], and in women with T2D, oral 500 mg/day quercetin significantly reduced the serum concentration of tumor necrosis factor α (TNF-α) and IL-6, as well as SBP [ 27 ]. Even at low doses of 60 mg/day, quercetin still reduced visceral fat and serum alanine transaminase (ALT) [ 28 ]. However, Verena Brüll et al reported a test of ineffective quercetin administration in overweight-to-obese patients with pre- and stage I hypertension [ 29 ], which may be related to the shorter treatment cycle and lower dosage.…”