Effects of brown rice bran on appetite and depression in metabolic syndrome: a secondary analysis of an open-label randomised controlled trial

Although metabolic syndrome (MetSyn) patients are frequently reported to experience alterations in ghrelin levels, appetite regulation and mood, these issues have been largely overlooked. Thus, the present randomised controlled trial (RCT) examined the effects of incorporating brown rice bran powder (BRBP) into a standard diet on ghrelin levels, appetite control, depression, insulin resistance and atherogenicity indices. This secondary analysis used data from our 8-week RCT involving forty-three MetSyn patients, with nineteen on a standard diet and twenty-four receiving an additional 15 g/d of BRBP. Serum ghrelin levels were measured using an ELISA kit, and seven atherosclerosis-related indicators were assessed before and after the intervention. Appetite rating and depression status were evaluated using a four-component visual analogue scale (VAS) and the Beck Depression Inventory (BDI) questionnaires. The ANCOVA model adjusted for baseline values (and BMI for ghrelin) indicated that patients receiving BRBP plus the standard diet experienced significant increases in ghrelin levels and feelings of satiety and fullness compared with those on the standard diet alone (<i>P</i>-value < 0·008; effect sizes (ES) of 0·95, 1·14, and 1·34, respectively). BRBP intake led to significant reductions in atherogenic coefficient, Castelli risk index-II, cholesterol index, metabolic score for insulin resistance, BDI scores, and hunger sensations (<i>P</i>-value ≤ 0·05; ES of -0·94, -0·96, -0·81, -1·74, -0·98 and -0·71, respectively) compared with the standard diet alone. Overall, this secondary analysis of the RCT supports the efficacy of BRBP administration in enhancing ghrelin levels while reducing appetite-related indices, depression scores, as well as markers of atherogenicity and insulin resistance. Nevertheless, given the study's limitations, namely small sample size and lack of a placebo, further research is needed.