Internal exposure to heat-induced food contaminants in omnivores, vegans and strict raw food eaters: biomarkers of exposure to 2- and 3-monochloropropanediol (urinary excretion) and glycidol (hemoglobin adduct N-2,3-dihydroxypropyl-Val).

Fatty acid esters of 2/3-monochloropropanediol (2/3-MCPD) and glycidol are formed mainly during heat processing (deodorization) of vegetable oils, and are hydrolyzed by lipases in the gastrointestinal tract leading to the absorption of 2/3-MCPD and glycidol. The International Agency for Research on Cancer (IARC) has classified 3-MCPD as possibly and glycidol as probably carcinogenic to humans. The aims of the current work were to clarify the exposure to 2/3-MCPD and glycidol associated with different dietary habits (omnivore, vegan, raw-food eating), and the exposure development between 2017 and 2021 in German study participants. The questions were addressed using the daily urinary excretion of 2/3-MCPD and the hemoglobin adduct N-(2,3-dihydroxypropyl)-Val (DHP-Val) formed from glycidol as biomarkers of exposure, which were determined in two dietary studies including 36 omnivores, 36 vegans and 16 strict raw food eaters (abstaining from any heated food for at least four months). The median urinary excretion of 2- and 3-MCPD in non-smoking omnivores and vegans was 0.87 and 1.35 µg/day (2-MCPD), respectively, and 0.79 and 1.03 µg/day (3-MCPD), respectively. The 2/3-MCPD concentrations in urine samples of raw food eaters were usually below the limit of detection. The median DHP-Val levels in non-smoking vegans and omnivores were 3.9 pmol/g Hb each, and 1.9 pmol/g Hb in raw food eaters. Between 2017 and 2021, the exposure to 3-MCPD and glycidol did not change, however, the median 2-MCPD excretion decreased (p = 0.02, omnivores and vegans combined). The correlation between daily excretions of 2/3-MCPD determined 4 years apart was weak, whereas a moderate correlation was observed for DHP-Val (r(S) = 0.66) in this timeframe. In conclusion, the exposure to glycidol in omnivores and vegans was alike, whereas the 2/3-MCPD exposure was somewhat (albeit not significantly) higher in vegans. While 2/3-MCPD were hardly detectable in urine samples of raw food eaters, the median DHP-Val level (about 50% of those in omnivores) indicates a glycidol source independent of the dietary exposure.