They are a fad that refuses to fade, but no solid evidence
exists to show whether or not eating plans tailored to ABO blood types promote
health, say Belgian researchers, who tried their best to find some.
After sifting through the scientific literature, researchers
identified just one indirectly related study - it looked at the effects of
low-fat diets on cholesterol levels in people with different blood types - and
even that one was weak, they concluded.
Some studies have found links between blood type and risk
for developing blood clots or certain cancers, of having a heart attack and of
haemorrhaging when infected with Dengue fever. But no peer-reviewed research has
indicated that eating foods supposedly compatible with one's blood type will
improve health or induce weight loss more than a general diet plan.
Medical professionals already knew this, according to the
study's senior author, Dr Philippe Vandekerckhove at the Belgian Red
Cross-Flanders in Mechelen."However, the general populace have access to
blood type diets, regardless of medical guidance, and cannot be expected to be
able to determine whether or not the health claims are, in fact,
'evidence-based'," Vandekerckhove said.
Blood type is determined by proteins on the surface of red
blood cells and antibodies in the blood. The most familiar grouping, known as
ABO blood types, refers to whether a person's cells carry the proteins known as
A or B, or both of them, or neither of the two - which is designated blood type
O. The idea that blood type influences an individual's life - and even
personality - is popular in parts of Asia. In 2011, for example, a Japanese
politician apologised for a rude remark he had made about tsunami victims by
blaming his blood type.
Your diet and diet
But blood type eating
regimens are often premised on the theory that blood group signals a
population's evolutionary background - primarily agrarian or hunter-gatherer,
for instance - and that ancient history inclines people of certain blood types
to thrive or suffer when eating one kind of diet or another.
Vandekerckhove's team, who published their results in The
American Journal of Clinical Nutrition, searched the largest online databases
of published research for clinical trials, reviews and all other types of
studies for reports about people grouped by blood type following specifically
Of 1 415 articles that initially turned up in the search, 16
looked promising at the start but 15 of those were discarded on closer analysis
when the authors saw that they were poorly designed. Only one was relevant to
the topic and strong enough to be included in an analysis because it was a
randomized controlled trial.
But it had several other weaknesses, including the fact that
participants knew which group they had been assigned to, the group sizes were
small, and the main endpoint assessed was "bad cholesterol" levels,
which doesn't directly address the question of health or weight.
Experts studied participants’
diet and lifestyle
Vandekerckhove and his coauthors were surprised and
disappointed to find that no studies had been done that actually addressed the
question, he said."Until a study has been performed which recruits people
with a certain blood type who have adhered to the diet, compared with those of
the same blood type who have not adhered to the diet, and the incidence of
disease/measurement of health can be assessed, then the health effects of a
blood type diet are not proven," he wrotel.
"Currently, there is no evidence to support that 'Blood
Type Diets' have any effect on positively benefiting your health," said
Beth Warren, a registered dietician in New York City who was not involved in
"The fad diet was only made popular by a book during
1996...with no evidence to support it," Warren told Reuters Health."Eat
Right 4 Your Type" by Peter D'Adamo has more than 7 million copies in
print, and outlines a theory about which foods are best for people with the
various ABO blood types to eat and which to avoid. D'Adamo says he believes in
the diet based on circumstantial evidence.
"All the authors did was conclude, as have I, that
there is a lack of direct research on the subject," D'Adamo told Reuters
Health by email. He too would like to see direct research on the diets, but
such studies are unlikely because they would be too costly. One-size-fits-all
diets don't make sense either, D'Adamo said, and it may be that blood type is
one way to predict which general weight loss diets work better for which
"We hope the results of this systematic review will
reinforce the need for individuals and companies to take responsibility of
their claims and clearly differentiate between something that is
"evidence-based" rather than something that is
"theoretical"," Vandekerckhove said."We have to be very
careful when we hear of fad diets and look into if and how this way of eating
benefits our health and goals for weight-loss and maintenance," Warren
said. "In this case, we cannot say that it does at this time," she