From the archives: A few years back, the Blood Type Diet was all the fad, and it’s still mentioned in passing occasionally. In this article from 2018, nutritionist Jennifer Bowden looked at whether there was any validity to it. Most recent reports say there is remains no science to support it.
Question: My friend follows the blood type diet. She has an O blood type, and as such eats meat, but less dairy and wheat for better health. She believes many others might benefit from this diet. Is there any real science behind it, or is it just a fad?
Answer: There is no one alive who is You-er than You, wrote Dr Seuss. And indeed, you are genetically unique – so should your diet be unique, too?
American naturopath Peter J D’Adamo contends that as ABO blood type is associated with our risk of certain health conditions, we should tailor our diet to our blood type. In his book Eat Right for Your Type, originally published in 1996, D’Adamo outlines diets for each blood type aimed at improving health and reducing the risk of chronic diseases such as cardiovascular disease.
D’Adamo’s theory is that those with group O blood type would thrive on a diet that resembles the high animal protein diet typical of certain groups in the hunter-gatherer era, as group O is considered the ancestral blood group in humans. Whereas those with group A would thrive on a vegetarian diet, as theoretically this blood group evolved when humans began cultivating land. While group B theoretically originated in nomadic tribes, so they would benefit from dairy products. Finally, the AB blood group is lumped with a diet midway between that of group A and group B.
So, what do we know about D’Adamo’s claims?
Certainly, some of D’Adamo’s nutrition recommendations, irrespective of blood type, fit with current nutrition advice. Such as advising those with group A blood to “limit sugar, caffeine and alcohol”.
What’s more, there is considerable evidence that blood type is linked to disease risk. For example, those with blood group O have been found to have a reduced risk of deep vein thrombosis. While group B individuals have a lower risk of type 2 diabetes compared with group O.
In 2010, researchers noted that those with blood group A had an increased risk of gastric cancer, while peptic ulcer risk was highest among those with blood group O. And in 2017, a study following more than 18,000 Chinese men found people with blood type B had a statistically lower risk of all cancers, compared with blood type A. This suggests that genetic traits linked to our blood type may play a role in the development of cancers in the gastrointestinal and urinal tracts.
Interestingly, in 2012, researchers noted that blood type seemed to modulate the composition of our all-important gut microbiota.
Still, this doesn’t answer the question: does a blood type diet uniquely benefit our health?
To get to the bottom of this, researchers at the University of Toronto analysed data from 1455 participants in the Toronto Nutrigenomics and Health study. They assessed their dietary intake and used a diet score to calculate the similarity of their diet to each of the four “Blood-Type” diets. Their ABO blood group and cardiometabolic health were also tested.
Their findings, published in 2014 in the PLoS One journal, revealed that irrespective of blood group type, those whose diet was most similar to the Type-A diet had a lower BMI, waist circumference, blood pressure, serum cholesterol, triglycerides, and measures of insulin resistance; those who stuck to a Type-AB style diet also had lower levels of these biomarkers, with the exception of their BMI and waist circumference; those adhering to a Type-O style diet had only lower triglycerides; while no significant effects were linked to the Type-B style diet.
However, when they analysed the participants’ results based on their adherence to the diet specifically for their blood type, there was no greater effect on these biomarkers.
In summary, then, they found certain blood-type diets are linked to a reduction in cardiometabolic risk factors, but this was completely independent of the individual’s blood type.
So, if you’re following the Type-A or Type-AB diet, you might expect to have better health, but that likely has nothing to do with your blood type and everything to do with the fact you’re eating a healthier diet.
This article was originally published in the NZ Listener, June 2 – 8, 2018.
