Chen et al. 2023 — Heavy metals and inflammatory bowel disease
This narrative review synthesizes evidence on how heavy metal exposure — including lead (Pb), manganese (Mn), arsenic (As), cadmium (Cd), and mercury (Hg) — contributes to the pathogenesis and exacerbation of inflammatory bowel disease (IBD), encompassing Crohn’s disease and ulcerative colitis. The authors frame diet and drinking water as the dominant routes of human heavy metal exposure and trace the mechanistic pathways from exposure to intestinal inflammation, emphasizing gut dysbiosis, oxidative stress, barrier disruption, and immune activation.
Key numbers
Dietary sources highlighted: rice and cereals for inorganic arsenic; leafy vegetables and root crops for Pb and Cd; seafood for total mercury and MeHg. No new primary concentration measurements are reported; the paper aggregates published exposure and mechanistic data. The review does not report a defined sample size (it is a literature synthesis).
Metal-specific mechanistic findings reviewed:
- Pb: disrupts tight-junction proteins, alters gut microbiota composition, elevates pro-inflammatory cytokines (TNF-α, IL-1β, IL-6); associated with increased IBD incidence in epidemiological studies.
- Mn: essential at low doses, neurotoxic and pro-inflammatory at elevated dietary intake; manganism linked to gut microbiome shifts favoring pathobionts.
- As (inorganic): promotes intestinal oxidative stress and mitochondrial dysfunction; animal models show colitis exacerbation at concentrations relevant to drinking water and rice consumption.
- Cd: bioaccumulates in intestinal epithelium; induces apoptosis of enterocytes; disrupts mucosal immunity; multiple cohort studies cited associating urinary Cd with IBD incidence.
- Hg (total and methyl): disrupts intestinal barrier; alters bile acid metabolism; associated with increased intestinal permeability in animal models; dietary seafood identified as primary exposure route.
Methods (brief)
Narrative review. Literature sourced from PubMed and Web of Science through late 2022. Inclusion criteria: experimental and observational studies examining heavy metal exposure and IBD outcomes. No formal meta-analytic synthesis; qualitative summary of mechanistic and epidemiological evidence.
Implications
Certification: Supports HMT&C rationale for controlling Pb, Cd, iAs, and tHg across dietary categories, particularly for individuals with pre-existing gut conditions or genetic susceptibility to IBD. The gut barrier disruption and dysbiosis mechanisms documented here are relevant to cumulative-exposure frameworks.
Courses: Useful for the module on heavy metals and gut health; provides accessible mechanistic framing for Pb, Cd, As, and Hg across the IBD exposure pathway.
App: No per-ingredient concentration data; contributes to health endpoint framing but not contamination_profile population.
Microbiome: Directly relevant — reviews microbiota composition shifts, barrier disruption, and immune dysregulation for all five metals. Good anchor for wiki/microbiome pages on Pb-gut-axis, Cd-microbiome, and As-gut-barrier.