You might want to consider reading these if you are supplementing with fish oil or you are considering supplementing with fish oil.
The first of these is a list of quotation (with sources) calling into question the benefits of fish oil and citing the possible dangers:
“Fifty years ago, it was found that a large amount of cod liver oil in dogs’ diet increased their death rate from cancer by 20 times, from the usual 5% to 100%. A diet rich in fish oil causes intense production of toxic lipid peroxides, and has been observed to reduce a man’s sperm count to zero. [H. Sinclair, Prog. Lipid Res. 25, 667, 1989.]”
Next is an article written by biochemist Ray Peat on fish oil:
In 2004, a study of 29,133 men reported that the use of omega-3 oil or consumption of fish didn’t decrease depression or suicide, and in 2001, a study of 42,612 men and women reported that after more than 9 years the use of cod liver oil showed no protective effect against coronary heart disease (Hakkarainen, et al., 2004; Egeland, et al., 2001).
<<The most popular way of arguing that fish oil will prevent heart disease is to show that it lowers blood lipids, continuing the old approach of the American Heart Association’s “heart protective diet.” Unfortunately for that argument, it’s now known that the triglycerides in the blood are decreased because of the fish oil’s toxic effects on the liver (Hagve and Christophersen, 1988; Ritskes-Hoitinga, et al., 1998). In experiments with rats, EPA and DHA lowered blood lipids only when given to rats that had been fed, in which case the fats were incorporated into tissues, and suppressed mitochondrial respiration (Osmundsen, et al., 1998).>>