Effects of Dietary α-Linolenic Acid, Eicosapentaenoic Acid or Docosahexaenoic Acid on Parameters of Glucose Metabolism in Healthy Volunteers

Abstract

Aim: To investigate the effects of α-linolenic acid (ALA) and purified eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) on fasting concentrations of glucose, insulin, fructosamine, on glycosylated haemoglobin (HbA1c) and on insulin sensitivity. Methods: A randomized strictly controlled dietary study in 48 healthy volunteers (13 males, 35 females) of normal body weight (mean age 25.9 years) with three dietary groups (ALA, EPA and DHA) and a parallel design, consisting of two consecutive periods. Subjects received a 2-week wash-in diet rich in monounsaturated fatty acids followed by experimental diets enriched with equal amounts of ALA, EPA, or DHA for 3 weeks. Mean dietary intake of ALA in the ALA group was 6.0 g/day (2.5% of energy intake), mean intake of EPA in the EPA group was 2.8 g/day (1.1% of energy intake) and mean intake of DHA in the DHA group was 2.9 g/day (1.1% of energy intake). Results: Fasting serum concentrations of insulin and fructosamine and of HbA1c did not change significantly after consuming the ALA, EPA or DHA diet. Fasting serum glucose levels did not change significantly following either the ALA or DHA diet. During the EPA diet, fasting glucose concentration slightly increased by 0.15 mmol/l (p < 0.05). All measured values of all subjects were in the reference ranges for healthy adults. No effects on insulin sensitivity indicated by the HOMA insulin resistance index could be observed. Conclusions: Except for the minor effect of EPA on fasting glucose levels, the moderate amounts of dietary ALA, EPA or DHA administered in this study did not significantly affect blood concentrations of glucose, insulin, fructosamine and HbA1c in healthy normal-weight men and women over a time course of 3 weeks.

Effects on metabolic markers are modified by PPARG2 and COX2 polymorphisms in infants randomized to fish oil

“…That FO supplementation only seems to exert an effect on plasma glucose among PPARG2 heterozygotes may explain why previous studies in humans have been unable to show an effect of FO on glucose homeostasis and insulin resistance. We found no effect of FO on glucose homeostasis and HOMA, which is in line with findings by Pedersen et al (2010) in teenage boys and findings from studies in adults (Egert et al 2008;Giacco et al 2007). In contrast, other studies in adults have observed improved insulin sensitivity as a consequence of fish intake or FO supplementation (Abete et al 2008;Ramel et al 2008).…”

Higher dietary intake of alpha-linolenic acid is associated with lower insulin resistance in middle-aged Japanese

“…Although animal studies are also in line with our finding (Ghafoorunissa et al, 2005;Chicco et al, 2009), some human studies reported either no effect (Finnegan et al, 2003;Egert et al, 2008) or the opposite (Hodge et al, 2007). Some studies have stratified their population by the level of obesity, and reported that total PUFA intake was inversely associated with IR or DM incidence only in subjects with a lower degree of obesity (Colditz et al, 1992;Mayer-Davis et al, 1997;Salmeron et al, 2001).…”

“…The associations of ALA, an inefficient precursor of EPA and DHA in humans (Burdge, 2006), also remain unclear (Barre, 2007). For example, intervention studies failed to find associations between dietary ALA and fasting glucose or insulin concentrations (Finnegan et al, 2003;Egert et al, 2008). While ALA content in adipose tissue or plasma phospholipid was inversely associated with glucose intolerance (Carlson and Walldius, 1975) or DM incidence (Wang et al, 2003), a cohort study found that a high ALA intake was significantly associated with increased DM incidence (Hodge et al, 2007).…”

Eicosapentaenoic acid improves insulin sensitivity and blood sugar in overweight type 2 diabetes mellitus patients: a double-blind randomised clinical trial

“…Egert et al reported no change in the HbA1c level of individuals who consumed 2.8 g of EPA a day for three weeks. (19) Another study, in which patients consumed 500 mg of EPA a day with or without vitamin C for eight weeks, showed that EPA consumption could reduce HbA1c conspicuously. (20) From these studies, it seems that the duration of intervention plays a key role in the changes in HbA1c levels, since the lifespan of red blood cells is almost 120 days.…”