Tinned tuna lowers the risk of an irregular hearbeat

Jul 19 2004

A new study out today suggests that tuna or broiled/baked fish lowers the risk of an irregular hearbeat among elderly people.

The study is published in today's issue of Circulation: Journal of the American Heart Association.

Dariush Mozaffarian, lead author of the study said, "The results suggest that regular intake of tuna or other broiled or baked fish may be a simple and important deterrent to atrial fibrillation among older men and women."

Atrial fibrillation is the most common heart rhythm disorder in the U.S., affecting more than 2 million adults. The prevalence of the condition is rising and scientists predict that about 5.6 million Americans will have the disorder by 2050. Known causes of AF include abnormalities in the heart’s structure and long-term uncontrolled high blood pressure.

Atrial fibrillation occurs when electrical signals in the heart's upper chambers (the atria) are fired in a very fast, uncontrolled manner. Electrical signals then arrive in the heart's lower chambers (the ventricles) in an erratic pattern, creating an irregular heartbeat and affecting the heart’s ability to pump blood. Atrial fibrillation can produce symptoms including palpitations, an unexplained, rapid heartbeat, lightheadedness, or occasionally chest pain. It can also be asymptomatic. Atrial fibrillation can lead to complications such as stroke and congestive heart failure. Treatment via drugs, surgery or devices, is designed to slow the heart rate and/or restore normal rhythm, and to prevent stroke. Blood-thinning medications (anticoagulants) are an important means of preventing stroke in Atrial fibrillation patients.

The incidence of atrial fibrillation increases with age, rising to approximately 2 percent per year after age 65. Researchers analyzed data from the National Heart, Lung, and Blood Institute-funded Cardiovascular Health Study, a prospective, population-based, multicenter study on 4,815 people over age 65 whose usual dietary intake was assessed in 1989–90. During 12 years of follow-up, doctors diagnosed 980 cases of AF.

The researchers found that higher consumption of tuna fish (fresh or canned) or other fish that was broiled or baked was associated with lower incidence of atrial fibrillation.

It was also noted that people who consumed fish one to four times per week had a 28 percent lower risk of atrial fibrillation, while those who had five or more servings had a 31 percent lower risk compared to those who ate fish less than once a month.

The research team also found that eating fried fish or fish burgers was not associated with lower risk of atrial fibrillation.

Dariush Mozaffarian, M.D., M.P.H is an instructor of medicine and researcher in the Channing Laboratory, Brigham and Women's Hospital and Harvard Medical School in Boston.

Tuna are several species of ocean-dwelling fish in the family Scombridae. Tuna are fast swimmers and like most other fish species are cold-blooded. Unlike most ocean fish species, which have white flesh, the flesh of tuna is pink. This is because the tuna's blood has a higher oxygen carrying ability than other fish species. Some of the larger tuna species such as the bluefin tuna can raise their blood temperature above the water temperature with muscular activity. Though not really warm-blooded, this enables them to live in cooler waters and survive a wider range of circumstances.