A comprehensive review of studies on the benefits of omega-3 consumption has led scientists to recommend the establishment of a Dietary Reference Intake (DRI) for EPA and DHA to reduce the risk of heart disease.
The strength of evidence linking eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to a reduced risk of coronary heart disease was “remarkable”, they said, prompting them to recommend a DRI of between 250 and 500mg/day.
In 2002, the US Institute of Medicine (IOM) concluded that there was insufficient evidence to define DRIs for EPA and DHA. The current review, based on a workshop organized last year by the Technical Committee on Dietary Lipids of the International Life Sciences Institute of North America, was designed to examine new data that have emerged since 2002.
The workshop aimed to examine evidence of the benefits of EPA and DHA on coronary heart disease (CHD), cancer and cognitive decline.
In a supplement published this year in The Journal of Nutrition and based on the workshop conclusions, the scientists stated that while evidence was clear for the benefits of EPA and DHA for reducing the risk of CHD, there was not enough consistent evidence on the benefits of the omega-3s for cognitive health and cancer reduction.
These findings add momentum to the drive to establish an omega-3 DRI, a move that has long been supported by the research community and the food and dietary supplement industries.
The scientists reviewed over 15 prospective cohort studies in generally healthy populations, a retrospective case-control study of sudden cardiac death, four large randomized controlled trials with fish or fish oil in patients with and without known heart disease, and several in vivo and animal experimental studies.
This evidence indicates that modest EPA and DHA consumption “markedly” reduces the risk of cardiac death, they said.
“The quality, strength, and concordance of this evidence are remarkable, meeting and indeed generally exceeding those for any other dietary factor for which a DRI has been set based on reducing risk for chronic disease, including saturated fat, dietary cholesterol, salt, and dietary fiber,” they wrote.
“For primary prevention of cardiac death, the leading cause of death in both men and women in the United States and nearly all other developed nations, current evidence supports a DRI for EPA1DHA between 250 and 500 mg/d.”
However, the scientists found that evidence was “more modest” for the effects of long-chain polyunsaturated fatty acids (PUFA) on other cardiovascular risks, including blood pressure, resting heart rate, triglyceride levels and heart rate variability.
Cognitive and cancer benefits
The review also included emerging data on the cognitive and cancer benefits of EPA and DHA.
The evidence for protective effects of omega-3 long chain PUFA from fish on risk of dementia is “promising but limited”, said the scientists.
Epidemiological evidence suggests positive benefits of one fish meal per week on the risk of Alzheimer’s disease, dementia, and cognitive decline. In addition, the animal evidence and biologic plausibility support a protective relation of omega-3 long-chain PUFA on neurodegeneration of the brain with aging. However, tissue DHA levels do not seem to be consistently lower in Alzheimer’s disease or any form of cognitive decline associated with aging, said the scientists.
“Several primary and secondary prevention trials are in progress in the United States and Europe that will greatly inform the field. Further research is necessary to examine the effects of different dose levels, benefits of DHA, EPA, and ALA, and the importance of relative intakes of [omega-3] vs. [omega-6] fatty acids”.
In relation to the cancer benefits of omega-3s, the researchers concluded that “there are no clear relations between dietary intakes of EPA and DHA and risk for cancer.”
Towards Establishing Dietary Reference Intakes for Eicosapentaenoic and Docosahexaenoic Acids
The Journal of Nutrition
First published online February 25, 2009; doi:10.3945/jn.108.101329.
Authors: William S. Harris, Dariush Mozaffarian, Michael Lefevre, Cheryl D. Toner, John Colombo, Stephen C. Cunnane, Joanne M. Holden, David M. Klurfeld, Martha Clare Morris, and Jay Whelan