A Critical Review of Antidiabetic Properties of Tempeh From Various Substrates.

Tempeh is a traditional fermented food from several countries, especially Indonesia, with increasing recognition as a functional food candidate for managing type 2 diabetes mellitus (T2DM) due to its fermentation-enhanced bioactive compounds, including isoflavones, polyphenols, γ-aminobutyric acid, and bioactive peptides. This literature review synthesizes in vitro and in vivo studies retrieved from PubMed, ScienceDirect, and Google Scholar using the keywords "tempeh," "antidiabetic," "diabetes mellitus," "in vitro," and "in vivo" focusing on experimental designs evaluating biochemical, histological, and metabolic outcomes relevant to glycemic regulation. The proposed antidiabetic mechanisms of tempeh involve the inhibition of α-amylase and α-glucosidase to attenuate postprandial hyperglycemia, improvement of insulin secretion and sensitivity via AMPK activation, reduction of oxidative stress through enhanced antioxidant enzyme activity, and modulation of gut microbiota composition. Soybean tempeh consistently demonstrates hypoglycemic effects, β-cell regeneration, and increased hepatic glycogen storage in diabetic animal models. Non-soy variants, such as mung bean, pigeon pea, velvet bean, quinoa, sacha inchi, and komak bean tempeh, also exhibit glucose-lowering activity with additional benefits, including lipid profile improvement, nephroprotection, anti-inflammatory effects, and enhanced antioxidant capacity. Fermentation time, substrate type, and starter culture modification, particularly co-inoculation with lactic acid bacteria, influence the bioactive profile and potency. Collectively, these findings suggest that the diverse bioactive compounds in tempeh act through complementary metabolic and cellular pathways, making it a promising dietary intervention for T2DM prevention and management.