Bananas are not considered bad for people with AB blood type, even within the Blood Type Diet that popularized this idea. The diet, created by naturopath Peter D’Adamo, actually classifies bananas as “highly beneficial” for both type B and type AB individuals. Type A is the group told to avoid bananas. So the premise behind this search appears to be based on a misattribution, but the bigger question is whether any of these blood-type food rules hold up to scientific testing. They don’t.
What the Blood Type Diet Actually Says
The Blood Type Diet assigns foods to categories of “highly beneficial,” “neutral,” or “avoid” based on your ABO blood group. The theory is that proteins called lectins in certain foods react differently with blood type antigens, potentially causing digestive problems or other health issues. For bananas specifically, the diet lists them as highly beneficial for types B and AB, neutral for type O, and something type A individuals should avoid because they supposedly interfere with digestion.
If you’ve seen claims online that AB types should skip bananas, the information was likely confused with the type A recommendation, or mixed up with other fruits the diet does restrict for AB individuals. The diet does tell AB types to avoid certain tropical fruits like mangoes, guava, and coconuts, which may be the source of the confusion.
The Lectin Theory Behind It All
D’Adamo’s central argument is that lectins, a type of protein found in many plant foods, interact with the sugar molecules on the surface of your blood cells in ways that depend on your blood type. Eating the “wrong” lectins for your type supposedly triggers clumping of blood cells, inflammation, and poor digestion. This is the reasoning behind every food recommendation in the diet, including the ones about bananas for type A.
Lectins are real compounds, and in large enough quantities (particularly from raw kidney beans), they can cause genuine digestive distress. But the leap from that fact to the idea that banana lectins selectively harm people based on blood type has no supporting evidence. Cooking, soaking, and even normal ripening reduce lectin activity substantially. As researchers at MD Anderson Cancer Center have noted, boiling, baking, pressure cooking, and soaking all deactivate lectins so they no longer have the same biological effect. Even removing peels and seeds reduces active lectin content. The tiny amount of lectin in a ripe banana is not a credible threat to anyone’s digestion regardless of blood type.
What the Science Says About Blood Type Diets
Two major studies have directly examined whether eating according to your blood type produces any measurable health benefit. Neither supports the theory.
A 2013 systematic review published in the American Journal of Clinical Nutrition searched through 1,415 references looking for evidence that blood type diets improve health. Out of all that research, only one study even came close to being relevant, and it examined a different blood group system (MNS, not ABO) in response to a low-fat diet. The reviewers concluded that no evidence exists to validate the health benefits of blood type diets.
A year later, researchers at the University of Toronto took a more hands-on approach. They enrolled 1,455 participants and measured how closely each person’s eating habits matched the dietary recommendations for each blood type. They then checked a range of health markers: BMI, waist circumference, blood pressure, cholesterol, triglycerides, and insulin levels. People who followed the type A diet pattern did show improvements in several of these markers. People following the type AB diet pattern also showed some improvements, particularly in cholesterol, triglycerides, and blood pressure. But here’s the key finding: these benefits had nothing to do with the person’s actual blood type. A type O person eating the “type A diet” got the same results as a type A person eating it. The improvements came from the overall quality of the diet, not from any blood-type-specific mechanism.
This makes sense when you look at what these diets actually recommend. The type A and AB diets emphasize fruits, vegetables, and whole grains while limiting processed food. That pattern improves health markers for virtually everyone, regardless of what antigens sit on their red blood cells.
Should You Eat Bananas?
Bananas are a good source of potassium, vitamin B6, and fiber. A medium banana contains about 3 grams of fiber, 422 milligrams of potassium, and roughly 105 calories. There is no physiological reason for someone with AB blood to avoid them, and the Blood Type Diet itself doesn’t suggest they should.
The only people who genuinely need to limit bananas are those with kidney disease who must restrict potassium intake, people with a rare banana allergy (sometimes linked to latex allergy), or individuals managing blood sugar carefully who prefer lower-sugar fruit options. None of these situations have anything to do with ABO blood type.
If you’ve been avoiding bananas because of something you read about blood types, you can add them back without concern. The entire framework connecting specific foods to blood type compatibility lacks scientific support, and in this particular case, even the diet’s own creator would tell you bananas are fine for AB.