Changes in plasma fatty acids and related biomarkers during transition to an exclusively plant- and fish-based diet in healthy adults.

Objective: The aim of this study was to examine the time scale of plasma fatty acid changes during transition to an exclusively plant- and fish-based diet in healthy individuals and determine whether there are associated alterations in arachidonic acid (ARA)-derived inflammatory mediators, estimated stearoyl coenzyme A desaturase (SCD) activity, and blood pressure.

Methods: In pursuit of a religious fast, 36 adults abstained  from eating poultry, meat, dairy products, and eggs, while increasing fish intake for 6 wk. Participants were assessed 1 wk before (W0) and 1 (W1) and 6 (W6) weeks after the diet change.

Results: By W6, fasting plasma long-chain ω-3 polyunsaturated fatty acids (ω-3 LC-PUFAs); docosahexaenoic (DHA) and eicosapentaenoic (EPA) had increased (+67% and +73%, respectively; P ≤ 0.001), with early rise of DHA (+22%), but not EPA at W1.The ω-3 index (sum of DHA and EPA as a percent of total fatty acids) increased from 2.1% to 3.4%. ARA decreased progressively (W1, -9%; W6, -16%; P < 0.001). ARA precursors γ-linolenic and dihomo-γ-linolenic acids also decreased, without changes in the ARA-derived mediators prostaglandin-E2 and leukotriene-B4. Myristic acid decreased at W1 (-37%) and W6 (-40%). There was no consistent change in SCD indices. At W6, systolic and diastolic blood pressure had declined by 8 and 5 mm Hg, respectively (P ≤ 0.013).

Conclusions: Shifting to a plant- and fish-based diet produces rapid and sustained increases in ω-3 LC-PUFAs and decreases the ω-6 PUFA ARA and its precursors, consistent with a cardio-protective profile. The rapid response suggests that these biomarkers may be useful for assessment of diet interventions.