Long-chain n-3 PUFA: plant v. marine sources.
Level 5 - mechanism / opinion, no new human data
Narrative review of tracer and feeding studies without systematic review methodology reported
PubMed 16441943 · doi:10.1079/pns2005473
What was done
This narrative review evaluated human feeding trials and stable-isotope tracer studies to assess the capacity of dietary plant-derived alpha-linolenic acid (alphaLNA) to convert to the long-chain n-3 polyunsaturated fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) via the elongation-desaturation pathway.
What was found
In adult men, conversion of alphaLNA to EPA was limited to approximately 8%, and fractional conversion to DHA was extremely low at less than 0.1%. In women, fractional conversion to DHA was substantially higher at approximately 9%, potentially mediated by lower beta-oxidation of alphaLNA or estrogen-mediated upregulation of Delta6-desaturase.
Why it matters
Because conversion of plant-based precursor n-3 fatty acids to DHA is extremely poor in men, plant sources such as rapeseed or soybean oils cannot readily substitute for marine sources to meet human long-chain n-3 PUFA requirements.
Limits
The abstract is a narrative review that does not report total sample sizes, search strategy, or specific inclusion criteria. Stated estrogen-mediated mechanisms in pregnant and lactating women were unconfirmed hypotheses at the time of publication.
Cited by
- context Estrogen increases the conversion of ALA into EPA and DHA by up to 20%.