Study of Older Men Challenges Heart Association
Recommendation of Eating Fish Twice Weekly
Study finds eating fatty fish once a week reduces
heart failure risk, eating more does not. Omega-3 fatty acid benefits
confirmed, too if taken in the right amounts
April 22, 2009 A study involving almost 40,000
older men has found that eating salmon or other fatty fish just once a
week lowers a mans risk of heart failure by 12 percent, although the
American Heart Association recommends eating fish twice a week. But, to
really maximize the benefits of consuming omega-3 fatty acids a man
needs 36 grams per day, which lowers his heart failure risk by 33
percent. Mysteriously, the men who consumed fish more often, including
twice a week, and those who consumed more omega-3 had no reduction in
heart failure rates.
(American Heart Association recommendations below
news report.)
This large study, which adds to growing evidence
that omega-3 fatty acids are of benefit to cardiac health, was led by
researchers at Beth Israel Deaconess Medical Center (BIDMC) and reported
in today's on-line issue of the European Heart Journal.
"Previous research has demonstrated that fatty fish
and omega-3 fatty acids help to combat risk factors for a range of
heart-related conditions, such as lowering triglycerides [fats in the
blood] reducing blood pressure, heart rate and heart rate variability,"
explains first author Emily Levitan, PhD, a research fellow in the
Cardiovascular Epidemiology Research Center at BIDMC.
"Collectively, this may explain the association
with the reduced risk of heart failure found in our study."
A life-threatening condition that develops when the
heart can no longer pump enough blood to meet the body's needs, heart
failure (also known as congestive heart failure) is usually caused by
existing cardiac conditions, including high blood pressure and coronary
artery disease. Heart failure is the leading cause of hospitalization
among patients 65 and older, and is characterized by such symptoms as
fatigue and weakness, difficulty walking, rapid or irregular heartbeat,
and persistent cough or wheezing.
The researchers followed 39,367 Swedish men between
the ages of 45 and 79 from 1998 to 2004. The researchers recorded
details of the men's diet and tracked the men's outcome through Swedish
inpatient hospital registers and cause-of-death registers.
During this period, 597 men in the study (with no
previous history of heart disease or diabetes) developed heart failure.
Thirty-four men died.
Analysis of their numbers showed that the men who
ate fatty fish (herring, mackerel, salmon, whitefish and char) once a
week were 12 percent less likely to develop heart failure, compared with
men who ate no fatty fish.
Although this association did not reach statistical
significance, notes Levitan, the researchers also found a statistically
significant association with the intake of marine omega-3 fatty acids,
which are found in cod liver and other fish oils:
The men who consumed approximately 0.36 grams a day
were 33 percent less likely to develop heart failure than the men who
consumed little or no marine omega-3 fatty acids.
"We divided the men into five groups based on their
intake of fatty fish," explains Levitan.
"The first group consumed little or no fatty fish;
at the other end of the spectrum, the fifth group consumed significant
quantitities - three or more servings per week.
We found that while the 'middle group' who ate
one serving per week had a 12 percent reduced risk of heart failure,
the next two groups, who ate either two servings a week or three or more
servings a week, had nearly the same heart failure risk as the men who
ate no fish at all."
The findings were similar when the researchers
looked at fish oil consumption:
Among five groups based on fish oil consumption,
the middle group, who consumed 0.36 grams per day of omega-3 fatty acids
showed a 33 percent reduced risk of heart failure, while the men who
consumer greater quantities (approximately 0.46 grams per day or 0.71
grams per day) had a risk of heart failure similar to the men who
consumed little or no fish oils.
"The higher rates of heart failure in men who
consumed the most fatty fish or marine omega-3 fatty acids compared with
the men who had moderate consumption may be due to chance," explains
Levitan.
Alternatively, she explains, the men who ate more
fish may already be in poor health, and may be trying to improve their
health through fish consumption.
"Our study reinforces the current recommendations
for moderate consumption of fatty fish," notes Levitan. "Current
guidelines from the American Heart Association recommend eating fatty
fish twice a week. It will be important, going forward, to replicate
these findings in other populations, particularly those including women,
as our study looked at men only."
Background information:
Study coauthors include senior author Murray
Mittleman of BIDMC's Cardiovascular Epidemiology Research Unit and
Alicja Wolk of the Karolinska Institute, Sweden.
This study was supported, in part, by grants from
the Swedish Foundation for International Cooperation in Research and
Higher Education; and the National Heart, Lung and Blood Institute,
National Institutes of Health.
Beth Israel Deaconess Medical Center is a patient
care, teaching and research affiliate of Harvard Medical School and
consistently ranks in the top four in National Institutes of Health
funding among independent hospitals nationwide. BIDMC is a clinical
partner of the Joslin Diabetes Center and is a research partner of the
Dana-Farber/Harvard Cancer Center. BIDMC is the official hospital of the
Boston Red Sox.
Fish and Omega-3
Fatty Acids
American Heart Association Recommendation
Omega-3 fatty acids benefit the heart of healthy
people, and those at high risk of or who have cardiovascular
disease.
We recommend eating fish (particularly fatty fish)
at least two times a week. Fish is a good source of protein and doesnt
have the high saturated fat that fatty meat products do. Fatty fish
like mackerel, lake trout, herring, sardines, albacore tuna and salmon
are high in two kinds of omega-3 fatty acids, eicosapentaenoic acid
(EPA) and docosahexaenoic acid (DHA).
To learn about omega-3 levels for different types
of fish as well as mercury levels, which can be a concern see our
Encyclopedia entry on Fish, Levels of Mercury and Omega-3 Fatty Acids.
We also recommend eating tofu and other forms of
soybeans, canola, walnut and flaxseed, and their oils. These contain
alpha-linolenic acid (LNA), which can become omega-3 fatty acid in the
body. The extent of this modification is modest and controversial,
however. More studies are needed to show a cause-and-effect relationship
between alpha-linolenic acid and heart disease.
The table below is a good guide to use for
consuming omega-3 fatty acids.
Summary of Recommendations for Omega-3 Fatty Acid
Intake
Population
Recommendation
Patients without documented coronary heart disease (CHD)
Eat a variety of (preferably fatty) fish at least
twice a week. Include oils and foods rich in alpha-linolenic
acid (flaxseed, canola and soybean oils; flaxseed and
walnuts).
Patients with documented CHD
Consume about 1 g of EPA+DHA per day, preferably
from fatty fish. EPA+DHA in capsule form could be
considered in consultation with the physician.
Patients who need to lower triglycerides
2 to 4 grams of EPA+DHA per day provided as capsules
under a physicians care.
Patients taking more than
3 grams of omega-3 fatty acids from capsules should do so only under a
physicians care. High intakes could cause excessive bleeding in some
people.
Background
In 2002, the American Heart Association released a
scientific statement, Fish
Consumption, Fish Oil, Omega-3 Fatty Acids and Cardiovascular Disease, on the
effects of omega-3 fatty acids on heart function (including
antiarrhythmic effects), hemodynamics (cardiac mechanics) and arterial
endothelial function. The link between omega-3 fatty acids and CVD risk
reduction are still being studied, but research has shown that omega-3
fatty acids
● decrease risk of arrhythmias, which can lead
to sudden cardiac death
● decrease triglyceride levels
● decrease growth rate of atherosclerotic plaque
● lower blood pressure (slightly)
What do epidemiological and observational
studies show?
Epidemiologic and clinical trials have shown that
omega-3 fatty acids reduce CVD incidence. Large-scale epidemiologic
studies suggest that people at risk for coronary heart disease benefit
from consuming omega-3 fatty acids from plants and marine sources.
The ideal amount to take isnt clear. Evidence
from prospective secondary prevention studies suggests that taking
EPA+DHA ranging from 0.5 to 1.8 grams per day (either as fatty fish or
supplements) significantly reduces deaths from heart disease and all
causes. For alpha-linolenic acid, a total intake of 1.53 grams per day
seems beneficial.
Randomized clinical trials have shown that omega-3
fatty acid supplements can reduce cardiovascular events (death,
non-fatal heart attacks, non-fatal strokes). They can also slow the
progression of atherosclerosis in coronary patients. However, more
studies are needed to confirm and further define the health benefits of
omega-3 fatty acid supplements for preventing a first or subsequent
cardiovascular event. For example, placebo-controlled, double-blind,
randomized clinical trials are needed to document the safety and
efficacy of omega-3 fatty acid supplements in high-risk patients (those
with type 2 diabetes, dyslipidemia, hypertension and smokers) and
coronary patients on drug therapy. Mechanistic studies on their
apparent effects on sudden death also are needed.
Increasing omega-3 fatty acid intake through foods
is preferable. However, coronary artery disease patients may not be
able to get enough omega-3 by diet alone. These people may want to talk
to their doctor about taking a supplement. Supplements also could help
people with high triglycerides, who need even larger doses. The
availability of high-quality omega-3 fatty acid supplements, free of
contaminants, is an important prerequisite to their use.
>> To find this report and read the latest
recommendation from the American Heart Association,
Click Here
Fish, Levels of
Mercury and Omega-3 Fatty Acids
Fish is a good source of protein and, unlike fatty
meat products, its not high in saturated fat. Its also a good source
of omega-3 fatty acids, which benefit heart health.
The American Heart Association recommends eating
fish at least twice a week. However, some types of fish may contain high
levels of mercury, PCBs (polychlorinated biphenyls), dioxins and other
environmental contaminants. Levels of these substances are generally
highest in older, larger, predatory fish and marine mammals. Levels of
mercury and omega-3 fatty acids for various fish and shellfish are shown
below.
Top 10 fish and shellfish consumed in the United
States
Mean mercury
level in parts per million (ppm)
Omega-3
fatty acids
(grams per 3-oz. serving)
Canned tuna
(light)
0.12
0.170.24
Shrimp
ND*
0.29
Pollock
0.06
0.45
Salmon (fresh,frozen)
0.01
1.11.9
Cod
0.11
0.150.24
Catfish
0.05
0.220.3
Clams
ND*
0.25
Flounder or
sole
0.05
0.48
Crabs
0.06
0.270.40
Scallops
0.05
0.180.34
Other common seafoods
Mean
mercury level in
parts per million (ppm)
Omega-3
fatty acids
(grams per 3-oz. serving)
Lobster
0.31
0.070.46
Grouper
0.55
0.23
Halibut
0.26
0.601.12
Oysters
ND*
0.371.14
Mahi mahi
0.19
0.13
Herring
0.04
1.92.0
>> Read more on this topic at the American Heart
Association,
Click Here
Keep up with the latest news for senior citizens, baby
boomers
April 22, 2009 A study involving almost 40,000
older men has found that eating salmon or other fatty fish just once a
week lowers a mans risk of heart failure by 12 percent, although the
American Heart Association recommends eating fish twice a week. But, to
really maximize the benefits of consuming omega-3 fatty acids a man
needs 36 grams per day, which lowers his heart failure risk by 33
percent. Mysteriously, the men who consumed fish more often, including
twice a week, and those who consumed more omega-3 had no reduction in
heart failure rates.