Help me prove to my mom blood type diets are crap

[EeneyMinnieMoe]

My mom recently bought a book about blood type diets. Only eating what's right for your blood type. She's reading it cover to cover and yakking about it day and night to her friends and is trying to get me to get on it.

It's pure pseudoscience- it's half true facts about blood and half fake dieting mumbo jumbo. Such as type A rejects such and such antigens so therefore don't eat tomatoes.

I tried to explain to her that it came from Japan and derives from their superstitions and mysticism but that made her believe it even more!

Cause the Japanese are really advanced in science and perfected cell phones and DVD players.

[MelBrooksfan]

You could try the basics: Point out the obvious logical failings.

Failing that, find that some of their claims have no backing. I.E. that chemicals/antigens/reincarnated saints X and Y are present in tomatoes, go show that, in fact, they are not present in tomatoes (if, indeed, they aren't).

[tkingdoll]

Oh, I gathered some info on this last year, I will look for it tonight as I had some great debunking stuff.

IIRC there was something on skepdic; might be a good place to start.

[kerikiwi]

It's very difficult when people are determined to be ignorant.
I have a colleague who followed this 'diet'. She has got to a very healthy weight, and looks svelte and energetic.
She also walks and goes to the gym, as well as having given up smoking and drinking.
Clearly it is a scientifically based diet.

[neon]

Tell her to do the diet for the wrong blood type. See what happens.

[kerikiwi]

She might stop exercising, and take up smoking and drinking again.

[TV's Frank]

She might stop exercising, and take up smoking and drinking again.

Diet for Type A: Exercise often, stop drinking and smoking.

Diet for Type O: Do not exercise. Drinks and smokes are on us.

[nails3jesus0]

If I were to explain to her how your blood type doesnt matter when it comes to diet, I would tell her that foods get digested and proccessed in the digestive system into their basic elements and distributed based on their content, and that there is no way for your blood to know if a gram of fat came from cashews or avacados after its been broken down that much.

also, i would question what the 'reaction' supposedly is. If the theory is that a reaction in blood to food causes someone to gain weight, well, there either are calories ready to be stored as fat or there arent any. blood cells cannot magically produce excess calories no matter what you do to them. And you could bring up the fact that when blood transfusion recipients have a bad reaction based on blood type the host's red blood cells basically explode, i dont see why (in her theory) everyone would not be dead from a reaction to foods if blood cells reacted to foods like they do to incompatable blood cells.

[The SkepDoc]

I didn't think it was Japanese. The Japanese have a personality "astrology" based on blood types, but I think the diet/blood type concept is a Western one. Dr. Peter D'Adamo wrote the book that is usually quoted on this subject. I've read his claims and looked at the studies he quotes, which don't mean what he claims they say. The whole thing is pure pseudoscience. You can read a debunking of blood type diets at http://www.quackwatch.org/04ConsumerEducation/NegativeBR/d'adamo.html

Have your Mom read this, then have her read what the Skeptics Dictionary and Wikipedia have to say about it. http://skepdic.com/bloodtypediet.html and http://en.wikipedia.org/wiki/Blood_type_diet

If she reads those and still believes her book, she is probably a lost cause.

[BPSCG]

Sounds like she's reading Eat Right 4 Your Type, by a naturopath named Peter D'Adamo. Friend of mine was a big fan a few years ago; I told her it sounded like a buncha crap to me. I emailed D'Adamo to ask him if his work had been peer-reviewed. I was shocked - shocked - that I never got a reply.

I then went to an sci.med.nutrition newsgroup and asked the same question, and got a reply from a doctor who said she reviewed the latest published articles on nutrition every week, and had never seen it published for peer review.

So you might want to ask your mom, "If this is genuine science, why doesn't he publish his findings for peer review?"

Here's a link from a review of the book on quackwatch.com (http://www.quackwatch.org/04ConsumerEducation/NegativeBR/d'adamo.html): The final paragraph (emphasis is mine):

It may well turn out that there are important interactions with between certain foods and one's blood type. D'Adamo, unfortunately, offers little in the way of scientific evidence, relying instead on a collection of anecdotal reports and case histories. His speculation that the one gene responsible the ABO blood type could exert such a dominant influence over everything else is unable to stand on its own merits. In the end, D'Adamo adds the caveat that individual variations still occur within blood types, so you shouldn't expect all of his recommendations to apply to you. It's nice to have it both ways, especially where book sales are involved.

[strathmeyer]

Usually when somebody claims that some particular diet is especially healthy, you can stop the dead in their tracks by asking them to produce a healthy person who follows the particular diet.