The benefits of omega-3 fatty acids for cardiovascular health are well-known, as the American Heart Association recommends eating at least two servings of fish a week.
However, exactly how fatty fish aids heart health has been largely a mystery. New research suggests one way omega-3s may help is by counteracting the detrimental effects of mental stress on the heart.
A new study finds that volunteers who took fish oil supplements for several weeks had a blunted response to mental stress in several measurements of cardiovascular health.
Specifically, participants who took the fish oil supplements presented lower heart rates and muscle sympathetic nerve activity (MSNA) — part of the “fight or flight” response — compared to volunteers who took olive oil instead.
Researchers believe the results may explain why taking fish oil could be beneficial to the heart and might eventually help doctors prevent heart disease in select populations.
In the study, Carter and his colleagues worked with 67 adult volunteers. At the beginning of the study, each volunteer underwent a battery of tests to assess cardiovascular function, including heart rate, blood pressure, MSNA, and blood flow through the forearm and calf.
These tests were performed first when the volunteers were at rest, and then again while they were performing a mental arithmetic test while the investigator encouraged them to hurry, a situation designed to induce acute mental stress.
The study subjects were then nearly equally assigned to take either 9 grams of fish oil per day or 9 grams of olive oil, a placebo that hasn’t been shown to have the same beneficial cardiovascular effects as fish oil.
None of the volunteers were aware of which supplement they were taking. After 8 weeks of this intervention, the study subjects underwent the same tests again.
Investigators discovered test results didn’t change between the two groups of study subjects when they were at rest. But results for the volunteers who took fish oil and those who received the placebo differed significantly for some of the tests during the mental stress.
Those in the fish oil group showed blunted heart rate reactivity while they were stressed compared to those who took olive oil. Similarly, the total MSNA reactivity to mental stress was also blunted in the fish oil group.
Researchers say that future studies might focus on the effects of taking fish oil for longer time periods and examining this effect on older populations or people with cardiovascular disease.
“Overall,” the study authors say, “the data support and extend the growing evidence that fish oil may have positive health benefits regarding neural cardiovascular control in humans and suggest important physiological interactions between fish oil and psychological stress that may contribute to disease etiology.”
The study appears in the American Journal of Physiology.
Source: American Physiological Society