Remission of impaired glucose tolerance by anthocyanin supplementation: a randomized, double-blind, and placebo-controlled trial.

Anthocyanin supplementation did not significantly improve the primary outcome of β-cell function as measured by disposition index (DI).

• The adjusted mean difference in DI between anthocyanin and placebo groups was 61.3 (95% CI: -27.4, 150.0; P = 0.174).
• The trial used 160 mg/d anthocyanin or placebo for 12 weeks.
• 68 IGT participants were enrolled and analyses followed the intention-to-treat principle.
• The trial was a randomized, double-blind, placebo-controlled design with routine lifestyle guidance.

The IGT reversion rate was significantly higher in the anthocyanin group compared to the placebo group.

• IGT reversion was defined as 2-hour OGTT glucose <7.8 mmol/L.
• The anthocyanin group had a reversion rate of 55.9% compared with 29.4% in the placebo group (P = 0.013).
• This represents a clinically meaningful difference in normalization of glucose tolerance.

Anthocyanin supplementation significantly improved insulin sensitivity as measured by the Matsuda index.

• The adjusted difference in Matsuda index between groups was 4.6 (95% CI: 2.5, 6.7; P = 0.003).
• The Matsuda index is an OGTT-derived measure of whole-body insulin sensitivity.
• This improvement in insulin sensitivity was identified as the primary mechanism by which anthocyanins reversed IGT.

Skin advanced glycation end products (AGEs) decreased significantly only in the anthocyanin group.

• Skin AGEs were measured by skin autofluorescence.
• No significant reduction in skin AGEs was observed in the placebo group.
• The reduction in skin AGEs was positively correlated with the decrease in postprandial glucose AUC (r = 0.302, P = 0.001).
• The reduction in skin AGEs was negatively correlated with improved Matsuda index (r = -0.344, P < 0.001).

The study enrolled individuals with impaired glucose tolerance (IGT) in a 12-week randomized controlled trial with two parallel arms.

• 68 IGT participants were randomized to anthocyanin 160 mg/d or placebo.
• The trial included routine lifestyle guidance for both groups.
• Secondary outcomes included OGTT-derived indices, insulin sensitivity, anthropometric measures, and skin AGEs.
• The trial was registered at chictr.org.cn as ChiCTR2400079566.

Anthocyanin supplementation is proposed as a promising nutritional intervention for prediabetes, with efficacy varying due to disease heterogeneity.

• Prior evidence showed heterogeneous efficacy of anthocyanin supplementation across prediabetes subtypes.
• This trial specifically targeted the IGT subtype of prediabetes.
• The authors suggest that reduction of skin AGEs by anthocyanins might play a critical role in the dietary management of IGT.