Quality and sources of food and water consumed by people with chronic kidney disease of unknown etiology in Sri Lanka: a systematic review

Uthayarajan et al. (2025) present a systematic review of 57 studies (screened from 1,067 records, databases searched through 21 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 as the third most frequently listed contaminant.

Key numbers

Studies included: 57 of 1,067 (MEDLINE, EMBASE, PsycINFO, SLJOL, inception to 21 August 2024).

Metals detected in food in CKDu-endemic areas (number of studies):

• Cadmium: 14 studies (most frequently reported)
• Lead: 10 studies
• Arsenic: third most frequently reported; the review’s citation list corresponds to nine food-quality 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, kurakkan, 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), and black tea categories. In the review table, the black-tea rows are fluoride/major-ion evidence, not heavy-metal occurrence evidence.

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, packaged, TRI-site, MMU grade, oven-dried tea, and tea infusions) were assessed in the review, but the table reports fluoride/major-ion findings rather than cadmium occurrence for tea.

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: This review provides source-level context for Sri Lanka CKDu-endemic food and water matrices, especially rice, vegetables, freshwater fish, and drinking water. It identifies Cd as the most frequently reported nephrotoxic food contaminant in the included studies, but it does not provide pooled concentrations.

Courses: Illustrates how chronic dietary and drinking-water heavy-metal exposure is evaluated in endemic kidney-disease investigations, while preserving the review’s causal caution.

App: Treat Sri Lanka-origin rice, vegetables, freshwater fish, and drinking-water findings from this review as qualitative context pending primary-study extraction. Tea appears in this review primarily as fluoride/major-ion context, not as a heavy-metal occurrence anchor.

Wiki pages this source may touch

• cadmium
• lead
• arsenic-total
• aluminum
• chromium
• nickel
• tin
• mercury-total
• manganese
• zinc
• copper
• iron
• cobalt
• vanadium
• rice
• freshwater-fish
• vegetables
• lentils
• water
• fresh-fish

Verification notes

• Cross-vendor audit (Codex, 2026-05-17) corrected the publication to Journal of Nephrology, set the open-access license to CC BY 4.0 from the PDF license statement, removed unsupported inorganic-arsenic routing, corrected the arsenic study-count wording, and removed unsupported tea-cadmium claims.
• Strict Part 12 recheck found no sampled-product brand names. The source phrase “branded/packed tea” was generalized to packaged tea; TRI and MMU are institutional/grade descriptors in the source table rather than sampled-product brands.
• The review is a qualitative synthesis with no pooled concentration estimates. Do not promote its review-level findings to structured contamination profiles without extracting the cited primary studies.

Page history

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