Effects of raw red onion consumption on metabolic features in overweight or obese women with polycystic ovary syndrome: A randomized controlled clinical trial

Aim: We aimed to evaluate the effects of raw red onion consumption on metabolic features in overweight and obese women with polycystic ovary syndrome. Material and Methods: In this randomized controlled clinical trial, the patients (n = 54) were randomly allocated to the intervention group as 'high-onion' (raw red onions: 2×40-50 g/day if overweight and 2×50-60 g/day if obese) or to the control group as 'low-onion' (raw red onions: 2×10-15 g/day) along with limited liliaceous vegetables for 8 weeks. Body mass index, dietary record, and metabolic parameters (fasting blood sugar, triglycerides, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and lipoprotein (a)) were evaluated in the follicular phase of the menstrual cycle at baseline and after 8 weeks. Hormonal variables (progesterone, prolactin, and 17-OH progesterone) were also measured at baseline. Results: Onion significantly decreased the levels of total cholesterol within each group; however, these changes were stronger in the high-onion group (weighted mean differences [WMD]: -5.60 [95% confidence interval [CI]: -9.16, -2.03]; P = 0.003) than in the low-onion group (WMD: -6.42 [95%CI: -11.97, -0.87]; P = 0.025). Similarly, low-density lipoprotein cholesterol decreased significantly (WMD: -5.13 [95%CI: -9.46, -0.81); P = 0.022) in the high-onion group, and (WMD: -2.90 [95%CI -5.57, -0.21]; P = 0.035) in the low-onion group after treatment. The levels of fasting blood sugar, triglycerides, high-density lipoprotein cholesterol and lipoprotein (a) did not differ significantly after 8-week onion treatment. Adjustment for confounders did not make any significant changes in any of the parameters in post-treatment levels. Conclusion: Raw red onion consumption appears to be effective as a cholesterol-lowering food agent in women with polycystic ovary syndrome. However, further investigation is warranted.