The new study may help explain why. ''We've shown an entirely new effect of omega-3 fatty acids, which may be to slow down the biological aging process in patients with coronary heart disease," says lead author Ramin Farzaneh-Far, MD, an assistant professor of medicine at the University of California San Francisco.
Farzaneh-Far and his colleagues looked at a marker of biological age -- the rate of shortening of telomeres, structures at the end of a chromosome involved in its replication and stability. As the telomeres shorten over time, the eventual result is cell death, scientists believe.
In previous research, Farzaneh-Far says, his team looked at the same group of heart disease patients and found that telomere length was ''a powerful predictor of death and bad outcomes [from heart disease]. In that [study], we found the shorter your telomeres, the greater your risk of death."
In the new study, the higher the blood levels of omega-3 fatty acids in the patients evaluated, the slower the rate of telomere shortening.
"We looked at the biological effects of higher blood levels," Farzaneh-Far tells WebMD, "not supplement intake."
The study is published in the Journal of the American Medical Association.
Omega-3s and Aging Study Details
For the study, the researchers evaluated 608 patients with stable heart disease, recruited from the Heart and Soul Study from September 2000 and December 2002, following them up for a median of six years (half were followed more, half less).
Participants gave blood samples at the beginning of the study, which were evaluated for omega-3 fatty acid levels. The researchers also isolated DNA from the blood and evaluated the length of the telomere of the leukocyte, a type of blood cell.
Over the follow-up period, "patients with the lowest blood levels of omega-3 fatty acids exhibited a rate of telomere shortening 2.6 times faster than patients with the highest levels of omega-3 fatty acids," Farzaneh-Far tells WebMD.
How does that relate to aging? "We don’t have enough data to be able to convert the changes of telomere shortening into years of aging," he says. "This may be one of the first studies to look at the change in telomere length over time."
There was no association found between omega-3 fatty acid levels and telomere length at the study start. The researchers aren't sure why, but state that omega-3 fatty acid levels is one of many influences on the length of the telomeres, with other factors including inflammation in the body, obesity, oxidative stress, and lack of physical activity.
Would high omega-3 blood levels help those without heart disease? Farzaneh-Far can't say. ''Whether this effect of omega-3 fatty acids on telomere length is present in those without coronary heart disease, I just can't say," Farzaneh-Far says, noting it was beyond the scope of the study. However, he adds, ''it could be.'' Telomere shortening occurs in everyone, he says.
Omega-3 Fatty Acids & Aging: Other Opinions
''This is very exciting news, to show how fish oil works on a cellular level," says Ravi Dave, MD, a cardiologist at Santa Monica-UCLA Medical Center & Orthopaedic Hospital and an associate professor of medicine at the University of California Los Angeles David Geffen School of Medicine.
The new finding, he tells WebMD, builds on previous research. "There has been a strong association found that if you take marine omega-3 fatty acids, it reduces the risk of cardiovascular disease."
Researchers have been trying to pin down why. Several proposed mechanisms have been found, including reduction of inflammation in the body or reducing the risk of abnormal heart rhythms, Dave says.
With the new finding, he says, "it's no longer a hypothesized mechanism. It has some basis behind how it works."
But, he adds, "fish oils are only one of the things that affect telomere length." Many other factors, he says, such as oxidative stress on the cells, play a role.
Eventually, Dave says, if the telomere research bears out, a test to check a person's telomere length may be one way to predict the risk of heart disease.
The new research demonstrates a protective effect of fish oil on the aging clock, adds Robert Zee, PhD, assistant professor of medicine at Harvard Medical School and director of molecular epidemiology at the division of preventive medicine of Brigham & Women's Hospital in Boston. He has reported a link between shorter telomere length and heart attacks. But the new findings need replication, he says.
Omega-3s and Health: Advice
What should healthy people and those with heart disease do in terms of omega-3s?
Farzaneh-Far points to the existing American Heart Association guidelines. "The American Heart Association already recommends at least a gram a day" of omega-3 fatty acid intake for those with documented heart disease, he says. Preferably it should come from oily fish such as salmon, mackerel, or albacore tuna, according to the AHA, but supplements could be considered if a patient's doctor agrees.
For those who don't have heart disease, the AHA recommends eating a variety of fish, preferably oily types such as salmon, at least twice a week, and including in the diet healthy oils such as flaxseed, canola, and soybean.
One of the researchers, William S. Harris of the University of South Dakota, reports receiving research grants from companies with interests in omega-3 fatty acids. Another co-author, Elizabeth H. Blackburn, PhD, shared the 2009 Nobel Prize in Physiology or Medicine for the discovery of how chromosomes are protected by telomeres and the enzyme telomerase.