Using wastewater surveillance to explore community-level dietary intake in sewered and non-sewered sanitation systems in Malawi, Africa

Wastewater can be used to measure biomarkers that reflect population-level dietary intake and diversity; however, how this approach may apply in a low-income country remains a knowledge gap. This study aims to evaluate whether select dietary-related metabolites can be detected in wastewater and environmental surveillance (WES) samples from both sewered and non-sewered sanitation systems in Malawi, Africa. Fourteen WES samples were collected and analyzed from two university campuses in Mzuzu and Thyolo, Malawi. Four targets were analyzed: N-methyl-2-pyridone-5-carboxamide (2PY; a biomarker of vitamin B3), 4-pyridoxic acid (4-PA; a biomarker of vitamin B6), as well as enterodiol and enterolactone (biomarkers of dietary fiber and polyphenol consumption). An 18-question survey, paired spatiotemporally with the WES measurements, assessed self-reported daily dietary intake, food insecurity, and nutrient deficiency symptoms among 500 respondents. Among the 14 WES samples, 2PY, 4-PA, and enterolactone were detected, while enterodiol was not detected above the method limit (<0.3 mg/kg). Most respondents (79%; 397/500) reported consuming foods associated with the 2PY biomarker. Many respondents (62%; 311/500) also reported consuming foods linked to the 4-PA biomarker. Fewer respondents (36%; 181/500) reported consuming foods associated with enterodiol or enterolactone, such as whole grains (e.g., millet) and other fiber-rich plant foods (e.g., beans, chickpeas, or pigeon peas). This study demonstrates the potential feasibility of monitoring dietary-related metabolites in both sewered and non-sewered sanitation systems in a low-income country to augment community-level nutrition data. 2PY, 4-PA, and enterolactone were detectable in WES samples, supporting the advancement of this emerging field in nutrition and food security research.