Cooking and co-ingested polyphenols reduce in vitro methylmercury bioaccessibility from fish and may alter exposure in humans

Abstract

Fish consumption is a major pathway for mercury exposure in humans. Current guidelines and risk assessments assume that 100% of methylmercury (MeHg) in fish is absorbed by the human body after ingestion. However, a growing body of literature suggests that this absorption rate may be overestimated. We used an in vitro digestion method to measure MeHg bioaccessibility in commercially-purchased fish, and investigated the effects of dietary practices on MeHg bioaccessibility. Cooking had the greatest effect, decreasing bioaccessibility on average to 12.5±5.6%. Polyphenol-rich beverages also significantly reduced bioaccessibility to 22.7±3.8% and 28.6±13.9%, for green and black tea respectively. We confirmed the suspected role of polyphenols in tea as being a driver of MeHg's reduced bioaccessibility, and found that epicatechin, epigallocatechin gallate, rutin and cafeic acid could individually decrease MeHg bioaccessibility by up to 55%. When both cooking and polyphenol-rich beverage treatments were combined, only 1% of MeHg remained bioaccessible. These results call for in vivo validation, and suggest that dietary practices should be considered when setting consumer guidelines for MeHg. More realistic risk assessments could promote consumption of fish as a source of fatty acids, which can play a protective role against cardiovascular disease.

Leaf extracts from Dendropanax morbifera Léveille mitigate mercury-induced reduction of spatial memory, as well as cell proliferation, and neuroblast differentiation in rat dentate gyrus

“…They observed analyzed 22 phenolic compounds in DML from green and senescent leaves [24] and we selected most abundant polyphenols in the present study and observed rutin and chlorogenic acid are most abundant in the DML. This result was supported by previous studies that rutin could decrease MeHg bioaccessibility in vitro digestion experiment [44]. Chlorogenic acid protects hippocampal neurons from aluminum-induced cytotoxicity by antioxidant actions [45].…”

Co-administration of a Rhododendron tomentosum extract does not affect mercury tissue concentrations and excretion rate in methylmercury-treated adult male rats

“…Although the lower fecal excretion rates and higher blood mercury levels observed in antibiotics-treated rats were attributed to the inhibition of MeHg demethylation by gut bacteria, other mechanisms such as perturbation of enzymatic activities in the liver (Table 1) or in other tissues, and alteration of gut barrier permeability [39] may also have contributed to these observations. Likewise, phytochemicals may also affect MeHg toxicokinetics through similar mechanisms, in addition to modulation of gut microbiota [19–21] and MeHg chelation [9, 11, 40]. Generalization of our conclusions to other teas, fruits and vegetables should be avoided, as phytochemicals absent from Labrador Tea but present in other herbal decoctions, and dietary fibers in fruits and vegetables may affect MeHg absorption, distribution, metabolism and excretion [11, 41].…”

“…Although epidemiology studies clearly link increased mercury levels in human tissue samples to fish and seafood consumption, correlation coefficients between estimated MeHg dietary intakes and body burdens are usually weak, ranging from 0.3 to 0.4 [1, 2]. These relatively weak correlations have been attributed to mercury quantification issues, dietary survey imprecisions, recall biases [2, 3], impaired liver functions [4, 5], genetic polymorphisms [6, 7], cooking methods [8, 9], and dietary interactions [6, 8–12]. A better understanding of the factors affecting MeHg absorption, distribution, metabolism and excretion may contribute to a refinement of risk assessments, regulatory guidelines and mitigation strategies.…”

Assessment of In Vitro Bioaccessibility and In Vivo Oral Bioavailability as Complementary Tools to Better Understand the Effect of Cooking on Methylmercury, Arsenic, and Selenium in Tuna

“…Despite this, recent studies have started to propose changes in consumption guidelines on the basis of in vitro bioaccessibility results alone [26,27]. Furthermore, numerous in vitro studies have reported that the cooking of fish muscle induced a significant reduction of Hg and MeHg bioaccessibility, which suggest a decreased MeHg solubility [26,[28][29][30]. If this phenomenon can be confirmed in vivo, current consumption guidelines could be modified.…”