A 12-week randomized controlled trial in 39 overweight adults with prediabetes (HbA1c 5.7–6.4%, BMI 25–29.9 kg/m²) found that daily supplementation with whole-fruit feijoa powder (Feiolix) significantly reduced HbA1c by 0.5% (high-dose, 1,150 mg/day) and 0.4% (low-dose, 300 mg/day) versus placebo. Both doses also significantly lowered fasting glucose, fasting insulin, HOMA-IR, total cholesterol, and LDL cholesterol. The high dose additionally attenuated triglyceride increases and reduced body weight and BMI by month two. No GLP-1 changes were detected, and no adverse events were reported. The proposed active constituents — abscisic acid, polyphenols, and dietary fibre — suggest multi-pathway metabolic support.
A 0.5% HbA1c reduction in prediabetes is clinically meaningful: population studies show each 0.1% reduction at this stage meaningfully lowers T2D progression risk. Feijoa remains understudied compared to better-characterized polyphenol sources like berberine or green tea extract, so this trial adds genuinely novel data. However, critical limitations temper enthusiasm: the sample of just 39 participants is far too small for robust conclusions, the 12-week window cannot reveal long-term durability, and the industry-adjacent framing warrants scrutiny of potential conflicts of interest. The unexplained absence of GLP-1 response despite glycemic improvement also invites mechanistic questions. As an unreviewed preprint posted on medRxiv, these findings have not yet undergone peer review and should be treated as preliminary — confirmatory trials with larger, more diverse cohorts are essential before any clinical recommendations.