Is raw red onion consumption effective in reducing cholesterol among overweight or obese women with polycystic ovary syndrome?
Date of publication of the randomized controlled trial: April 2014
Design
Randomized controlled trial (RCT).
Participants
54 women aged 17 to 37 years with polycystic ovary syndrome (PCOS), taking no medications at least 2 months before the enrollment, having no tendency to become pregnant during the study, and having a low intake (<93g) of liliaceous vegetables (mean age: 26.44 years for intervention group, 26.70 years for control group).
Intervention
Participants were instructed to receive their usual diet plus less liliaceous vegetables plus raw red onions. Two 40g to 50g raw red onions were consumed per day for overweight patients, while two 50g to 60g raw red onions were consumed per day for obese patients. One was consumed with lunch and another with dinner for 8 weeks.
Comparator
Comparison: High-onion consumption versus low-onion consumption. Low-onion consumption referred to two 10g to15g raw red onion per day.
Major Outcomes
Outcome 1: Levels of total cholesterol (TC) as measured after 8-week intervention;
Outcome 2: Levels of low density lipoprotein cholesterol (LDL-C) as measured after 8-week intervention.
Settings
This study was performed in an outpatient setting.
Comparison    High-onion consumption versus low-onion consumption
Main Results
Compared to low raw red onion consumption, high-onion did not significantly reduce levels of TC (weighted mean difference (WMD): -0.33, 95% CI: -5.14 to 4.48) and LDL-C (WMD: -1.14, 95% CI: -5.06 to 2.78) after 8-week treatment.
Comparison: High-onion versus low-onion consumption in overweight or obese women with polycystic ovary syndrome
Outcomes (unit) No. of studies (Total number of participants) Mean value (SD)/No. of participants Heterogeneity test ( I2) WMD (95% CI) Overall quality of evidence*
Intervention Comparator
1 (mg/dL) 1 (54) 181.40 (32.33)/27 183.44 (43.09)/27 Not applicable as there is only 1 study. -0.33 (-5.14 to 4.48) Moderate
2 (mg/dL) 1 (54) 109.22 (28.40)/27 111.69 (39.80)/27 Not applicable as there is only 1 study. -1.14 (-5.06 to 2.78) Moderate
Keys: WMD = weighted mean difference; CI = confidence interval.
Comparison    High-onion consumption versus low-onion consumption
Main Results
Compared to low raw red onion consumption, high-onion did not significantly reduce levels of TC (weighted mean difference (WMD): -0.33, 95% CI: -5.14 to 4.48) and LDL-C (WMD: -1.14, 95% CI: -5.06 to 2.78) after 8-week treatment.
Comparison: High-onion versus low-onion consumption in overweight or obese women with polycystic ovary syndrome
Outcomes (unit) 1 (mg/dL) 2 (mg/dL)
No. of studies (Total number of participants) 1 (54) 1 (54)
Mean value (SD)/No. of participants Intervention 181.40 (32.33)/27 109.22 (28.40)/27
Comparator 183.44 (43.09)/27 111.69 (39.80)/27
WMD (95% CI) -0.33 (-5.14 to 4.48) -1.14 (-5.06 to 2.78)
Overall quality of evidence* Moderate Moderate
Keys: WMD = weighted mean difference; CI = confidence interval.
Conclusion
Benefits
Compared to low raw red onion consumption, high raw red onion consumption reduced levels of TC and LDL-C among women with PCOS. However, the levels of TC and LDL-C reduction did not differ significantly between two groups after 8-week intervention. For all outcomes, the overall quality of evidence is moderate. Further research is fairly likely to have an important impact on our confidence in this estimate of effect.
Harms
The authors did not report details of adverse events.
Link to Original Article
https://www.ncbi.nlm.nih.gov/pubmed/24612081
The synopsis is based on the following article:
Ebrahimi-Mamaghani M, Saghafi-Asl M, Pirouzpanah S, Asghari-Jafarabadi M. Effects of raw red onion consumption on metabolic features in overweight or obese women with polycystic ovary syndrome: a randomized controlled clinical trial. J Obstet Gynaecol Res. 2014 Apr;40(4):1067-76.


* Interpretation of quality assessment results:
• Very low: Further research is most likely to have an important impact on our confidence in this estimate of effect.
• Low: Further research is likely to have an important impact on our confidence in this estimate of effect.
• Moderate: Further research is fairly likely to have an important impact on our confidence in this estimate of effect.
• High: Further research is unlikely to have an important impact on our confidence in this estimate of effect.
• Very high: Further research is most unlikely to have an important impact on our confidence in this estimate of effect.

Details of assessment method can be found at Chung VC, Wu XY, Ziea ET, Ng BF, Wong SY, Wu JC. Assessing internal validity of clinical evidence on effectiveness of CHinese and integrative medicine: Proposed framework for a CHinese and Integrative Medicine Evidence RAting System (CHIMERAS). European Journal of Integrative Medicine. 2015 Aug 31;7(4):332-41.