Jason Carter, chairman of the Department of Kinesiology and Integrative Physiology at Michigan Technological University, conducted the study, which involved 67 healthy volunteer test participants in their 20s. Over a two-month period, they were given either 9 grams of fish body oil pills or 9 grams of olive oil as a placebo.
The test subjects were screened for heart rate, blood pressure and other related health information. At the end of the study period, both groups took a mental arithmetic test that involved adding and subtracting numbers in their head. Their stress response was measured at that time.
"Those in the fish oil group showed blunted heart rate reactivity while they were stressed compared to those who took olive oil," Carter said in a statement.
"Similarly, the total muscle sympathetic nerve activity reactivity to mental stress was also blunted in the fish oil group."
However, there was not much difference between the two groups at rest, Carter said.
The study was published in the American Journal of Physiology -- Regulatory, Integrative and Comparative Physiology, published by the American Physiological Society.