To investigate the effects of alpha-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.
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).
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.
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.