Exploring saliva as a biofluid for biomonitoring of diet-related contaminants exposure: insights from a literature mining approach

BACKGROUND: Human biomonitoring (HBM) is crucial for evaluating exposure to diet-related contaminants, whose effects may pose substantial health risks. Saliva is recognized as a promising non-invasive biological matrix due to its ease of collection and potential to reflect external and systemic exposure. However, suitability for monitoring dietary hazardous compounds remains uncertain. OBJECTIVE: To assess the potential of saliva as a biomonitoring matrix for diet-related contaminants, identify compounds with robust diet-related associations, and highlight knowledge gaps. METHODS: A systematic literature review was conducted to screen over 500 diet-related contaminants analyzed in saliva. Detailed information was extracted only for contaminants quantitatively measured in saliva, including concentration ranges, sample sizes, and analytical methods. Evidence of correlations with systemic concentrations, exposure pathways, and individual or lifestyle factors was compiled into a FAIR database to provide an integrated evaluation of saliva's biomonitoring potential. RESULTS: Only a limited subset of contaminant groups, including nitrite/nitrate, heavy metals, bisphenols, polycyclic aromatic hydrocarbons (PAHs), biogenic amines, pesticides, advanced glycation end products (AGEs), perchlorate, microplastics (MPs), parabens and phthalates, have been quantitatively measured in saliva. Compounds such as nitrate, arsenic, AGEs, pesticides and perchlorate demonstrate moderate to strong correlations between salivary and systemic levels, supporting saliva's potential to estimate exposure. Conversely, substances like PAHs, MPs, phthalates and parabens generally show weak or no correlation, reflecting recent or localised exposures rather than cumulative burden. Salivary composition is influenced by intrinsic and extrinsic factors, including diet, oral microbiota, physiology, and sampling conditions, resulting in high interindividual variability. SIGNIFICANCE: Despite challenges, low salivary concentrations and lack of standardized collection protocols, saliva offers advantages for biomonitoring vulnerable populations, such as children and pregnant women. Harmonized collection procedures, validated sensitive methods, predictive models accounting for variability and exposure context, could establish saliva as a reliable complementary or alternative matrix for assessing human exposure to dietary and environmental contaminants. IMPACT: This systematic review synthesizes findings from 104 studies, covering over 500 diet-related contaminants measured in saliva, and compiles them into a FAIR database, providing the most comprehensive resource to date for saliva-based biomonitoring. Compounds such as nitrate, arsenic, advanced glycation end-products (AGEs), pesticides, and perchlorate show meaningful correlations with systemic levels, supporting saliva's potential as a non-invasive matrix for assessing human exposure. To fully realize saliva's potential, standardized collection protocols, validated analytical methods, and predictive models that account for interindividual variability and exposure context are urgently needed, enabling more accurate and ethical monitoring of vulnerable populations.