Release Date:
July 27, 2010
July 26, 2010
Fish Linked to Heart-Diabetes Risks
Korean-American team finds fish-loving men less likely to develop metabolic syndrome: No risk reduction seen in women, who ate less fish on average
by Craig Weatherby, edited by Amron Bevels-Wilson, MD
Fish Linked to Heart-Diabetes Risks
Korean-American team finds fish-loving men less likely to develop metabolic syndrome: No risk reduction seen in women, who ate less fish on average
by Craig Weatherby, edited by Amron Bevels-Wilson, MD
Metabolic syndrome is a group of risk factors for diabetes, heart disease, and stroke … and one of the hottest topics in preventive medicine.
Having metabolic syndrome – called MetS for short – doubles your risk of heart attack and stroke.
So there’s been a rush to find ways to deter the several risk factors that, taken together, produce a diagnosis of metabolic syndrome.
MetS is diagnosed as the combination of central obesity AND any two of the following proven risk factors for diabetes, stroke, and heart disease:
- High blood pressure
- High triglyceride levels
- High blood sugar levels
- Low levels of HDL (“good”) cholesterol
Now, the results of an epidemiological (diet-health) study from Korea link frequent fish consumption to a sharply reduced risk of being diagnosed with MetS.
This study is the first to link frequent fish consumption with a reduction in the risk of a MetS diagnosis, rather than a drop in the risk of one or two of its defining components.
Korean-American team finds reduced risk in fish-loving men
Researchers from Seoul’s Kookmin University recruited 3,500 Korean adults aged 40 to 69, had them fill out detailed diet surveys, and examined their health periodically over a three-year period (Baik I et al. 2010).
After the results were adjusted to account for other risk factors for MetS, the team determined that men who ate fish daily were 57 percent less likely to develop metabolic syndrome over three years, compared with those who dined on fish less than once a week.
About 12 percent of the 232 men who said they ate fish every day developed metabolic syndrome over the next three years.
In contrast, 16 percent of the 190 men who reported eating fish less than once a week developed metabolic syndrome.
However, the study detected no link between fish-eating and lower MetS risk among women.
Women got no benefit, but ate less fish than men
Why would frequent fish intake be less protective for women than for men?
The answer may lie in the relatively smaller amounts of fish eaten even by women … even among the women who reported eating the most fish.
The men who ranked in the top 10 percent of estimated omega-3 intake (from fish) averaged 786mg of omega-3s per day while their fish-loving female counterparts – whose MetS risk did not go down – averaged only 563mg.
Likewise, the men who consumed the most omega-3s showed a lower risk of MetS than those in the bottom 10 percent.
According to the Korean researchers, that outcome supports the presumption that it was higher omega-3 intake from fish that accounted for the connection between eating more fish and having a reduced risk of metabolic syndrome.
Therefore, the researchers suggested, even the women who reported the highest fish intake may not have gotten enough omega-3 fatty acids to gain a reduction in the risk of MetS.
Like other epidemiological studies, this one cannot by itself prove a cause-and-effect relationship between higher fish intake and lower risk of MetS.
While we need more large, rigorously designed trials to draw definitive conclusions (Filion KB et al. 2010), the many official advisories urging people to eat more fish and/or supplemental omega-3s rest on an enormous body of highly persuasive, mutually reinforcing evidence of every kind.
How much fish and omega-3s are needed?
Expert bodies worldwide recommend consuming 250 to 1000mg of EPA and DHA daily – the amount in a substantial, 3 to 6 oz serving of fatty fish for heart health.
The available evidence suggests that 250mg is enough for women, but the Korean findings suggest a need for more gender-specific study.
The American Heart Association recommends eating two servings of fatty fish every week, such as salmon, sardines, mackerel, tuna, or sablefish.
The various signs that together provoke a diagnosis of metabolic syndrome are prevented by healthy weight, not smoking, regular exercise, and a balanced diet rich in fruits, vegetables, and high-fiber foods.
Most researchers now agree that to help prevent MetS, we should eat fewer polyunsaturated omega-6 fats than the average American – replacing them primarily with polyunsaturated omega-3 fats from fish (EPA and DHA) – and secondarily with monounsaturated omega-9 fats (oleic acid) from olives/olive oil, avocadoes, macadamia nuts/oil, and special “hi-oleic” sunflower oil.
Wild salmon offers a superior fatty acid profile in this regard, compared with farmed, grain-fed salmon.
Both kinds are equally high in omega-3s, but farmed salmon has much more pro-inflammatory omega-6 fat, which Americans consume (from vegetable oils and packaged/prepared foods) in the large amounts now linked to major diseases.
The short-chain, plant-derived omega-6 fats that abound in farmed fish also compete with fish-borne omega-3s for absorption into our cells.
Sources
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- Baik I, Abbott RD, Curb JD, Shin C. Intake of fish and n-3 fatty acids and future risk of metabolic syndrome. J Am Diet Assoc. 2010 Jul;110(7):1018-26.
- Bucher HC, Hengstler P, Schindler C, Meier G: N-3 polyunsaturated fatty acids in coronary heart disease: a meta-analysis of randomized controlled trials. Am J Med 2002, 112:298-304.
- Filion KB, El Khoury F, Bielinski M, Schiller I, Dendukuri N, Brophy JM. Omega-3 fatty acids in high-risk cardiovascular patients: a meta-analysis of randomized controlled trials. BMC Cardiovasc Disord. 2010 Jun 3;10:24.
- Hooper L, Thompson RL, Harrison RA, Summerbell CD, Ness AR, Moore HJ, Worthington HV, Durrington PN, Higgins JP, Capps NE, et al.: Risks and benefits of omega 3 fats for mortality, cardiovascular disease, and cancer: systematic review. BMJ 2006, 332:752-760.
- Hu FB, Bronner L, Willett WC, Stampfer MJ, Rexrode KM, Albert CM, Hunter D, Manson JE. Fish and omega-3 fatty acid intake and risk of coronary heart disease in women. JAMA. 2002 Apr 10;287(14):1815-21.
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