Yet another study has been released that clinches the principal-perhaps the only-reason why the Japanese have so much less heart disease than Americans.
The Japanese experience only one third of the heart attacks of Americans, and Japan occupies the bottom of the list with least heart attacks among all developed countries.
A new study provides powerful new evidence that it is the omega-3 fatty acids from fish that confer much, if not all, of these benefits.
The Electron-Beam Tomography, Risk Factor Assessment Among Japanese and U.S. Men in the Post-World War II Birth Cohort Study, or ERA JUMP for short, a collaborative U.S.-Japanese effort, is a fascinating study that compared three groups of men: 281 Japanese men living in Japan, 306 non-Japanese men living in the U.S. (Pittsburgh, Pennsylvania), and 303 Japanese Americans (having both parents Japanese without "ethnic admixture") living in Hawaii. The last group was included to represent a group that is the same genetically as the group in Japan, but exposed to something close to a "typical" American diet and lifestyle.
Three main measures were compared: blood levels of omega-3 fatty acids (EPA, DHA), carotid intimal-medial thickness (CIMT, the thickness of the carotid artery lining that can serve as an index of body-wide atherosclerosis), and coronary calcium scores (obtained on the electron-beam heart scan device and serving as an index of coronary atherosclerosis and heart attack risk).
Interestingly, at the start of the study, the Japanese men, though more slender (BMI 23.6), were more likely to be smokers, alcohol drinkers, and had more high blood pressure than the Americans, and were less likely to take cholesterol medicationsâ”€all in all, a risk profile that in some measures predicted greater probability of heart disease and atherosclerosis. The Americans, conversely, while heavier (BMI 27.9), were less likely to be smokers and drinkers, and had a four-fold greater use of cholesterol medications.
The Japanese Americans (in Hawaii) were the most likely to be hypertensive, diabetic, with a similar proportion of overweight as the non-Japanese Americans.
But here’s the surprising part: Despite the overall greater heart disease risk for profile for Japanese men, compared to non-Japanese Americans they had 10% less CIMT. In addition, only 9.3% of Japanese men had abnormal coronary calcium scores vs. 26.1% of non-Japanese Americans. Japanese-Americans were the worst, however, with nearly 10% more CIMT than non-Japanese Americans and 31.4% with abnormal calcium scores.
"Our results suggest that marine-derived n-3 [omega-3] fatty acids have antiatherogenic effects."
The most intriguing finding of all was the fact that, of all the various groups and degrees of atherosclerosis, whether gauged via CIMT or coronary calcium scores, the blood level of omega-3 fatty acids was inversely related, i.e., the greater the omega-3 blood level, the less plaque by either measure was detected. The Japanese men had the highest blood levels: twice that of the non-Japanese Americans. The Japanese-Americans had levels only slightly greater than non-Japanese Americans.
The editorial accompanying this study was written by omega-3 expert, Dr. William Harris, who calls omega-3 fatty acids the "Japanese Factor."
While other studies have persuasively demonstrated that omega-3 fatty acids substantially reduce heart attack, a weak link in the omega-3 argument has been a study that links greater omega-3 intake with less atherosclerosis. The unique approach of this study, employing two groups with sharply different omega-3 intakes, very powerfully argues for the plaque-inhibiting effects of this fraction of fats.
How much omega-3 fatty acids do Japanese people eat? Estimates vary, depending on part of the country, coastal vs. inland, age, urban vs. rural, etc., but Japanese tend to ingest anywhere from 5 to 15-times more omega-3 fatty acids than Americans. The actual intake of omega-3 fatty acids (EPA+DHA) in Japanese ranges from 850 to 3100 mg per day.
If you need yet another reason to add fish oil to your heart disease prevention program, the ERA JUMP experience surely clinches the argument. However, it is likely that the benefits of omega-3 fatty acid supplementation are not something that develop on Thursday after starting supplementation on Tuesday. Benefits require months to begin (as evidenced in the dramatic mortality reduction in the GISSI Prevenzione trial), but accumulate and likely extend beyond cardiovascular health after years. After all, the plentiful intake of fish by the Japanese is a lifelong habit.
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