The effect of dietary supplementation with different amounts of a fungal oil containing arachidonic acid (AA, 20:4n--6) and a microalgal oil containing docosahexaenoic acid (DHA, 22:6n--3), blended to give a ratio of AA to DHA of 1.25:1.00, on plasma lipid AA, DHA, cholesterol, and triacylglycerols was evaluated in healthy men. Subjects (n = 8/group) were given 28.8 g fat/d containing 0 x (0 g AA, 0 g DHA), or 1 x (0.8 g AA, 0.6 g DHA), 3 x (2.2 g AA, 1.7 g DHA), or 5 x (3.6 g AA, 2.9 g DHA) the estimated intake of infants fed human milk with 0.5% AA and 0.4% DHA for 14 d. No clinically significant dose-related effects were seen on physical examination or from routine laboratory tests. The microalgal-fungal oil blend resulted in a significant, dose-dependent increase in plasma cholesterol and percentage phospholipid AA and DHA, and a decrease in percentage triacylglycerols and phospholipid linoleic acid. Plasma phospholipid AA and DHA increased approximately 18% and 50%, respectively, with the 1 x dose, similar to that expected at intakes provided by human milk. These oils appear to be safe dietary sources of AA and DHA for healthy adults at intakes equivalent to 0.8 g AA and 0.6 g DHA/d for > or = 2 wk.