Brum et al. 2025 — Essential elements and PTEs in organic vs conventional flaxseeds

This study quantified 20 chemical elements (11 essential, 9 PTEs) in 52 commercially available European flaxseed samples using ICP-OES, comparing organic (n=15) and conventional (n=37) seeds. Three elements showed statistically significant differences (p < 0.05) between organic and conventional samples: Al and Ni were higher in conventional flaxseeds (p = 0.0312 and p = 0.0142, respectively), while Na was higher in organic flaxseeds (p = 0.0072). Pb and Cd concentrations did not differ significantly between organic and conventional groups. Cadmium concentrations in both groups remained well below the EU Regulation 2023/915 maximum level of 0.50 mg/kg for linseeds. Hazard Index modelling showed that Al and Pb pose the more pressing health risk at typical consumption levels of 15–30 g/day; Cd HI values remained below 1 in all scenarios.

Key numbers

Concentrations from Table 2 (mg/kg dry weight, mean / minimum / maximum):

Organic flaxseeds (n=15):

• Al: mean 6.015 mg/kg; range 0.226–23.654 mg/kg (statistically lower than conventional, p = 0.0312)
• Cd: mean 0.116 mg/kg; range 0.043–0.290 mg/kg; below EU ML of 0.50 mg/kg
• Pb: mean 0.368 mg/kg; range 0.015–1.654 mg/kg (difference vs conventional not significant)
• Ni: mean 0.652 mg/kg; range 0.219–2.104 mg/kg (statistically lower than conventional, p = 0.0142)
• Cr (total): mean 0.113 mg/kg; range 0.047–0.168 mg/kg

Conventional flaxseeds (n=37):

• Al: mean 8.940 mg/kg; range 0.326–21.469 mg/kg (higher than organic, p = 0.0312)
• Cd: mean 0.127 mg/kg; range 0.033–0.578 mg/kg; below EU ML
• Pb: mean 0.286 mg/kg; range 0.015–2.762 mg/kg
• Ni: mean 0.976 mg/kg; range 0.105–2.667 mg/kg (higher than organic, p = 0.0142)
• Cr (total): mean 0.249 mg/kg; range 0.030–2.168 mg/kg

Other elements measured (Table 2, mean mg/kg dry weight, organic | conventional): Ca 2866.142 | 3199.202; Co 3.963 | 5.509; Cu 11.407 | 11.035; Fe 35.296 | 41.098; K 7685.005 | 7348.621; Mg 6733.650 | 6140.583; Mn 15.745 | 16.428; Mo 3.204 | 4.621; Na 1182.777 | 898.004 (Na higher in organic, p = 0.0072); Zn 37.739 | 38.714; B 11.469 | 10.099; Ba 1.210 | 1.158; Li 1.835 | 1.951; Sr 6.452 | 6.394; V 0.033 | 0.033.

Hazard Index (HI) at 15 g/day flaxseed intake (organic | conventional):

• Al: 3.22 | 4.79 (both > 1)
• Pb: 789.15 | 612.01 (both ≫ 1)
• All other elements (Cd, Cr, Co, Cu, Mn, Mo, B, Ba, Li, Ni, Sr, V): HI < 1

Hazard Index at 30 g/day flaxseed intake (organic | conventional):

• Al: 6.45 | 9.58
• Pb: 1,578.3 | 1,224.02

Estimated daily intake of Cd (Table 3, mg/kg bw/day, 15 g/day | 30 g/day):

• Organic: 2.49 × 10⁻⁵ | 4.99 × 10⁻⁵
• Conventional: 2.72 × 10⁻⁵ | 5.45 × 10⁻⁵

Estimated daily intake of Pb (Table 3, mg/kg bw/day, 15 g/day | 30 g/day):

• Organic: 7.89 × 10⁻⁵ | 1.58 × 10⁻⁴
• Conventional: 6.12 × 10⁻⁵ | 1.22 × 10⁻⁴

Reference doses used (Table 1, USEPA Regional Screening Levels): Al RfD = 4 × 10⁻⁴ mg/kg/day; Cd RfD = 1 × 10⁻³ mg/kg/day; Cr RfD = 3 × 10⁻³ mg/kg/day; Ni RfD = 2 × 10⁻² mg/kg/day; Pb RfD = 1 × 10⁻⁷ mg/kg/day. The Pb RfD value drives the extreme Pb HI; readers should interpret Pb HI in the context that USEPA does not formally publish a Pb oral RfD because there is no recognised safe level, and the value used here is a derived screening level rather than a canonical RfD.

EU regulatory context: EU Regulation 2023/915 (which superseded EC 1881/2006) sets a maximum level of 0.50 mg/kg for Cd in linseeds (flaxseeds); no EU maximum levels exist for Pb, Al, or Ni in flaxseeds or oilseeds more broadly as of the study date.

Exposure model parameters: EDI computed with BW = 70 kg, EF = 365 days/year, ED = 25 years, DI = 15 or 30 g/day. The 3.5 g/day intake threshold for keeping Al HI below 1 is cited in the Discussion as the maximum permissible flaxseed intake for Al alone; the authors note Pb HI would still exceed 1 at that intake.

Sample structure: 52 commercial flaxseed samples (15 organic, 37 conventional) sourced from EU supermarkets, herbalists, and online stores. Triplicate analysis (5 g per replicate). Reporting basis is dry weight after ashing.

Methods (brief)

Inductively coupled plasma–optical emission spectrometry (ICP-OES) using a Thermo Scientific iCAP PRO ICP-OES autosampler (Waltham, MA, USA). Sample preparation: 5 g aliquots in triplicate were weighed into porcelain capsules (Staatlich, Berlin, Germany), oven-dried (Nabertherm, Lilienthal, Germany) at 80 °C for 24 h, then ashed in a muffle furnace (Nabertherm) at 450 °C with temperature gradually increased over the first 24 h and held for an additional 48 h (72 h total). Ash was treated with 65% HNO₃ (Sigma-Aldrich, Taufkirchen, Germany) for 24 h, then diluted to 25 mL in 1.5% HNO₃ in distilled water. Certified reference materials were used for QC. LOD/LOQ were derived from 15 blanks under reproducibility conditions per IUPAC nomenclature; instrument operational parameters, recovery percentages, detection limits, quantification limits, and wavelengths are tabulated in Supplementary Tables S1 and S2 (not extracted into this page). Statistical analysis used t-tests and Mann–Whitney tests (selection based on Kolmogorov–Smirnov normality test) in GraphPad Prism 8.2.1.

Speciation: No arsenic or mercury speciation was performed. Arsenic and mercury were not among the 20 elements quantified in this study. Chromium was measured as total Cr; no Cr-VI speciation was performed.

Implications

This source contributes occurrence data for Al, Cd, Cr (total), Ni, Pb, and 15 additional elements in European commercial flaxseed samples, with organic versus conventional comparisons. The contamination profile is dry-weight basis at the seed (as-purchased) form.

Notable for downstream synthesis: (1) the organic-versus-conventional comparison shows that the assumption of lower contamination in organic seeds does not hold uniformly across metals — for Al and Ni the conventional samples carry higher mean concentrations, while for Na the organic samples are higher; for Pb and Cd the difference is not statistically significant in this dataset; (2) Pb HI values in the 600–1,600 range arise from the USEPA-derived RfD rather than from extreme Pb concentrations (the means of 0.286–0.368 mg/kg are within the range typical of oilseed literature), so the HI magnitude is a property of the toxicological reference and should not be read as a measured intake exceedance of an established standard; (3) the EU regulatory gap — Cd is the only contaminant with a flaxseed-specific maximum level under EU 2023/915 — is documented in the Discussion.

Wiki pages this source may touch

• flaxseeds
• lead
• aluminum
• nickel
• cadmium
• chromium
• eu-2023-915-cadmium

Verification notes

Merge-enhanced 2026-05-25 from a pre-existing 2026-05-14 page that contained catastrophic value transpositions and one incorrect statistical claim:

1. Al organic mean was 2,040.609 µg/kg (which is in fact the Ca organic minimum from Table 2); corrected to 6.015 mg/kg.
2. Al conventional mean was 3,890.695 µg/kg (which is in fact the Ca organic maximum); corrected to 8.940 mg/kg.
3. Pb organic mean was 0.652 mg/kg (which is in fact the Ni organic mean); corrected to 0.368 mg/kg.
4. Pb conventional mean was 0.249 mg/kg (which is in fact the Cr conventional mean); corrected to 0.286 mg/kg.
5. Ni organic mean was 0.368 mg/kg (which is in fact the Pb organic mean); corrected to 0.652 mg/kg.
6. Ni conventional mean was 0.638 mg/kg; corrected to 0.976 mg/kg.
7. Cr conventional mean was 0.048 mg/kg (which is in fact the Co organic minimum); corrected to 0.249 mg/kg.
8. Headline claimed “organic flaxseeds had statistically significantly higher Pb concentrations than conventional samples” — this is false. The paper’s asterisks and Discussion identify three statistically significant differences: Al higher in conventional (p = 0.0312), Ni higher in conventional (p = 0.0142), Na higher in organic (p = 0.0072). Pb and Cd differences between groups are not statistically significant.

Other enhancements:

• Added raw_sha256 of the source PDF; corrected raw_handle from generic manual-fetch-kimi to PDF-specific MFK_p0304-assessment-of-essential-elements-and-potenti; corrected raw_path to full original filename.
• Added complete element panel summary to Key numbers (all 20 elements, mean concentrations).
• Added explicit EDI values for Cd and Pb from Table 3.
• Added Reference Dose values from Table 1 with note explaining the USEPA Pb RfD context driving extreme Pb HI values.
• Added regulation slug reference eu-2023-915-cadmium (the regulation explicitly named in Discussion).
• Removed Part 2 wiki/HMTc-firewall borderline content from prior Implications section (cross-source synthesis comparison to “peanut Pb levels” and forward-looking HMT&C threshold-setting language); replaced with what-this-source-contributes framing per Part 2.
• Removed inline µg/kg parenthetical conversions that risked silent unit drift; values reported in the paper’s native mg/kg dry-weight basis throughout.

Audit subagent (2026-05-25) verdict REVISE; two ⚠️ findings reviewed:

• Check 2: ingredients/flaxseeds slug not yet in docs/gpt-collaboration/taxonomy-snapshot.md (snapshot dated 2026-05-18). Verified against wiki/ingredients/ — no flaxseeds.md page exists yet, and three source pages now reference the slug (brum2025, lee2019, nazari2023). The slug therefore qualifies for the ≥freq-2 auto-stub via tools/autonomy/create-missing-pages.mjs per CLAUDE.md Part 10. Action: leave the slug in place; the auto-stub will create the ingredient page and the taxonomy snapshot will pick it up on its next regeneration. No correction needed.
• Check 2: matrices: [seed, oilseed] flagged as unconfirmed against a controlled matrices vocabulary. Verified — matrices vocabulary in docs/gpt-collaboration/system-prompt.md is documented as bare strings with broad-scope guidance rather than a closed list; oilseed is already in use in wiki/sources/lee2019-food-processing-heavy-metals-migration.md. False positive; no change.

All five audit checks otherwise clean (numerical fidelity verified across Tables 1/2/3 and the p. 5 HI narrative; speciation/methods accurate; brand firewall clean; wiki/HMTc firewall clean including Implications section).

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.