April 22, 2009 -- Eating moderate amounts of omega-3-rich fatty fish may help protect against heart failure, according to a newly published study from Boston’s Harvard Medical School and Sweden’s Karolinska Institute.
But the research also suggests that too much of a good thing might not be so good for the heart.
Swedish men in the study who ate moderate amounts of fatty fish were found to have a lower risk of heart failure than men who ate no fish.
They also had a lower heart failure risk than men who ate a lot more fish than they did.
Fatty fish like salmon, tuna, mackerel, herring, and sardines are considered the best food sources of omega-3 fatty acids, dietary fats that have been shown in study after study to protect against heart disease and death from heart attack or stroke.
But the new research is among the first to suggest that the benefits extend to heart failure, characterized by an inability of the heart to pump adequate oxygen-rich blood to the body’s other organs.
Heart failure is one of the biggest causes of hospitalization and death among the elderly.
Omega-3 and Heart Failure
Researchers followed almost 40,000 men between the ages of 45 and 79 for six years, from 1998 until 2004.
All of the men were participants in a larger Swedish health study, and all of them completed detailed questionnaires designed to determine how often they ate a wide range of foods.
None of the participants had established cardiovascular disease or diabetes when they entered the study, but 597 were diagnosed with heart failure and 34 died from the condition over the six-year observation period.
The men were divided into five groups depending on their intake of fatty fish, with the group on the low end of the spectrum eating no fish and those on the high end eating fish three or more times a week.
The researchers report that:
- The group in the middle of the spectrum, which averaged one serving of fish a week, had a 12% reduction in heart failure risk.
- The groups that ate no fish and the most fish had similar risks of heart failure.
- Study participants who got the equivalent of 0.36 grams of omega-3 a day from fish had a 33% reduction in heart failure risk.
- Taking omega-3 supplements was not associated with an increase or decrease in risk, but very few men in the study (less than 5%) took omega-3 supplements (such as fish oil).
Lead researcher Emily Levitan, ScD, a research fellow at Beth Israel Deaconess Medical Center and Harvard Medical School, tells WebMD that it is not clear why the men who ate the most fish had a heart failure risk similar to the men who ate no fish.
She said the finding may be due to chance or to the fact that sicker people may improve their diets and eat more fish in an effort to improve their health.
Data From Other Studies
Harvard cardiologist Dariush Mozaffarian, MD, who was not involved with the latest study,
led the research team that conducted one of the only other studies examining omega-3 consumption and heart failure. His report, published in 2005, suggests that eating broiled or baked, but not fried, fish is associated with a lower risk of heart failure. But unlike the newly published study, frequent fish consumption (three or more times a week) appeared to be more protective than more moderate fish consumption.
Mozaffarian tells WebMD that his own, as yet unpublished, research suggests that people do tend to increase their consumption of fish after learning that they have risk factors for heart disease.
“The health benefits of fish are well known, so it makes sense that people who are already sick would eat more fish because they are worried about their health,” he says.
He says more research is needed to confirm that eating fatty fish helps protect against heart failure.
“Heart failure is a common disease of aging and it is the most common reason for hospitalizations among the elderly,” he says. “People with severe heart failure are in and out of the hospital and they have a very low quality of life. This study and our previous work suggest another important benefit for omega-3 and fish consumption that could have a big impact on public health.”