The heart health benefits of omega-3-rich fish oil may be linked to its ability to favorably influence the variability in heart rates, says a meta-analysis of 15 studies.
The heart health benefits of fish oil, and the omega-3 fatty acids it contains, are well-documented, being first reported in the early 1970s by Dr Jorn Dyerberg and his co-workers in The Lancet and The American Journal of Clinical Nutrition.
To date, the polyunsaturated fatty acids (PUFAs) have been linked to improvements in blood lipid levels, a reduced tendency of thrombosis, blood pressure and heart rate improvements, and improved vascular function.
Various mechanisms have been proposed to explain fish oil’s cardioprotective effect, with improvements in heart rate listed among these, according to the scientists behind the new meta-analysis.
While individual studies have been contradictory, pooling the data, as the scientists did for this new meta-analysis, appears to support the proposal that “enhancement of vagal tone may be an important mechanism underlying the antiarrhythmic and other clinical effects of fish oil”.
Scientists from the Chinese PLA General Hospital in Beijing and the Medical College of Nankai University in Tianjin report their results in the American Journal of Clinical Nutrition .
Positive steps forward
The research was welcomed by Harry Rice, PhD, VP of regulatory & scientific affairs for the Global Organization for EPA and DHA Omega-3s (GOED).
“Despite the widespread knowledge about the cardiovascular benefits associated with Omega-3s, EPA and DHA, their mechanism(s) of action remain elusive,” he told us.
“This meta-analysis provides further insight into the benefits of omega-3s on heart rate, but it leaves many questions unanswered. In science, many times it's two steps forward, one step back. The net-net is positive!”
The Chinese scientists pooled data from 15 randomized controlled trials of fish oil on heart rate variability.
The results showed that heart rate variability was significantly improved following fish oil supplementation.
“The exact mechanisms by which fish oil (EPA and/or DHA) can affect the heart rate variability indexes and vagal function are currently unknown,” wrote the researchers.
“However, it has been indicated that fish oil (especially DHA) is abundant in nerve tissues and may play an important role in the maintenance of normal neurologic function. Furthermore, fish oil seemed to be helpful in the treatment of some neural degenerative diseases, such as Alzheimer disease.
“Future studies are needed to determine whether fish oil can directly influence nerve function in addition to its direct effect on cardiac electrophysiology.”
Source: American Journal of Clinical Nutrition
Published online March 20, 2013. doi: 10.3945/ajcn.112.049833
“Short-term effects of fish-oil supplementation on heart rate variability in humans: a meta-analysis of randomized controlled trials”
Authors: W. Xin, W. Wei, X-Y. Li