Antioxidant and anti-inflammatory functional foods for the management of type 2 diabetes: a systematic review

Background: Diabetes mellitus (DM) refers to a group of metabolic diseases characterized by reduced insulin synthesis and release, leading to hyperglycemia, oxidative stress, and inflammation. The prevalence of DM continues to increase worldwide, primarily driven by type 2 DM (T2DM). While numerous prescription drugs are widely available for the management of T2DM, these treatments must be coupled with significant changes in diet and lifestyle to have long-term effects. This comparative review aims to summarize and critically evaluate some of the dietary antioxidant and anti-inflammatory functional foods (FFs), including bioactive compounds on glycemic regulation, oxidative stress, inflammatory markers, and other outcomes in T2DM patients. Methods: A comprehensive literature search was performed from June 2014 to December 2025 in Cochrane Library, Embase, Google Scholar, PubMed/Medline, and Scopus databases. Results: Thirty-one meta-analyses describing the effects of specific FFs on glycemic outcomes, including fasting blood glucose, HbA1c, insulin levels, insulin resistance, oxidative or inflammatory stress, and/or the doses needed to achieve these endpoints, in T2DM patients were included. Comparative analyses of the data for green tea in T2DM showed significant antioxidant effects, but conflicting data for glycemic regulation, and no significant effect on inflammatory markers. Flaxseed products significantly reduced oxidative stress and HbA1c but had no anti-inflammatory effects. Both anthocyanins and resveratrol from fruits and vegetables significantly reduced fasting blood glucose, HbA1c, as well as oxidative and inflammatory markers. Turmeric and curcumin significantly reduced fasting blood glucose, but the data for ginger were conflicted. In T2DM patients, turmeric and ginger significantly reduced markers of oxidation and inflammation. Discussion: Overall, improvements in diet, including the incorporation of specific FFs and exercise, along with standard treatments, may be cost-effective methods to reduce the public health impact of T2DM. Limitations included the significant heterogeneity, high risk of bias, and low to moderate quality of the randomized controlled trial (RCT).