Do Omega-3 Fatty Acids Prevent Heart Disease ?

 

omega-3 fatty acids

omega-3 fatty acids

Part two in recent articles taking a closer look at scientific evidence of omega-3 fatty acids, part 1 here.Do omega-3 fatty acids prevent heart disease and reduce risk of death ?

This article is based on two review articles, One published in the European Heart Journal in 2012 and one published in Current Cardiovascular Risk Rep in 2014.

There are droves of scientific studies exploring how omega-3 fatty acids correlate to the risk of various diseases, here we’ll explore heart disease.

Do Omega-3 Fatty Acids Prevent Heart Disease ?

A Diet of Fish

Coronary artery disease (CAD) are diseases affecting arteries supplying blood to the heart muscle, this class includes heart attacks, sudden death and angina . One study conducted by Kromhout and colleagues in 1985, followed 852 middle-aged men to determine if fish consumption was linked to death from CAD. They found that people eating more fish, over 30g per day, were more than 50% less likely to die from CAD. Eating more fish seemed to protect people from fatal heart disease.

This was one of many scientific studies that found a protective effect from a high-fish diet. Since 1985 many studies confirmed this correlation while others didn’t. In 1999 the first comprehensive review was published involving 11 studies, with a total of 116,764 individuals. This review concluded that the protective effect seen in people on a high-fish diet was real, but only in people already at high risk of fatal CADs, people at low risk of artery disease showed no positive effect from a high-fish diet.

In 2004 two meta-analyses took a closer look at fish consumption and the risk of dying from CAD. Meta analysis is when researchers select several studies and merge data in order to get better power in their study. These meta analyses had data on about 220,000 participants, each, with a follow-up period of about 12 years. From this data both studies found positive effects from including fish in their diet, one found 17% lower number of fatal CAD cases in people eating fish less than twice a week, compared to those eating no fish at all. This result was mirrored in the second meta analysis also finding that people eating fish five times, or more, each week had an even greater protective effect, 38% lower risk of dying from CAD.

Fish consumption together with scientific studies actually measuring levels of omega-3 fatty acids EPA and DHA, also confirm this protective effect. Preventing and reducing levels of CAD isn’t the only positive effect of a high fish diet. Some studies have found that a diet high in fish can also prevent sudden death and reduce the risk of death from heart attacks, though this evidence is weaker.

Fish Oil Supplements

So what about fish oil supplements?

A group of studies looking at supplementation of omega-3 capsules daily found that the supplements reduced potentially fatal disruptions of heart rhythm by 10%, while a meta analysis based on some of the same studies concluded an even greater effect (20%). The strongest effect was seen in studies on people who suffered heart attacks. Patients supplemented with EPA and DHA, both found in omega-3 supplements, had a 30%+ better survival compared to controls not taking the supplement.

The strongest effects observed in people given omega-3 supplements are in people not on modern drugs against high blood pressure, high cholesterol and blood thinners. This suggest that the positive effect of the supplements may be strongest when people are not already undergoing treatment for heart disease. This is probably also why some recent trials involving patients undergoing treatment for heart disease haven’t found any significant effect from omega-3 supplements.

Why some studies show, and other don’t show, a clear effect from the supplements might actually depend on a fairly obvious reason, blood levels of omega-3 fatty acids. Finding a positive effect varies wildly between studies, this difference is probably due to study design. Some studies might look at if people are simply taking supplements while other actually measures blood levels of the good fatty acids. This matters since some people taking omega-3 supplements don’t get high (enough) blood levels of the fatty acids, leading to varying results in the studies. In studies comparing blood levels of omega-3 fatty acids and heart diseases, there is a clear positive effect.

Image Credit: Jo Christian Oterhals via flickr.com, CC BY-NC-ND 2.0