Silva et al. 2025 — Edible oils: health benefits and contamination risks (systematic review)
This systematic review (35 included studies from MEDLINE/PubMed, ScienceDirect, and SCOPUS through September 2025) examines the health impacts, production methods, and contamination profiles of extra virgin olive oil, olive oil, soybean, palm olein, corn, and camellia seed oils, with a section specifically addressing heavy metal and PAH contamination. Seven of the 35 included studies focused on contaminants; the review synthesizes their findings alongside original concentration data from a broader appendix table (Table A1) drawing on additional published literature. The review concludes that heavy metals in edible oils are generally below regulatory thresholds but that environmental and agricultural conditions create meaningful regional variation, and that continued monitoring is warranted given proximity of some values to limits.
Key numbers
Compiled heavy metal concentrations in edible oils (Table A1, µg/kg, combining data from multiple cited sources):
- Olive oil: tAs 7.65–9.06; Cr 7.12–9.43; Cd 3.14–5.06; Ni 6.14–8.38; Zn 18.15–28.55; Cu 16.52–21.90; Pb 3.14–17.48; Fe 56.12; Mn 6.12
- Sunflower oil: tAs 0.55; Ni 1.20; Pb 0.67; Cu 3.23; Zn 69.60; Mn 2.29; V 0.15
- Soybean oil: tAs 1.58; Pb 1.12; Ni 0.96; Zn 111.09; Cu 4.44; Mn 1.96
- Rice bran oil (Iran): Pb 2.57; Cd 0.07; tAs 2.46; Ni 0.97; Zn 101.36; Cu 21.08; Mn 2.44
- Palm oil: tAs 2.8; Ni 10.08; Pb 2.01; Cr 5.36; Co 0.21; Cu 17.94; Zn 191.04; Mn 26.31; V 0.55
- Canola oil: tAs 0.67; Ni 0.27; Pb 1.03; Cu 9.82; Zn 65.36; Mn 0.89
- Flaxseed oil (Korea): Pb 25.65; Cd 70.03; tAs 3.10; Al 29,814 (µg/kg)
- Peanut oil: tAs 5–89*; Cd 6–9*; Pb 25–27*; Fe 5,655–11,323*; Zn 2,863–8,835*
- Sesame oil: tAs 64–91*; Cd 9*; Pb 9–13*; Fe 15,091–23,664*; Zn 3,192–6,299*
- Corn oil: Pb 19.27–32.40; Cd 4.48–5.77
- Rapeseed oil: Cd 1–7*; Pb 12–100*; tAs 1–10*; Hg <5–10*; Cu 36–55*; Fe 236–1,320*
*Values converted from mg/kg to µg/kg in original table.
Selected cited study findings:
- Extra virgin olive oil from Morocco (Bechar et al.): all metals within legal limits, regional variation from contaminated irrigation water, industrial emissions, mining proximity
- Rice bran oil from Iran (Mohajer et al.): metal levels near US EPA screening thresholds
- Olives from contaminated soils in Greece (Antoniadis et al.): Cd exceeded EU limit of 0.05 mg/kg; risks from tAs and Pb confirmed
- Traditional olive oil from Iran (Tayeb & Movassaghghazani, n=60): Pb and Cd below national limits; traditional olive oil showed MOE for Pb under 10,000; HI for both metals below 1
PAH concentrations (EU limit for sum of 4 PAHs: 2 µg/kg for oils):
- Camellia oil: 7.15 µg/kg; flaxseed: 8.62; peanut: 6.44; sesame: 6.31; corn: 6.08–182.79; canola: 129.28; palm: 22.6; sunflower: 5.63; olive: 5.39; soybean: 5.34
Methods
Systematic review following adapted PRISMA principles. Databases: MEDLINE/PubMed, ScienceDirect, SCOPUS through 1 September 2025. No language or date restrictions. Of 125 initially identified articles, 35 met eligibility (8 human studies, 2 animal studies, 18 on oil production/processing, 7 on contaminants). Risk of bias assessed using ROB2, ROBINS-I, and SYRCLE tools. The heavy metal data in Table A1 is a compiled reference table from cited studies, not a meta-analysis; some entries appear to conflate different sources and methods. Speciation is not uniformly reported; arsenic figures should be treated as total arsenic unless the primary source states otherwise.
Implications
Certification: Table A1 provides a useful multi-oil comparison benchmark for the HMT&C edible-oil workbench. The olive oil range (Pb 3.14–17.48 µg/kg; Cd 3.14–5.06 µg/kg) is consistent with well-controlled European production and provides a reasonably clean baseline. Flaxseed and sesame oils show substantially higher Pb and Cd concentrations in the tabulated data, a meaningful product-level risk contrast.
Courses: The review’s Table 3 and Table A1 provide a pedagogically useful cross-oil contamination comparison that can anchor module content on edible oil safety.
App: The tabulated ranges in Table A1 can be used as rough prior values for oil-type contamination profiles; however, the composite nature of the table (multiple underlying studies, unclear weighting) means these should be treated as indicative ranges rather than calibrated estimates.
Speciation caution: The review does not distinguish iAs from tAs in its heavy metals discussion. All arsenic figures from this source must be treated as total arsenic.