Lessons about omega-3s from Japan

Image courtesy of apc33.

Japan provides a useful "laboratory" for studying the effect of a culture that relies heavily on eating fish.

The JELIS Trial, the topic of a previous Heart Scan Blog post, showed that supplementation with the single omega-3 fatty acid, EPA, 1800 mg per day (the equivalent of 10 capsules of 'standard' fish oil that contains 180 mg per day of EPA, 120 mg of DHA) significantly reduced heart attack in a Japanese population. Interestingly, this benefit was additive to the already substantial intake of omega-3 fatty acids among the general Japanese population, a population with a fraction of the heart attacks found in western populations like the U.S. (approximately 3% over 5 years in Japanese compared to several-fold higher in a comparable American group).

While there may be genetic and other cultural and lifestyle reasons behind the dramatically reduced cardiovascular risk in Japanese, it is undeniably at least partially due to the increased intake of omega-3 fatty acids from fish. Incidentally, the purported benefits of omega-3 fatty acids provide a vigorous counter-argument to the idea that all humans should be vegetarians.

Anyway, if we were to take some lessons from the Japanese and their greater habitual intake of omega-3 fatty acids from fish, they might include:

--Rural and coastal Japanese are the sub-populations with the highest reliance on fish, about a quarter-pound a day. (Gives new meaning to the idea of a "Quarter Pounder," doesn't it?) This is at least five-times greater than the intake of an average American.

--Likewise, the blood level of omega-3s in the blood of Japanese is 5-fold higher than in Americans.

--The average intake of omega-3s (EPA + DHA) among a broadly-selected population of Japanese is 850 mg per day (320 mg EPA; 520 mg DHA). Intake ranges from 300 mg per day all the way up to 3100 mg per day.

--Greater omega-3 intake (EPA + DHA) is associated with lesser carotid intimal-medial thickness, an index of body-wide atherosclerosis.

--Japanese have far less heart attack and stroke despite greater prevalence of smoking (nearly half of Japanese) and drinking.

--Total fat intake (percent of calories) is nearly identical between Americans and Japanese. It's the proportion of fat calories from omega-3 that is greater, the proportion of omega-6 that is less in Japanese.

The Japanese eat their fish in ways that we do not: As sashimi (raw, as with sushi in its various forms like Nigiri and Chirashi); fried in tempura; shaved, dried fish sprinkled on about anything you can imagine (it's not as bad as it sounds); as a snack, as in dried cuttlefish (which you can purchase in packages as a portable, sweetened fish that you eat on-the-run--I know it sounds awful, but don't poke fun at it until you've tried it); in "soups" with soba noodles. Fish is commonly consumed with rice and soy sauce, as well as other soy-based foods, such as tofu, miso (soy bean paste), or natto. 

I believe that there are some lessons to take from the Japanese and their fish-consuming habits:

1) An omega-3 fatty acid intake of at least 1000 mg per day yields measurable cardiovascular benefits. 

2) Despite the fears over mercury and pesticide residues in fish, this seems to not have played out to be a real-life effect in the Japanese, who consume five-fold greater quantities of fish. 

3) My mother was right after all when she encouraged us to eat more fish. 

Comments (7) -

  • Juhana Harju

    7/23/2008 2:24:00 PM |

    Currently the Japanese get 25 percent of their calories from fat which means that it is lower in fat than the average American diet. Traditionally the Japanese diet has been very low fat, only about 10 E% from fat. Taking into account that degenerative illnesses have a time lag, the previous consumption of very low fat diets is still affecting to the health of Japanese people.

  • Ross

    7/23/2008 3:43:00 PM |

    The French and Spanish have a substantially higher fraction of calories from fat than Americans and also enjoy a lower rate of heart disease.

    Hint: fat and saturated fat are probably not to blame for heart problems.

  • LeenaS

    7/24/2008 8:20:00 AM |

    Japanese may have eaten low-fat, but even there the increase in fat did increase the life span, too.

    Okinawans were not only known for their longevity but also for their food that was regarded very fatty in terms of the general Japanese food culture.

  • Gyan

    7/24/2008 11:24:00 AM |

    1) Cant canola/rapeseed oil provide ALA (DHA/EPA precursor).
    In a low-PUFA diet, the conversion is supposed to be efficient.
    2) Some researchers claim that EPA is not required in human body though DHA is necessary.
    3)The high levels of DHA/EPA intake might reduce heart disease but could they cause other problems such as cancer, strokes etc.
    What is the optimal level of omega-3 intake?

  • Jeff Consiglio

    7/24/2008 2:33:00 PM |

    My understanding is that the Japanese have lower rates of heart attacks, but higher rates of hemorrhagic stroke than in the US. Anyone else heard this?

  • Anonymous

    7/25/2008 4:42:00 PM |

    --Omega-3 intake (EPA + DHA) is associated with carotid intimal-medial thickness, an index of body-wide atherosclerosis.

    I assume you meant to say a reduced cartoid intimal-thickness? Or would an increased thickness = less atherosclerosis?

    And the increased rate of  hemorrhagic (bleeding type) stroke would make some sense, as I believe Eskimos had the same problem. But the risk of heart disease or other types of strokes are much more of a risk factor anyway.

  • Dr. William Davis

    7/26/2008 1:36:00 PM |

    Yes. I should have said that EPA + DHA are inversely associated with carotid intimal-medial thickness.