Uthayarajan et al. (2025) present a systematic review of 57 studies (screened from 1,067 records, databases searched through August 2024) examining the quality of food and water consumed by people with chronic kidney disease of unknown etiology (CKDu) in Sri Lanka. CKDu is highly prevalent in Sri Lanka’s North Central Province and is suspected to be associated with nephrotoxic heavy metal and fluoride contamination via food and water. The review found that food — including rice, other cereals, legumes, bread, animal source foods, eggs, freshwater fish, fruit, and vegetables — was commonly contaminated with Cd, Pb, As, Mn, Zn, Cu, Fe, Cr, Se, Co, Al, Hg, Sn, K, Na, Mg, Ni, Ca, and V; cadmium was the most frequently reported nephrotoxic metal (detected in 14 studies), followed by lead (10 studies) and arsenic (10 studies).
Key numbers
Studies included: 57 of 1,067 (MEDLINE, EMBASE, PsycINFO, SLJOL, inception to August 2024).
Metals detected in food in CKDu-endemic areas (number of studies):
- Cadmium: 14 studies (most frequently reported)
- Lead: 10 studies
- Arsenic: 10 studies
- Other metals detected: Mn, Zn, Cu, Fe, Cr, Se, Co, Al, Hg, Sn, Ni, Ca, V, K, Na, Mg
Food matrices examined: rice (polished, unpolished, parboiled), maize, pulses and legumes (mung, cowpea, kurukkan, soya bean, undu), bread, animal source foods, eggs, freshwater fish (Nile tilapia Oreochromis niloticus, butter catfish), cows’ milk, fats and oil, lotus rhizome, fruits, vegetables (leafy, stem, root, coconut, yams), black tea (multiple grades).
Key findings from individual constituent studies:
- Cd in rice samples: chronic Cd and Cr exposure may result in kidney failure; rice Cd and Cr were significant concerns.
- As in rice: Cd, Pb, and Cr in rice were not significantly associated with CKDu occurrence in two studies; chronic Pb and Cd exposure was a public health concern in one study while As was within safe limits.
- Freshwater fish: inland fish (Nile tilapia, butter catfish) were contaminated with Cd; high Cd in fish was associated with CKDu prevalence rate.
- Tea: black tea samples (loose, branded, TRI site, MMU grade) were assessed; cadmium reported among contaminants.
No quantitative pooled concentration estimates are provided in this review (high heterogeneity prevented meta-analysis); the review is a qualitative synthesis summarizing study conclusions.
Methods (brief)
Systematic review following PRISMA guidelines. Databases: MEDLINE, EMBASE, PsycINFO, SLJOL, searched from inception to August 2024. Inclusion: studies on food/water quality in Sri Lankan CKDu-endemic areas, adults (excluding children, pregnant women, dialysis patients). Two independent reviewers with consensus for conflicts. Narrative synthesis; no meta-analysis due to high study heterogeneity. Data presented as summary tables.
Limitation: This is a systematic review of the CKDu literature, not a primary occurrence study. Concentration values for individual food items were reported inconsistently across primary studies and cannot be extracted as pooled figures from this source alone.
Implications
Certification: Sri Lanka-sourced rice, freshwater fish, and tea carry Cd, Pb, and As contamination signals relevant to HMT&C. The review provides context for Cd as the dominant nephrotoxic concern in South Asian rice systems.
Courses: Illustrates how chronic dietary heavy metal exposure (particularly Cd from rice) may drive endemic kidney disease — a powerful case for population-level risk from sub-threshold, long-duration exposure.
App: Sri Lanka provenance flag for rice and freshwater fish: Cd elevated (epidemiological association). Tea from Sri Lanka: Cd contamination reported in literature.