People who took cod liver oil every day were 34% less likely to be depressed than were those who had not, according to a new study. Researchers examined the diets of 21,835 Norwegian participants aged 40 to 49 and 70 to 79. They found that 2.5% of those who used cod liver oil every day had high levels of depression compared to 3.8% of those who did not use cod liver oil. Doctors considered other factors that might contribute to depression including age, gender, smoking, consuming coffee or alcohol, physical activity and education. Scientists noted that in the 40 to 49 year old group, those who had taken cod liver oil the longest were least likely to be depressed. The doctors recommend taking 500 mg of cod liver oil per day.