Recently I was introduced to a friend of a friend, a dedicated vegan, raw-foodist, and from what I understood, since recently also following the “blood type diet”.
From the reasonable down to the bizarre
Now, I understand the reasons behind veganism. If you think animals have just as much right to a free life as humans, it makes sense not to eat products derived from animals that are not free. Eating only raw foods sounds a bit odd, but OK, I can see some idea to not diminishing the vitamins in fruit and veggies by boiling them (but maybe I do should look into it, given what I’m going to say about the blood group diet). I still don’t understand why you wouldn’t want to eat rice or potatoes, which actually become edible upon boiling, but OK.
But a diet based on what blood type (or “group”) you have? That just sets my sceptical alarm bells off ringing.
I didn’t want to insult somebody who I’d only just met an hour before, so I just smiled politely, but the “reasons” this person gave for it working sounded exactly like the reasons that people give when they claim homeopathy works. “No, there is no scientific evidence it works, because it’s too complicated for medical tests.” “Yes I know it contradicts the theory that you as type A can eat this without problem, but there’s more than just the blood groups – there are a lot of individual exceptions.” “I felt a lot better after I started following this diet, so I’m sure it works”. If that sounds familiar it’s because that’s how all of pseudoscientific alternative medicine – not just homeopathy – always carves its own niche.
Anyway, the premise of the whole theory, that because of the evolutionary history of blood groups you should eat the type of food associated with the time at which these blood groups came about (that is, if you accept all of that as true – even that is all very much debatable, if not just codswallop – a critical look at the distribution of blood types as given here should be a good start), sounds unlikely to begin with. Why would the blood group be affected by that? Why not your intestines? Anyway, I decided to have a little look later. Which is, now.
And, only a brief search confirms my original thought:
The blood type diet is, as expected, a load of crap.
Only two web pages, combined with your own rational critical thinking abilities, should suffice to convince oneself it is so.
Wikipedia is actually really brief, because there just isn’t a lot to this diet, so I won’t even link there.
The Skeptics Dictionary does a good job at quickly getting to the point of why there is no scientific basis to this diet. On the other hand a more practical review is given here, by people who you expect should know about it; and I was actually expecting them to be less sceptical about it!
Oh, the curse of gullible people!