The influence of different combinations of γ-linolenic acid, stearidonic acid and EPA on immune function in healthy young male subjects

Abstract

To determine the effects of EPA, stearidonic acid (STA) or g-linolenic acid (GLA) on immune outcomes, healthy male subjects consumed one of seven oil blends for 12 weeks. EPA consumption increased the EPA content of peripheral blood mononuclear cells (PBMC). Consumption of GLA (2·0 g/d) in the absence of STA or EPA increased di-homo-GLA content in PBMC. Neither STA nor its derivative 20 : 4n-3 appeared in PBMC when STA (, 1·0 g/d) was consumed. However, STA (1·0 g/d), in combination with GLA (0·9 g/d), increased the proportion of EPA in PBMC. None of the treatments altered neutrophil or monocyte phagocytosis or respiratory burst, production of inflammatory cytokines by monocytes, T lymphocyte proliferation or the delayed-type hypersensitivity response. Production of cytokines by T lymphocytes increased in all groups, with no differences among them. The proportion of lymphocytes that were natural killer cells decreased significantly in subjects receiving 2·0 g EPA or GLA/d. There were no other effects on lymphocyte sub-populations. Plasma IgE concentration decreased in most groups, but not in the control group. Plasma IgG 2 concentration increased in the EPA group. Thus, EPA or GLA at a dose of 2·0 g/d have little effect on key functions of neutrophils, monocytes and T lymphocytes, although at this dose these fatty acids decrease the number of natural killer cells. At this dose EPA increases IgG 2 concentrations. STA can increase immune cell EPA status, but at 1·0 g/d does not affect human immune function.

Metabolism and functional effects of plant-derived omega-3 fatty acids in humans

“…In studies where humans have increased their intake of SDA through supplementation, incorporation of SDA itself into blood lipids and cells has been very small but significant increases in EPA have been reported [97][98][99]. For example, Harris et al demonstrated that SDA modifies the ω-3 index (EPA+DHA in RBCs) with greater efficiency than ALA [103].…”

“…As explained above, the biosynthesis of longerchain ω-3 PUFAs from SDA is considered to be more efficient than from ALA due to it not requiring the rate limiting step catalysed by D6D and studies which have directly compared consumption of SDA to that of ALA have shown a greater increase of EPA in blood lipids and cells than seen for ALA consuming subjects, although no significant changes in plasma or red blood cell (RBC) DHA levels were observed [97][98][99][100].…”

“…Other studies comparing the effects of SDA, ALA or EPA supplementation on the increase in blood and blood cell VLC ω-3 PUFAs report that EPA supplementation resulted in higher EPA levels than SDA supplementation, which in turn was higher than ALA supplementation. However, neither ALA, nor SDA, nor EPA resulted in higher DHA levels [97][98][99][100].…”

“…Increased consumption of ALA or SDA has been shown to increase the proportion of EPA and DPA in membranes of inflammatory cells such as neutrophils, monocytes and lymphocytes [38,99,107,128,130,133,[152][153][154]163] (Tables 7 and 8), indicating the potential of plant derived ω-3 PUFAs to reduce inflammation and to protect against chronic inflammatory diseases.…”

“…Studies which directly compared the effects of SDA with ALA or EPA supplementation on the concentrations of in EPA, DPA and DHA in humans reported that SDA resulted in higher plasma and cell EPA than ALA [97][98][99][100] (Table 8). None of these studies reported an increase in DHA concentrations after an increase in SDA intake, which is consistent with findings following increased intakes of ALA.…”