Diet Review: Blood Type Diet

June 13, 2017

Diet Review: Blood Type Diet


I sometimes find myself astonished at the new diets that clients bring to me. “Jess, what about _____? Or_____?”.  Most of the time I have already heard and researched about the diet so I can answer questions they may have. Other times, however, I’m like “huh? What is that?”. Not due to a lack of keeping up, but because there are new diets being invented without evidence based nutrition.


So, let’s dive into this “Blood Type Diet” a little. I am not going to lie, when I heard about this diet I think my eyes rolled so hard they almost fell into the back of my head. So, I went to the webpage where the founder (Dr. Peter D'Adamo, naturopathic doctor) of this diet presents the information.


Let’s start off with understanding what the Blood Type Diet actually is. The blood type diet is exactly what it sounds like - you eat according to your blood type. I have literally copied and pasted from the website how the different diet types are described:


The Diet Types


Type A: “…flourish on a vegetarian diet - if you are accustomed to eating meat, you will lose weight and have more energy once you eliminate the toxic foods from your diet. Many people find it difficult to move away from the typical meat and potato fare to soy proteins, grains and vegetables. But it is particularly important for sensitive Type As to eat their foods in as natural a state as possible: pure, fresh and organic.”


Type B: “…biggest factors in weight gain are corn, wheat, buckwheat, lentils, tomatoes, peanuts and sesame seeds. Each of these foods affect the efficiency of your metabolic process, resulting in fatigue, fluid retention, and hypoglycemia - a severe drop in blood sugar after eating a meal. When you eliminate these foods and begin eating a diet that is right for your type, you blood sugar levels should remain normal after meals. Another very common food that Type Bs should avoid is chicken. Chicken contains a Blood Type B agglutinating lectin in its muscle tissue….”


Type O: “…This blood type has a very well-developed ability to digest meals that contain both protein and fat. This is because two chemicals used by the digestive tract, an enzyme called intestinal alkaline phosphatase, and a lipoprotein called ApoB48 are secreted into the digestive tract in much higher amounts by type O's.”


Type AB: “…should avoid caffeine and alcohol, especially when you’re in stressful situations. Dr. D’Adamo recommends that Type AB focus on foods such as tofu, seafood, dairy and green vegetables if you are trying to lose weight. “Avoid all smoked or cured meats. These foods can cause stomach cancer in people with low levels of stomach acid,” recommends Dr. D’Adamo.”


Wait a second, Type A should eat more fresh and organic food? Wow, how enlightening! – wait… shouldn’t we all? Type B should avoid certain foods because of hypoglycemia? I dabbled into finding research that supports this and I drew a blank, I invite you to share some solid research that says otherwise. Type AB should avoid caffeine and alcohol in stressful situations – again, that is a nobrainer and I would recommend this to ANYONE.  Avoiding smoked or cured meats - that is straight up unhealthy. Period.




One of the backbones of the Blood Type Diet has to do with lectins. Lectins are carbohydrate-binding proteins, macromolecules that are highly specific for sugar molecules. The diet claims that different blood types will be affected by different lectin molecules and thus red blood cells will cluster together (sounds scary, I know).


While we know that certain diseases such as pancreatic cancer, thromboembolism, myocardial infarction and coronary atherosclerosis have been linked to an ABO blood type, we cannot start playing “connect the dot” with assumptions that a diet that is lower in “xyz” lectins will reduce the prevalence of a certain disease in that blood type.


So here is the question: have there been studies (and I mean good, solid, clinical trial, the gold standard) done to show that the ingestion of lectin containing foods specific to a blood type will either increase or decrease the agglunating effect that is claimed by the blood type diet? … (drumroll please)….. NO ( well, maybe in a small percentage of raw uncooked legumes, but that’s about it.). And furthermore, can we correlate some lectin-containing foods to affect blood types differently ? Research needs to be done!


My thoughts


So, here is my conclusion that about this diet that I will share with you. If you have heard of promising results from people, guess what – it is probably due to the individual having a poor diet before this diet, moving to a healthier diet- not due to the “science” behind the diet itself. I would argue to say that any blood type would find improvements in any of these diets if it were generally healthier than what they were already practicing. There is not enough sound research conducted to this day to support that a diet designed around blood types can resolve the claims that have been made.


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