Did the Japanese have it right about blood type all along?
I have worked in Japan for short periods on a couple of occasions (in 2007 and 2009) and have visited often. I really like Japanese culture, sport, the land and its people and their food. One thing that has really intrigued me is the cultural belief in blood types being important - from what you eat to who you marry. I have always been a sceptic about this, but there seems to be increasing evidence that blood type might be worth looking at further, especially when we talk about heart disease risk.
In an analysis of two large data sets (62,000+ and 27,000+), where people aged 30-75 were followed for 20 years or more, they found over and under representations of various blood types and the heart disease risk associated with having that type. Here's a summary:
- The rarest blood type - AB, found in only 7% of Americans (USA) - had the highest increased heart disease risk at 23%
- Those people with blood type B had an 11% increased risk
- Those with type A had a 5% increased risk
- About 43 percent of Americans have blood type O.
Although the research team considered the relative impacts of gender, race, diet, age, and other factors, they didn't offer an explanation as to the mechanism of the heart disease risk profile associated with particular blood types. There is other research suggesting that blood type A is associated with higher levels of LDL cholesterol (that's the bad cholesterol), and that type AB is linked to increased inflammation.
However, there is evidence suggesting that type A is associated with higher levels of low-density lipoprotein cholesterol, the waxy substance that can clog arteries, and type AB is linked to inflammation, which may affect the function of the blood vessels. This inflammation can be reduced through regular exercise - see my post here for details. Also, a substance that plays a favorable role in blood flow and clotting may be higher in people with type O blood may have a higher level of a substance that plays a positive role in blood flow and clotting - and that this may offer some protective effects against the development of heart disease.
This kind of research is useful because it offers a way forward in developing interventions for those who have increased risk for particular diseases. For example, a person with type A blood might be able to best reduce their heart disease risk through lowering cholesterol.
I have no idea how this relates to dietary advice that the Japanese who believe in the influence of blood types on various aspects of life, but I am sure there are people working on it right now. But it does show that although it is perhaps wise to keep a skeptical and wary eye out, paying attention to high quality evidence, it is also good to keep an open mind when the contrary or confirmatory evidence is presented before you.