Azo-dye adulteration of palm oil: occurrence, detection, toxicological implications, and regulatory gaps

The fraudulent adulteration of palm oil with synthetic azo dyes, such as Sudan I–IV and Metanil Yellow, represents a critical, under-reported global public health crisis. Driven by economic arbitrage, illicit vendors utilize these industrial textile colorants to mask oil degradation and simulate a premium, carotene-rich aesthetic. While the immediate chemical fraud is well-documented, this review synthesizes the available mechanistic evidence on plausible insidious, multi-systemic physiological degradation associated with chronic dietary exposure to these dyes, even though, there is currently no direct human epidemiological confirmation. Azo-dyes undergo microbial reduction by enteric bacteria, cleaving their characteristic -N=N- bonds to generate highly carcinogenic aromatic amines. This process induces profound gut dysbiosis, degrading the mucosal barrier and driving systemic endotoxemia. Concurrently, these lipophilic compounds act as potent endocrine-disrupting chemicals (EDCs), destabilizing estrogen receptors and mimicking reproductive hormones. At the cellular level, xenobiotic detoxification overburdens hepatic and renal pathways, generating massive reactive oxygen species (ROS) that disrupt mitochondrial function, facilitating DNA adduct formation, and promote irreversible lipid peroxidation. Permeating the blood–brain barrier (BBB), dye metabolites further provoke neuroinflammation, potentially altering neurotransmitter synthesis via the gut-brain axis to impact mental health. On current evidence, vulnerable, low-income populations reliant on unbranded open-market staples bear a disproportionate share of exposure to these adulterants, though population-level health impact has not been directly quantified. Mitigating this crisis demands a paradigm shift: transitioning from standard laboratory chromatography to rapid, decentralized field-screening technologies, alongside stringent blockchain-backed supply chain traceability and aggressive policy enforcement. Ultimately, addressing azo-dye adulteration of palm oil requires an integrated framework combining advanced analytical chemistry, robust regulatory intervention, and widespread consumer education.