Analysis of conflicting fish oil studies finds that omega-3 fatty acids still matter

November 28, 2012, Oregon State University

Literally hundreds of clinical trials, including some that have gained widespread attention, have been done on the possible benefits of omega-3 fatty acids for the prevention of heart disease – producing conflicting results, varied claims, and frustrated consumers unsure what to believe.

A recent analysis done by scientists in the Linus Pauling Institute at Oregon State University, published in the , has sorted through many of these competing findings, and it helps to explain why so many of the studies seem to arrive at differing conclusions.

The review concludes that both and dietary omega-3 may still help prevent heart disease; that some , from certain sources, are more effective than others; that these compounds may have enormous value for serious health problems other than heart disease; and that the very effectiveness of modern for heart disease may be one explanation for the conflicting findings on the benefits of omega-3 fatty acids.

"After decades of studying omega-3 fatty acids, it's clear that they have value in primary prevention of heart disease," said Donald Jump, author of the analysis, a principal investigator in the Linus Pauling Institute, and professor in the OSU College of Public Health and Human Sciences.

"It's less clear how much impact oils have in preventing further in people who already have ," Jump said. "The studies done several decades ago showed value even for that patient population, but the more recent studies are less conclusive. We believe that one explanation is the effectiveness of current state-of-the-art treatments now being offered."

Some of the earliest work that raised interest in omega-3 fatty acids was done in the 1970s with Greenland Inuits, who ate large amounts of fish and were found to have unusually low levels of . But, Jump said, millions of people now at risk for cardiovascular disease take medications such as statin drugs for high cholesterol; fibrates for high triglycerides; anti-thrombotics to thin their blood; and other drugs with anti-inflammatory or anti-arrhythmia effects.

Fish oils can have positive effects on virtually all of these same cardiovascular risk factors, Jump said, but so can the drugs.

"Some of the early studies done on fish oil were prior to so many effective medications being widely available and heavily used," Jump said. "And people often forget that nutrients, like fish oils, are less potent than prescription drugs, and often have their best value when used for extended periods.

"When so many people in these studies are taking a regimen of medications to address the same issues that fish oil might also affect, it's easy to understand why any added benefit from the fish oils is more difficult to detect," he said.

The point, Jump said, is not that omega-3 fatty acids have no value – they do. But for studies of their value in cardiovascular disease, which are often done when patients are taking other medications, that value is less clear.

A wide body of other research, he says, makes it clear that omega-3 fatty acids also have health benefits that go beyond cardiovascular disease. They have been shown to improve visual acuity; improve cognitive function and reduce dementia; reduce inflammation and perhaps some types of cancer, such as colon cancer; and reduce total mortality.

Among the findings of this review:

  • An important type of omega-3 fatty acid for human health is DHA, which is the predominant omega-3 fatty acid that accumulates in tissues.
  • Plant-derived sources of these fatty acids, such as flaxseed oil or chia seeds, have less benefit than those from cold-water fish, because of differences in how the human body processes these nutrients.
  • For individuals unwilling or unable to consume fish or supplements, some products made from yeast or algae are high quality.
  • It's difficult to be certain of the amount of in farm-raised fish, since these fish require dietary omega-3 supplementation.
"We still believe the evidence is strong that the EPA and DHA content in heart tissues and blood is important to health and to the prevention of cardiovascular disease," Jump said. "To meet the current recommendations for primary prevention of cardiovascular disease, individuals are advised to consume 200-300 milligrams of combined EPA and DHA per day."

Explore further: Omega-3 supplements no help against repeat heart trouble: review

Related Stories

Omega-3 supplements no help against repeat heart trouble: review

April 9, 2012
(HealthDay) -- Taking omega-3 fatty acid supplements won't protect against repeat heart attacks, strokes or other cardiovascular problems, a new analysis indicates.

Young women may reduce heart disease risk eating fish with omega 3 fatty acids

December 5, 2011
Young women may reduce their risk of developing cardiovascular disease simply by eating more fish rich in omega-3 fatty acids, researchers reported in Hypertension: Journal of the American Heart Association.

Omega-3 fatty acids may help to reduce the physical harm caused by smoking

April 20, 2012
Omega-3 fatty acids may help to reduce the physical harm caused by smoking, according to a new study presented at the World Congress of Cardiology.

Role of omega-3 in preventing cognitive decline in older people questioned

June 12, 2012
Older people who take omega-3 fish oil supplements are probably not reducing their chances of losing cognitive function, according to a new Cochrane systematic review. Based on the available data from studies lasting up to ...

Recommended for you

Calcium and Vitamin D supplements are not associated with risk of heart attacks

February 16, 2018
New research from the University of Southampton has found no association between the use of calcium or vitamin D supplementation and cardiovascular events such as heart attacks.

Study shows options to decrease risk of motor vehicle crashes for adolescent drivers

February 16, 2018
Adolescents who receive comprehensive and challenging on-road driving assessments prior to taking the license test might be protected from future motor vehicle crashes, according to a University of Alabama at Birmingham study ...

Being a single dad can shorten your life: study

February 15, 2018
The risk of dying prematurely more than doubles for single fathers compared to single mothers or paired-up dads, according to a study of Canadian families published Thursday.

Keeping an eye on the entire ageing process

February 15, 2018
Medical researchers often only focus on a single disease. As older people often suffer from multiple diseases at the same time, however, we need to rethink this approach, writes Ralph Müller.

Study suggests possible link between highly processed foods and cancer

February 14, 2018
A study published by The BMJ today reports a possible association between intake of highly processed ("ultra-processed") food in the diet and cancer.

Muscle more important than fat in regulating heat loss from the hands

February 14, 2018
In the first study of its kind, Cambridge biological anthropologists have shown that muscle mass is able to predict the rate of heat loss from the hands during severe cold exposure, while body mass, stature and fat mass do ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.