Fish and soy oil might help fight heart attacks

12/04/05 Taking daily supplements of fish or soy oil may improve cardiac function and protect against heart attacks in the short-term. Study results published in the April issue of CHEST, the peer-reviewed journal of the American College of Chest Physicians, are the first to show that soy oil increases heart rate variability (HRV), a measure of cardiac autonomic function.

"Our findings contradict the current belief in the medical community that increasing the intake of omega-3 fatty acids produces only long-term cardiac benefits," said the study's lead author, Fernando Holguin, MD, Emory University School of Medicine, Atlanta, GA.  "In fact, our study group showed improvements in heart function in as little as two weeks."

Researchers from Atlanta, GA, Boston, MA, and Cuernavaca, Mexico, took the HRV of 58 elderly patients every other day for two months to establish an HRV baseline for each participant.  For 11 weeks, half of the study participants took a daily 2 g supplement of fish oil, which contains marine-derived omega-3 fatty acids, and the other half took a daily 2 g supplement of soy oil, which contains plant-derived omega-3 fatty acids.  The omega-3 fatty acids improve heart function by providing greater variability between beats, therefore reducing the risk of arrhythmia and/or sudden death.  Heart rate variability is measured by high-frequency (HF) and low-frequency (LF) domain components and standard deviation of normal RR intervals (SDNN).  Those who received fish oil experienced a significant increase in total HF and LF domain components and SDNN.  Patients who received soy oil experienced a marginally significant increase in HF and LF domain components and a significant increase in SDNN.

"Reduced HRV predicts mortality and arrhythmic complications in patients who have had a heart attack, as well as those who are considered healthy," said Dr. Holguin.  "Taking a daily supplement of fish or soy oil may help reduce the risk of suffering an adverse cardiovascular event, such as arrhythmia or sudden death, specially in persons with known cardiovascular disease or at increased risk for it, such as those with lipid disorders, advanced age, hypertension, a history of smoking, and family history of heart disease."

Researchers also discovered that while patients in both groups experienced a significant increase in HRV, those who took the fish oil supplements achieved a greater increase in a shorter time period.  Patients who received fish oil experienced increased HRV within the first 2.7 weeks, whereas it took 8.1 weeks for a significant increase in HRV to be seen in the group taking soy oil.  None of the study participants experienced significant negative side effects, but 41% of participants in the fish oil group reported belching, compared to 16% in the soy oil group.