Findings appear to eliminate genetic explanations for Japan’s low rates of heart disease.
by Craig Weatherby
The results of a new study affirm the idea that consuming fish or fish oil frequently can reduce the risk of cardiovascular disease and consequent injuries or death.
It’s long been known that people in fish-loving Japan have much lower rates of heart disease, compared with Americans and most Europeans.
The same is true of Iceland and other countries where fish consumption is high.
Rates of coronary heart disease and heart-related deaths remain very low in Japan despite major shifts toward American-style diets and lifestyles: an anomaly called the “Japanese paradox”.
And new findings essentially eliminate the possibility that genetic differences between Japanese and Americans could explain Japan’s heart-health advantage.
Japan’s reduced heart risk rates linked to fish, not genes
An international team from Japan, Pennsylvania, Virginia, and Hawaii examined blood samples and health records of Japanese men, white American men, and Japanese-American men (Sekikawa A, et al. 2008).
The results showed that the Japanese men had omega-3 blood levels two times higher than white Americans or Japanese-Americans, and that the Japanese men had the lowest levels of atherosclerosis (dangerous arterial plaque).
Lead author Akira Sekikawa from the University of Pittsburgh made two important points in a press release:
- “Our study suggests that very high levels of omega-3 fatty acids have strong properties that may help prevent the buildup of cholesterol in the arteries.”
- “Our study shows [that the] much higher intake of fish observed in the Japanese may have strong anti-atherogenic [plaque-preventing] effect.”
Dr. Sekikawa's team examined blood and health data from 868 men between 40 and 49 years of age.
Of these, 281 were born and living in Japan (Japanese), 306 were white men born and living in the U.S. (white American), and 281 were men of Japanese ancestry born and living in the U.S. (Japanese-American).
To rank the men’s risk of atherosclerosis, the researchers measured the intima-media thickness (IMT) of the carotid artery, which provides a pretty good indication of the presence and severity of atherosclerotic plaque.
The Japanese men had the lowest levels of atherosclerosis, as measured by their carotid arteries' IMT.
And the Japanese advantage held steady after the researchers accounted for other plaque-promoting factors such as higher cholesterol levels, blood pressure, cigarette smoking, higher body mass index, and diabetes.
The Japanese-Americans and the white Americans had similar levels of LDL cholesterol, but the white American men had significantly higher levels of the riskiest form of cholesterol (large VLDL) and significantly lower levels of the most protective kind (large HDL).
The team’s conclusion summarizes their finding succinctly:
“Very high levels of marine-derived omega-3 fatty acids have anti-atherogenic [plaque-preventing] properties that are independent of traditional cardiovascular risk factors and may contribute to lower the burden of atherosclerosis in Japanese, a lower burden that is unlikely the result of genetic factors.” (Sekikawa A, et al 2008)
Heart risks of “omega imbalance”
We’ve published many reports on research that indicates a strong relationship between over-consumption of omega-6 fatty acids and increased risk of most major health risks, including cancer, diabetes, Alzheimer’s and cardiovascular disease.
The most recent was a report on studies from Israel and Korea: see “Womens’ Excess Omega-6 Intake Raises Health Risks.”
To read more on this subject, go to our newsletter archive and search for “omega-6.”
- Sekikawa A, et al. Marine-derived n-3 fatty acids and atherosclerosis in Japanese, Japanese-American, and white men: a cross-sectional study. J Am Coll Cardiol. 2008 Aug 5;52(6):417-24.
- Sekikawa A, et al. Intima-media thickness of the carotid artery and the distribution of lipoprotein subclasses in men aged 40 to 49 years between whites in the United States and the Japanese in Japan for the ERA JUMP study. Metabolism. 2008 Feb;57(2):177-82.
- Sekikawa A, et al. Less subclinical atherosclerosis in Japanese men in Japan than in White men in the United States in the post-World War II birth cohort. Am J Epidemiol. 2007 Mar 15;165(6):617-24. Epub 2007 Jan 22.
- Yokoyama M, et al. Effects of eicosapentaenoic acid on major coronary events in hypercholesterolaemic patients (JELIS): a randomised open-label, blinded endpoint analysis. Lancet. 2007 Mar 31;369(9567):1090-8. Erratum in: Lancet. 2007 Jul 21;370(9583):220.