The Japanese have the lowest incidence of heart attack in the world, yet they have the same rates of high cholesterol, high blood pressure and diabetes, and they smoke as much as Americans do. It's not because of their genes because Japanese who move to Hawaii and the continental United States have a significant rise in their heart attack rates and the same amount of plaques in their arteries as Americans ( Journal of the American College of Cardiology, August 5, 2008).
On the average, Japanese in Japan eat fish eight times a week and they add far less vegetable oils to their prepared foods. This study shows that Japanese living in Japan have twice as much long-chain omega-3s in their blood as those who left Japan. They also have lower blood levels of omega-6 polyunsaturated fatty acids, and fewer plaques in their arteries.
Fats are classified by their chemical structure into saturated, polyunsaturated, and monounsaturated. Polyunsaturated fats are further sub-classified into omega-3, omega'6 and omega-9. Increasing the ratio of omega-6s to omega-3s increases heart attack risk. For two million years, the typical human diet contained a ratio of omega-6s to omega-3s of about two to one. Today we take in large amounts of omega- 6s in the form of extracted vegetable oils and not enough omega-3s from fish, shellfish and some seeds. Now our ratio of omega-6s to omega-3s has risen beyond 12 to one.
We now think that heart attacks are caused to a large extent by an overactive immunity called inflamation. Your immunity is supposed to protect you from infection. However, if your immunity stays active all the time, it attacks you and starts to destroy every tissue in your body, particularly your blood vessels. Omega-3s form certain chemicals in your body called prostaglandins that turn off your immunity. Omega-6s form prostaglandins that turn on your immunity. The activity of your immunity changes with the ratio of omega-6s to omega-3s. For a heart-healthy diet, add more seafood and whole seeds, and eat less of the foods made with polyunsaturated vegetable oils.