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In the largest study of its
kind, researchers found lower average heart rates among healthy men who
regularly ate fish. The findings were reported in yesterday's rapid access issue
of Circulation: Journal of the American Heart Association.
"Increased heart rate is
a risk factor for sudden death," says the study's lead author Jean
Dallongeville, M.D., Ph.D., of the department of epidemiology and public health
at the Institut Pasteur de Lille in France. "These findings are
particularly important because sudden death most often occurs in men without a
known history of coronary heart disease [CHD]."
Sudden death occurs when the
heart stops abruptly, a condition also known as cardiac arrest. Most cardiac
arrest occurs when electrical impulses in the heart become rapid and/or chaotic.
Omega 3 fatty acids may
prevent sudden death and fatal cardiovascular events by regulating the heartbeat
and preventing irregular rhythms associated with sudden death, he says.
Cold-water fish such as salmon, tuna and mackerel are good sources of omega 3
fatty acids.
During the past 10 years,
epidemiological studies have found an association between fish consumption and a
decreased risk of CHD deaths and sudden death in healthy men and in those with
known CHD. Short-term trials also found that fish oil supplements at a dose of
about 1 gram a day reduced heart rate, diminished extra heartbeats and
normalized heart rhythm in both healthy people and those at high risk of CHD.
This is the largest study to
look at fish consumption - rather than fish oil supplements - and heart rate in
healthy men, Dallongeville says.
Researchers studied 9,758 men,
ages 50 to 59, from Lille, France and Belfast, Ireland. They were all free of
coronary heart disease and had been recruited through the World Health
Organization's MONICA (Monitoring Trends and Determinants in Cardiovascular
Disease) centers. The men answered a survey about their diets, physical activity
levels and other lifestyle factors. Blood samples were used to determine
cholesterol and triglyceride levels. A subset of 407 men was tested to determine
their blood levels of the omega 3 fatty acids: eicosapentaenoic acid (EPA) and
docosahexaenoic acid (DHA).
The men were divided into
groups according to their fish intake: less than once per week (27.3 percent),
once per week (46.9 percent), twice per week (20.1 percent) and more than twice
per week (5.7 percent).
Adjusted heart rate ranged
from 67.5 beats per minute (bpm) in men who ate fish less than once a week to
65.6 bpm for those consuming fish more than twice a week.
"Given the high incidence
of sudden death in the population, even a small reduction in heart rate might
have a significant public health impact," Dallongeville says.
"Heart rate decreased in
a linear fashion across categories of fish consumption, even after adjusting for
age, location, education level, physical activity, smoking and alcohol
consumption," he says.
The researchers found an
association between heart rate and blood levels of DHA, but not EPA.
They found no difference in
fish consumption between men in the two countries. However, fish eaters were
more educated, more physically active, drank alcohol less, and were less often
smokers than non-fish eaters. Since the link between fish intake and heart rate
was consistent in both countries, Dallongeville says the link appears to be
independent of lifestyle factors.
Co-authors include: John Yarnell, M.D., Ph.D.; Pierre Ducimetière, Ph.D.; Dominique Arveiler, M.D., Ph.D.; Jean Ferrières, M.D., M.P.H.; Michèle Montaye, M.D.; Gérald Luc, M.D.; Aluns Evans, M.D., Ph.D.; Annie Bingham, Bernadette Hass, M.D.; Jean-Bernard Ruidavets, M.D., Ph.D.; and Philippe Amouyel, M.D., Ph.D. (American Heart Association 2003)