Prediabetes Remission, Anthocyanins, and Heart Risk

Getting out of the prediabetes range may matter far beyond the next glucose test. Two long-running studies found that people who reached normoglycemia had lower rates of cardiovascular death or heart-failure hospitalization over the following 20 to 30 years. The finding is striking, but it does not prove that any supplement can deliver the same result.

That distinction frames the evidence on anthocyanins, the red-blue-purple plant pigments found in berries. A small double-blind trial found that a standardized anthocyanin supplement improved impaired glucose tolerance over 12 weeks. A separate crossover trial found that red raspberry, especially when paired with fructo-oligosaccharides (FOS), changed gut bacteria alongside favorable insulin-related measures. These are useful leads, not a replacement for exercise, dietary changes, weight management when appropriate, or medical care.

Why prediabetes remission has become a cardiovascular question

A 2026 post-hoc analysis of the US Diabetes Prevention Program Outcome Study and China's DaQing Diabetes Prevention Outcome Study linked prediabetes remission with substantially lower long-term cardiovascular risk. In the multiracial US cohort of 2,402 participants, those who achieved remission had a cardiovascular death or heart-failure hospitalization rate of 1.74 per 1,000 person-years, versus 4.17 among those who did not. Over a median 20 years, the fully adjusted hazard ratio was 0.41 (95% CI 0.20–0.84; p=0.014). In the 540-person Han Chinese DaQing cohort, followed for 30 years, the corresponding hazard ratio was 0.49 (95% CI 0.28–0.84; p=0.010). Read the 2026 DPPOS and DaQing analysis for the full definitions and methods.

The most intriguing result came from an "at least once remission" analysis. Participants who ever reached normoglycemia had a hazard ratio of 0.43 (95% CI 0.29–0.63; p<0.0001) for the composite outcome, even if their glucose later rose again. That pattern fits the idea of a metabolic legacy effect: time spent with healthier glucose regulation may have durable consequences.

Still, these are observational, post-hoc analyses rather than trials designed with cardiovascular events as the primary endpoint. Statistical adjustment, including inverse probability weighting, can address measured differences between groups; it cannot fully erase the possibility that people who remitted were healthier in ways the analysis missed. Only 11.5% of DPPOS participants achieved remission, which also raises the possibility of healthy-responder bias. The studies show a strong association, not proof that transient remission itself caused the lower event rate.

An anthocyanin trial produced a promising secondary result

The most direct supplement evidence comes from a 12-week, randomized, double-blind, placebo-controlled trial of 68 Chinese adults with impaired glucose tolerance (IGT). Participants received either 160 mg per day of anthocyanins or placebo. IGT reverted in 55.9% of the anthocyanin group and 29.4% of the placebo group (p=0.013), according to Yu et al.'s 2026 trial. That is a meaningful difference in a clinical glucose category, although the study was too short to show whether the change lasted after treatment ended.

The insulin-sensitivity result points in the same direction. The Matsuda index improved by a mean 4.6 units with anthocyanins (95% CI 2.5–6.7; p=0.003). Skin advanced glycation end-products, measured by autofluorescence, fell significantly only in the treatment group. Lower skin AGE readings correlated with lower postprandial glucose area under the curve (r=0.302; p=0.001) and with a higher Matsuda index (r=−0.344; p<0.001).

Those correlations make reduced glycation burden a plausible explanation worth testing. They do not establish a biological chain in humans. Skin autofluorescence can also be influenced by skin pigmentation, smoking history, and UV exposure, so it is an imperfect proxy for systemic AGE burden.

More importantly, the trial missed its pre-specified primary endpoint. The adjusted difference in disposition index—a measure combining beta-cell function and insulin sensitivity—was 61.3, with a 95% CI from −27.4 to 150.0 (p=0.174). Because the confidence interval includes no difference and the endpoint was non-significant, the study did not demonstrate beta-cell restoration. The reversion and Matsuda findings were secondary outcomes, which need replication in a larger, pre-registered trial.

Raspberry and FOS changed microbes, but causality remains open

The gut microbiome story is more concrete than the usual "feed your bugs" sales copy, but it is still early. In a four-week randomized crossover trial of 26 adults with insulin-resistant prediabetes, red raspberry supplementation reduced hepatic insulin resistance by 30.1% (p=0.04). It also roughly doubled Eubacterium eligens and reduced Ruminococcus gnavus by about 60% (p≤0.05), as reported in Zhang et al.'s raspberry and FOS trial.

When researchers combined raspberry with FOS, a prebiotic fiber, the disposition index increased by 94.4% (p=0.04) and Bifidobacterium species increased about fourfold. Higher R. gnavus abundance correlated with higher hepatic insulin resistance, while E. eligens and Bifidobacterium catenulatum correlated with lower total cholesterol.

The experiment supports the claim that this dietary combination can shift microbial communities and metabolic markers over four weeks. It cannot show that the bacteria caused the metabolic changes. The trial was small, short, and vulnerable to the usual limits of crossover studies, including potential carry-over effects. A broader 2025 meta-analysis of microbiome-targeted therapies in type 2 diabetes also found improved glucose and inflammatory measures across randomized trials, but the field still lacks convincing human evidence that the observed microbial shifts are the causal driver rather than a fellow traveler.

How much does this apply outside these trials?

Anthocyanin findings are consistent with a 2024 meta-analysis of randomized trials in type 2 diabetes, which reported improvements in glycemic and cardiovascular biomarkers. That population had established diabetes, not prediabetes, and biomarkers are not cardiovascular events. A clinical trial of blood orange juice also linked changes in specific gut bacteria with cardiometabolic biomarkers, suggesting that the polyphenol-microbiome pattern is not unique to raspberries.

But isolated anthocyanins have not been compared head-to-head with metformin or intensive lifestyle intervention for prediabetes remission. A 2025 review of lifestyle interventions found that response varies by prediabetes phenotype. IGT is not identical to impaired fasting glucose, and results in an IGT-only cohort should not be casually applied to every person labeled prediabetic.

Dietary pattern also matters. A 2024 meta-analysis of plant-based diet trials found improved insulin-resistance markers in relevant populations, while a 2024 meta-analysis of aerobic-exercise trials found improvements in fasting glucose, HbA1c, BMI, and insulin-resistance measures in people with prediabetes. These approaches work through pathways not limited to anthocyanin metabolism, and no study has quantified what a berry extract adds to a comprehensive lifestyle program.

What the evidence supports now

Prediabetes remission is associated with markedly lower cardiovascular death and heart-failure hospitalization over decades in two independent cohorts. That makes remission a meaningful target, even though the causal explanation remains unsettled. One small double-blind trial found that 160 mg per day of anthocyanins increased IGT reversion and improved insulin sensitivity over 12 weeks, but it missed its primary endpoint and cannot establish long-term benefit. Raspberry plus FOS changed gut microbes and several metabolic measures in a 26-person, four-week trial; the microbial changes remain correlations.

If you have prediabetes, use this evidence as a reason to take glucose improvement seriously—not as a reason to treat a berry-pigment capsule as a cardiovascular-outcomes drug. Confirm the diagnosis and discuss an individualized plan with a clinician, especially if you use glucose-lowering medication or have cardiovascular disease.