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Theory behind popular blood-type diet debunked

January 16, 2014

TORONTO, ON – Researchers from the Uni­ver­si­ty of Toron­to (U of T) have found that the the­o­ry behind the pop­u­lar blood type diet–which claims an individual’s nutri­tion­al needs vary by blood type–is not valid. The find­ings are pub­lished this week in PLoS One.

“Based on the data of 1,455 study par­tic­i­pants, we found no evi­dence to sup­port the ‘blood-type’ diet the­o­ry,” said the senior author of the study, Dr. Ahmed El-Sohe­my, Asso­ciate Pro­fes­sor and Cana­da Research Chair in Nutrige­nomics at the U of T.

“The way an indi­vid­ual responds to any one of these diets has absolute­ly noth­ing to do with their blood type and has every­thing to do with their abil­i­ty to stick to a sen­si­ble veg­e­tar­i­an or low-car­bo­hy­drate diet,” said El-Sohe­my.

Researchers found that the asso­ci­a­tions they observed between each of the four blood-type (A, B, AB, O) diets and the mark­ers of health are inde­pen­dent of the person’s blood type.

The ‘blood-type’ diet was pop­u­lar­ized in the book Eat Right for Your Type, writ­ten by natur­opath Peter D’Adamo. The the­o­ry behind the diet is that the ABO blood type should match the dietary habits of our ances­tors and peo­ple with dif­fer­ent blood types process food dif­fer­ent­ly. Accord­ing to the the­o­ry, indi­vid­u­als adher­ing to a diet spe­cif­ic to one’s blood type can improve health and decrease risk of chron­ic ill­ness such as car­dio­vas­cu­lar dis­ease. The book was a New York Times best-sell­er that has been trans­lat­ed into 52 lan­guages and sold over 7 mil­lion copies.

The U of T researchers took an exist­ing pop­u­la­tion of most­ly young and healthy adults who pro­vid­ed detailed infor­ma­tion about their usu­al diets and pro­vid­ed fast­ing blood that was used to iso­late DNA to deter­mine their ABO blood type and the lev­el of car­diometa­bol­ic risk fac­tors, such as insulin, cho­les­terol and triglyc­erides. Diet scores were cal­cu­lat­ed based on the food items list­ed in Eat Right for Your Type to deter­mine rel­a­tive adher­ence to each of the four ‘blood-type’ diets.

El-Sohe­my says that a pre­vi­ous lack of sci­en­tif­ic evi­dence doesn’t mean the diets didn’t work. “There was just no evi­dence, one way or the oth­er. It was an intrigu­ing hypoth­e­sis so we felt we should put it to the test. We can now be con­fi­dent in say­ing that the blood type diet hypoth­e­sis is false.” Last year, a com­pre­hen­sive review pub­lished in the Amer­i­can Jour­nal of Clin­i­cal Nutri­tion found no evi­dence to sup­port the ‘blood-type’ diet and called for prop­er­ly designed sci­en­tif­ic stud­ies to address it.

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For more infor­ma­tion, con­tact:

Ahmed El-Sohe­my
Depart­ment of Nutri­tion­al Sci­ences
Uni­ver­si­ty of Toron­to
Tel: 416–946-5776

Media Rela­tions
Uni­ver­si­ty of Toron­to
Tel: 416–978-0100