Blood types in Japan

During one of my lessons, my student asked me what type of blood I have, which struck me as an odd inquiry. He was surprised and slightly concerned when I replied that I didn't know. In Japan, virtually everyone knows their blood type - my host siblings' luggage tags list their names, phone numbers, and blood type - and many use it to predict a person's character.

I've verified this with a number of Japanese people and while not all of them truly believe the characterizations, some of them were firm followers; one woman even said she took blood type into account when she went on dates. I don't have a solid understanding of the distinctions, but this is what I have gathered. I have also heard that there are charts with recommended nutrition for different blood types, but I don't know the details. If you know your blood type, check to see if you match these traits:

Type A: empathetic, organized, hospitable, detail-oriented, punctual, neat, calm in crisis, not a risktaker

Type B: independent, happy-go-lucky, optimistic, flexible, playful, party-hardy, likes company, risktaker

Type AB: a dreamer, spiritual, sensitive, private, studious, creative, curious

Type O: realistic, hard worker, ambitious, cautious, leader

I have two sets of host parents and in both couples the mom is type A and the dad is type B. Opposites attract, they told me. My hosts moms both think I'm type AB. Now I'm curious to find out!