The Blood Type Diet - Myths & Facts
This diet was created by a naturopathic physician named Peter J. D’Adamo. He wrote a book in 1996 entitled ‘Eat Right for Your Type’, this book has sold over 7 million copies to date and made the New York Times bestseller list.
Usually when I write this type of blog that looks at different diets, I try to stay open minded. My personal belief is that restricting yourself to a certain diet for whatever reason is not necessary. Eating a balanced diet, only removing foods that you know you are allergic or intolerant to (i.e. you have been tested and the test result show this), allowing yourself to enjoy the food you love while being aware of your portion sizes, staying active and looking after your mental health is all you have to do!
However,when researching this diet…I have never seen a bigger con in all my life! So, if you are a firm believer in the blood type diet a fair bit of warning, this blog should make you rethink a few things.
First let’s look at the theory behind the Blood Type Diet which is that your blood type reveals the dietary habits of our ancestors and will determine what kind of food we should eat, what supplements we should take and even what type of exercise we should do to maintain a healthy weight and reduce our risk of developing chronic diseases. D’Adamo claims that foods react chemically with your blood type. So following the diet best suited to your blood type will help you digest food more efficiently, have more energy and be at lower risk of developing diseases (Watson, 2016).
There are two main classification systems for blood types. The ABO system has four types. Type A, type B, type AB and type O. The Rhesus system and blood types are classified as Rhesus positive or Rhesus negative (e.g. type A+ or Type A-). Blood group classification was one of the first recognizable genetic variants in humans. So, you will have the same blood type as either your biological mother or father. There have also been studies that show your blood type can be associated with your risk of developing Cancer, Malaria, cholera or cardiometabolic diseases (Liumbruno and Franchini, 2013). This is what D’Adamo formed his hypothesis surrounding blood types, diet, and exercise on. A hypothesis is basically a set of observations that haven’t yet been proven. He proposed that that certain sugar binding protein components in foods called lecithin bind with the antigens on the blood cells and this may lead to agglutination (clumping together of blood cells) and disease.
So, what can you eat on this diet? It depends on your blood type.
Blood type A diet is a mostly a vegetarian diet, high in carbohydrates and low in fats. Plenty of fruits & vegetables, ideally fresh and organic Animal products (meat, poultry, fish, eggs, dairy).
Blood type B diet is high in protein, low in carbohydrates. Green vegetables, eggs, certain meats, and low-fat dairy. Corn, wheat, buckwheat, lentils, tomatoes, peanuts, sesame seeds and for some reason chicken is ‘problematic’ (D’Adamo’s words not mine!).
Blood type AB diet includes tofu, seafood, dairy, and green vegetables Caffeine, smoked/cured meat, and alcohol.
Blood type O diet includes lean meat, poultry, fish, and vegetables, and light on grains, beans, and dairy Wheat and most other grains
If you’ve read some of my earlier blogs looking at Low Carb Diets Atkins and Keto and the Paleo/Hunter gatherer Diet. The recommendations for blood type B and type O closely resemble them. One thing all the blood type diets have in common is cutting out processed food and that HAS got scientific evidence backing it’s beneficial effects on weight and overall health, but none of this evidence states that your blood type dictates which diet would work best for you.
The Blood type diet also tells you which type of exercise you should be doing in order to stay healthy, depending on your blood type.
• Type B – moderate swimming or walking
• Type O – vigorous aerobic exercise such as jogging or cycling for up to an hour every day!
I don’t know about you, but I wouldn’t like to be type O!
A major red flag for me when it comes to recognising a ‘fad diet’ or ‘bad’ dietary advice is when there’s no scientific evidence to back the claims. In 2013 there was a systematic review carried out on 1000 scientific papers looking at whether blood type influences what we should be eating (Cusack et al., 2013). They found no evidence at all supporting the claim that blood type has anything to do with what diet a person should follow for optimal health. Ten years before this systematic review (in 2003) The Norwegian medical Association released numerous scientific papers in which researchers tried to determine whether there was any truth to this claim as at this point over 40,000 copies of the book ‘Eat Right for Your Type’ had been sold in Norway. They also concluded that the claim was utter “Nonsense” (Greger, 2015).
Now you’d think by now the Dr Peter J. D’Adamo would have something to say? Well he did. In fact he said quote “there is good science behind the blood type diet, just like there was good science behind Einstein’s mathematical calculations” (Greger, 2015). Basically, he’s saying that if the Blood Type theory was tested, he would be proved right. He claims there is no available money to fund the trials. He has sold over 7 million copies of his book worldwide, if he really believed that proper scientific testing would show the world his theory is correct why can’t he fund his own research like the Atkins foundation did?
Back in 1996 he when his book was released, he did claim to be in the eighth year of a ten year clinical trial, meaning the results should have been available in 1998…twenty-three years later and still no sign of them.
As well as selling the book he also has his own line of supplements which he recommends for anyone who wants to follow the Blood Type Diet (another red flag for a ‘fad diet’ is selling expensive supplements that cannot be found elsewhere and the you ‘must have’ to be successful in the particular diet). He also recommends a lot of speciality and organic foods that can be pricey.
The big question is, does it work. The answer is complicated. The different diets do have different health benefits that have been proven. For example, the Type A diet is mainly plant based and we know a plant-based diet has many health benefits especially your cardiometabolic health. The Type AB diet is also rich in plant-based foods and has been linked to favourable health benefits. Even though it does contain some animal proteins including fish, eggs, and dairy. The Type O diet has been associated with reduced triglycerides. However, there is absolutely no evidence showing that your blood type has any effect at all o which of these diets would work for you.
Cusack, L., De Buck, E., Compernolle, V. and Vandekerckhove, P. (2013) Blood type diets lack supporting evidence: a systematic review. The American Journal of Clinical Nutrition, 98(1) 99–104.
Liumbruno, G.M. and Franchini, M. (2013) Beyond immunohaematology: the role of the ABO blood group in human diseases. Blood Transfusion, 11(4) 491–499. Available from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3827391/ [accessed 29 March 2021].
Watson, S. (2016) Blood Type Diet: Eating for Types O, A, B, & AB Available from https://www.webmd.com/diet/a-z/blood-type-diet [accessed 29 March 2021].