Omega-3, omega-6 and total dietary polyunsaturated fat on cancer incidence: systematic review and meta-analysis of randomised trials

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Omega-3, omega-6 and total dietary polyunsaturated fat on cancer incidence: systematic review and meta-analysis of randomised trials

Hanson et al., 2020 | Br J Cancer | Meta Analysis

Citation

Hanson Sarah, Thorpe Gabrielle, ... Hooper Lee. Omega-3, omega-6 and total dietary polyunsaturated fat on cancer incidence: systematic review and meta-analysis of randomised trials. Br J Cancer. 2020-Apr;122(8):1260-1270. doi:10.1038/s41416-020-0761-6

Abstract

BACKGROUND: The relationship between long-chain omega-3 (LCn3), alpha-linolenic acid (ALA), omega-6 and total polyunsaturated fatty acid (PUFA) intakes and cancer risk is unclear. METHODS: We searched Medline, Embase, CENTRAL and trials registries for RCTs comparing higher with lower LCn3, ALA, omega-6 and/or total PUFA, that assessed cancers over ≥12 months. Random-effects meta-analyses, sensitivity analyses, subgrouping, risk of bias and GRADE were used. RESULTS: We included 47 RCTs (108,194 participants). Increasing LCn3 has little or no effect on cancer diagnosis (RR1.02, 95% CI 0.98-1.07), cancer death (RR0.97, 95% CI 0.90-1.06) or breast cancer diagnosis (RR1.03, 95% CI 0.89-1.20); increasing ALA has little or no effect on cancer death (all high/moderate-quality evidence). Increasing LCn3 (NNTH 334, RR1.10, 95% CI 0.97-1.24) and ALA (NNTH 334, RR1.30, 95% CI 0.72-2.32) may slightly increase prostate cancer risk; increasing total PUFA may slightly increase risk of cancer diagnosis (NNTH 125, RR1.19, 95% CI 0.99-1.42) and cancer death (NNTH 500, RR1.10, 95% CI 0.48-2.49) but total PUFA doses were very high in some trials. CONCLUSIONS: The most extensive systematic review to assess the effects of increasing PUFAs on cancer risk found increasing total PUFA may very slightly increase cancer risk, offset by small protective effects on cardiovascular diseases.

Key Findings

We included 47 RCTs (108,194 participants). Increasing LCn3 has little or no effect on cancer diagnosis (RR1.02, 95% CI 0.98-1.07), cancer death (RR0.97, 95% CI 0.90-1.06) or breast cancer diagnosis (RR1.03, 95% CI 0.89-1.20); increasing ALA has little or no effect on cancer death (all high/moderate-quality evidence). Increasing LCn3 (NNTH 334, RR1.10, 95% CI 0.97-1.24) and ALA (NNTH 334, RR1.30, 95% CI 0.72-2.32) may slightly increase prostate cancer risk; increasing total PUFA may slightly inc

Outcomes Measured

  • Requires manual extraction

Population

Field Value
Population See abstract
Sample Size 108194
Age Range See abstract
Condition See abstract

MeSH Terms

  • Fatty Acids, Omega-3
  • Fatty Acids, Omega-6
  • Fatty Acids, Unsaturated
  • Humans
  • Incidence
  • Neoplasms
  • Randomized Controlled Trials as Topic
  • Risk
  • alpha-Linolenic Acid

Evidence Classification

  • Level: Meta Analysis
  • Publication Types: Journal Article, Meta-Analysis, Research Support, Non-U.S. Gov't, Systematic Review
  • Vertical: omega-3

Provenance

Source extracted via PubMed E-utilities API on 2026-04-09