Harvard team ranks low omega-3 intake as the sixth highest preventable killer among a dozen dietary, lifestyle and metabolic risk factors for mortality 05/25/2009
The authors of new study calculate that a deficiency of omega-3 fatty acids in the diet causes up to 96,000 preventable deaths annually in the United States.
Among the dozen dietary, lifestyle and metabolic risk factors examined by researchers at the Harvard School of Public Health, low omega-3 intake ranked as the sixth greatest killer, responsible for about 84,000 preventable deaths in 2005.
Tobacco smoking was blamed for 467,000 preventable deaths, followed by high blood pressure (395,000), obesity (216,000), physical inactivity (191,000), high blood sugar (190,000), high LDL cholesterol (113,000), and high salt intake (102,000).
Causing 84,000 preventable deaths, low omega-3 intake was found a greater risk factor than high intake of trans fatty acids (82,000 preventable deaths), found in hydrogenated vegetable oils (Danaei G et al. 2009).
Each risk factor was assigned a range of likely deaths, with low omega-3 intake causing from 72,000 to 96,000. The researchers averaged the low and high estimates to arrive at a figure of 84,000 preventable deaths.
The study was an analysis of data from the huge, regularly repeated U.S. National Health and Nutrition Examination Survey (NHANES), which is one of the best of its kind in the world.
How did they define “low omega-3 intake”?
First, the Harvard team defined “omega-3s” as the long-chain type found in fish (EPA and DHA), not the less useful short-chain omega-3 (called ALA) found in some plants.
Then they divided 20,470 NHANES participants into 5 groups, based on their omega-3 intakes.
The lowest risk was seen among people who consumed 250mg or more of omega-3s per day, and the greatest risk was among those who consumed less than 187.5mg per day.
Most world health authorities recommend taking 500mg or more per day, and the American Heart Association recommends that heart patients take 1,000mg per day under medical supervision.
For comparison, a 3.5 oz serving of wild salmon contains from 1,200mg to 2,300mg (1.2g to 2.3g), depending on species.
There are three primary reasons for the study's high ranking of omega-3 deficiency as a risk factor for preventable death:
- Omega-3s are proven to prevent stroke, second heart attacks, and sudden cardiac death, which is responsible for half of all heart-related deaths.
- Omega-3s appear to reduce depression, which is linked to heart disease and suicide.
- Omega-3s are critical to proper immune function.
And many studies in animals and in human subjects and isolated cells suggest myriad ways in which omega-3s may benefit overall health and immunity.
We spoke with and heard co-author Dariush Mozaffarian, M.D. speak at the 2005 Seafood & Health conference in Washington, D.C., concerning his group's many studies on the health effects of omega-3 fatty acids.
These include evidence reviews concluding that the risk of mercury in ocean fish is outweighed by the benefits of eating all but those few species with high levels (shark, swordfish, tilefish, king mackerel, and grouper).
Aside from fish oils, omega-3s abound in clearly safe fatty fish species like salmon, sardines, sablefish, mackerel, and tuna (We select only small, young albacore to ensure minimal mercury content).
- Danaei G, Ding EL, Mozaffarian D, Taylor B, Rehm J, Murray CJ, Ezzati M. The preventable causes of death in the United States: comparative risk assessment of dietary, lifestyle, and metabolic risk factors. PLoS Med. 2009 Apr 28;6(4):e1000058. Epub 2009 Apr 28.
- Mozaffarian D, Rimm EB (2006) Fish intake, contaminants, and human health: evaluating the risks and the benefits. JAMA 296: 1885–1899.