What Should Blood Group B Avoid? Separating Fact from Fiction

January 11, 2026 •

4 min read

First popularized in the 1990s, the blood type diet suggests that individuals should eat based on their blood type. For those asking what should blood group B avoid, the diet proposes a specific list of foods, though a comprehensive review found no scientific evidence to support this approach.

Quick Summary

The blood type diet suggests specific foods for type B individuals to avoid, like chicken and wheat, based on ancestral theories. However, overwhelming scientific evidence refutes this dietary approach, highlighting that any benefits are likely from healthier eating, not blood type.

Key Points

Blood Type Diet is Unproven: There is no scientific evidence to support the claims that certain foods are bad for Blood Group B based on blood type.
Specific Foods to 'Avoid': The diet suggests Type B individuals should avoid chicken, corn, wheat, lentils, peanuts, and tomatoes due to proposed lectin incompatibilities.
Lectins are Misrepresented: The diet's theory about harmful, blood-type-specific lectins is scientifically baseless, as cooking typically destroys lectins and most aren't blood-type specific.
Health Benefits are General: Any health improvements experienced on the diet are likely due to cutting out processed foods and eating healthier, not adhering to blood type rules.
Consult a Professional: For personalized dietary advice, it is best to speak with a healthcare provider or registered dietitian rather than following an unproven diet.

Understanding the Blood Type Diet Theory

The concept of tailoring a diet to one's blood type was introduced by naturopath Peter D'Adamo in his 1996 book, Eat Right 4 Your Type. The theory is based on the idea that blood types evolved at different times in human history and that certain foods, especially those containing proteins called lectins, can be harmful if they don't match an individual's blood type. For Blood Type B individuals, whose ancestors were supposedly nomadic, the diet suggests avoiding specific items believed to interfere with metabolism and immune function.

Foods the Blood Type Diet Recommends Avoiding for Type B

According to the Blood Type Diet, Type B individuals should avoid the following food groups to optimize their health and prevent potential issues like fatigue, fluid retention, and metabolic slowdowns:

Meats & Poultry

Chicken and chicken broth
Pork, including bacon, ham, and sausage
Goose, duck, and quail
Specific seafood like anchovies, octopus, and most shellfish

Grains & Legumes

Wheat (all products)
Corn (all forms)
Buckwheat
Lentils
Rye and soba noodles
Peanuts and peanut butter
Black-eyed peas and pinto beans

Nuts & Seeds

Sesame seeds and sesame oil
Pumpkin seeds
Sunflower seeds
Cashews and pistachios

Fruits & Vegetables

Tomatoes (all forms)
Avocados and coconuts
Pomegranates and rhubarb
Olives and artichokes

Dairy Products

American cheese, string cheese, and blue cheese
Ice cream

Other

Soy products like tofu and soy oil
Carbonated beverages

The Overwhelming Scientific Consensus

Despite the specific recommendations, the Blood Type Diet has been widely debunked by the scientific and medical communities. A landmark 2013 systematic review in the American Journal of Clinical Nutrition found no evidence to support the diet's claims. Subsequent studies, including a 2018 review involving overweight adults, similarly concluded that ABO genotype does not modify the effectiveness of a diet.

Medical experts and nutritionists dismiss the diet's central premises as pseudoscience. The idea that lectins selectively harm certain blood types is largely unfounded; most lectins are destroyed by cooking, and the few that remain don't react in a blood-type-specific manner. The ancestral theory is also scientifically questionable. The reason people may experience health benefits on this diet is not due to their blood type, but rather because the plan encourages a healthier lifestyle by eliminating processed foods and promoting increased fruit and vegetable intake.

Potential Risks of Following the Blood Type Diet

Adopting a diet with severe restrictions can pose several risks:

Nutrient Deficiencies: Cutting out entire food groups can lead to deficiencies. For example, if someone with Type B blood is lactose intolerant and also avoids chicken and lentils per the diet, they may lack key protein sources and nutrients.
Unnecessary Restriction: Eliminating healthy, nutrient-dense foods like tomatoes, which are rich in antioxidants, has no scientific basis and is unnecessarily restrictive.
Lack of Evidence-Based Results: Since the diet lacks scientific support, there is no guarantee it will achieve the promised health improvements. Following an evidence-based approach is always safer and more effective.
Mental Toll: The strict limitations can make meal planning difficult and create stress, which is counterproductive to overall health.

Blood Type Diet Claims vs. Scientific Reality


Feature	Blood Type Diet Claim (for Type B)	Scientific Consensus	Why the Difference?
Dietary Restrictions	Restrict certain foods like chicken, corn, and wheat.	No specific dietary restrictions based on blood type are needed for health.	The theory lacks scientific evidence; studies show no correlation.
Underlying Mechanism	Lectins in incompatible foods cause blood cell clumping.	Most lectins are neutralized by cooking and aren't blood-type specific.	The foundational theory is flawed and not supported by research.
Health Improvements	Boosted metabolism, improved energy, reduced disease risk.	Any health benefits are likely from eating more whole foods and less processed junk.	The diet's positive effects come from its general healthy eating advice, not the blood type alignment.
Weight Loss	Automatic weight loss from eating 'right for your type'.	Weight loss occurs from caloric reduction, often due to the diet's restrictive nature.	The underlying mechanism for weight change is not linked to blood type.

Conclusion

While the Blood Type Diet presents specific recommendations for what blood group B should avoid, these claims are not supported by credible scientific evidence. Extensive research and expert consensus indicate that a person's blood type has no impact on their dietary needs. Instead of adhering to restrictive and unproven rules, individuals should focus on a balanced, whole-food diet rich in a variety of fruits, vegetables, lean proteins, and healthy fats. For truly personalized nutrition advice, consulting a registered dietitian is the most effective and evidence-based approach. The benefits often attributed to the blood type diet are simply the result of adopting generally healthier eating habits.

For more information on the lack of scientific backing for the blood type diet, consult this review from Healthline.

Frequently Asked Questions

No, scientific research has found no evidence that your blood type should determine your diet. The theory that certain foods are incompatible with specific blood types is widely dismissed by health experts.

According to the diet's originator, Peter D'Adamo, chicken contains a lectin that supposedly agglutinates (clumps) the blood of Type B individuals, but this has not been scientifically validated.

If you lose weight on the blood type diet, it is most likely because the restrictive nature of the plan forces you to eliminate high-calorie processed foods. Weight loss is a function of overall calorie balance, not blood type.

Yes, following the diet's restrictions can be unnecessarily difficult and could potentially lead to nutritional deficiencies by cutting out healthy foods without a valid reason. It's a highly restrictive diet without scientific justification.

For optimal health, Blood Group B individuals, like everyone else, should focus on a balanced diet of whole foods, including fruits, vegetables, lean proteins, and healthy fats. Personal dietary needs should be guided by a doctor or dietitian.

Yes, it is safe to eat tomatoes and corn. The claim that these foods negatively affect Type B individuals is part of the scientifically debunked blood type diet theory. These are nutritious foods for most people.

For reliable, personalized dietary advice, you should consult a qualified medical professional, such as a registered dietitian or your doctor, who can take into account your entire medical history and current health status.