Abstract
L-Ergothioneine (L-EGT), a naturally occurring thiol compound abundant mainly in edible fungi, is increasingly regarded as a potentially beneficial bioactive constituent. However, population-level exposure data remain limited. This study aimed to estimate background dietary exposure to L-EGT among Chinese residents, describe its distribution across population subgroups and regions, identify major food contributors, and characterize the risk using a margin of exposure (MOE) approach. Individual body-weight-normalized L-EGT intakes were estimated from published food concentration data and three-day dietary recalls of 42,218 participants. MOEs were calculated using a no observed adverse effect level (NOAEL) of 800 mg/kg bw/d obtained from subchronic toxicity studies. The mean dietary exposure to L-EGT was 0.043 mg/kg bw/d (MOE = 18,605) in the general population and 0.174 mg/kg bw/d (MOE = 4598) among consumers, with 95th percentile exposures of 0.244 mg/kg bw/d (MOE = 3279) and 0.644 mg/kg bw/d (MOE = 1242), respectively. MOE values were consistently above the safety threshold of 300 across all subgroups, with less than 0.3% of the total population and 1.3% of consumers aged 3-6 years falling below this value. These results indicate that current natural dietary exposure to L-EGT in China is low and does not raise safety concerns and provide essential baseline data for future studies on its health effects, optimal intake ranges, and long-term safety.