The letters from Dr Kinrys and Drs Su et al regarding the possible mood-elevating effects of ω3 fatty acids and the issue of the proper placebo for ω3 fatty acid studies are crucial and timely issues.
The choice of the most appropriate placebo is an important and surprisingly difficult problem in ω3 fatty acid research. Most fish-oil preparations are produced in room temperature air, which leads to some oxidation (degradation) of the ω3 fatty acids. Oxidized fish oil is rancid and has a foul odor and taste, and masking the fishy taste, even with a citrus oil, can be difficult when using an unconcentrated and lower-quality fish oil preparation. Highly concentrated fish oil is now commercially available and is generally prepared by a low-temperature vacuum distillation process, which separates the ω3 fatty acids from most of the fishy-tasting substances (as well as pollutants). In addition, processing and encapsulating the fish oil in a nitrogen atmosphere can prevent oxidation of the fragile ω3 chemical structure and further reduce any fishy odor and taste.
Stoll AL, Damico KE, Marangell LB, Severus WE. Are ω3 Fatty Acids Beneficial in Depression but Not Mania?. Arch Gen Psychiatry. 2000;57(7):716-717. doi: