Which Blood Group Doesn't Eat Beans? Exploring the Blood Type Diet

December 9, 2025 •

3 min read

Created by naturopath Peter D'Adamo, the blood type diet suggests that people with type O blood should avoid or limit beans and other legumes. This theory is controversial, and major scientific bodies have found no evidence to support its central claims.

Quick Summary

The blood type diet, developed by Peter D'Adamo, recommends that people with blood type O restrict their intake of beans and legumes. Modern scientific evidence, however, does not support this dietary premise or its purported benefits.

Key Points

Blood Type Diet Theory: According to the unproven blood type diet, individuals with type O blood should avoid or limit beans and other legumes.
No Scientific Support: A systematic review published in the American Journal of Clinical Nutrition found no scientific evidence to validate the health benefits claimed by the blood type diet.
Lectin Claims Debunked: The theory that lectins in beans negatively affect certain blood types is not supported, as cooking typically neutralizes these proteins.
Benefits of Beans: From a mainstream nutrition perspective, beans are a nutrient-rich food, providing fiber, protein, and essential nutrients, and are beneficial for most people regardless of blood type.
Healthier Approach: Health experts recommend a balanced diet based on established nutritional science rather than restrictive and unproven theories like the blood type diet.
Universal Health Benefits: Any improvements in health reported by followers of the blood type diet are likely due to the general shift toward healthier, less-processed foods, a benefit not exclusive to any single blood type.

Understanding the Blood Type Diet

In his popular 1996 book, Eat Right 4 Your Type, naturopath Peter D'Adamo introduced the idea that a person's diet should be based on their ABO blood type. The theory is predicated on the idea that each blood type has specific ancestral origins and that certain food proteins, called lectins, can adversely react with the blood antigens of different blood types. For individuals with type O blood, which D'Adamo associates with 'hunter-gatherer' ancestors, a high-protein diet with red meat is recommended, while many grains and legumes are discouraged.

The Claim Against Beans for Type O

According to this specific dietary theory, people with blood type O are advised to avoid or significantly limit their consumption of beans and other legumes. Specific beans often cited include: kidney beans, navy beans, and lentils. D'Adamo's reasoning centers on the idea that the lectins in these foods can cause issues like weight gain, digestive troubles, and inflammation for type O individuals. The premise suggests that eating foods with incompatible lectins causes blood cells to clump together (agglutination) and that this is detrimental to health.

What Does Mainstream Science Say?

Despite the diet's popularity, especially among celebrities, the scientific and medical consensus is that the blood type diet is not supported by empirical evidence. A comprehensive 2013 systematic review published in the American Journal of Clinical Nutrition found no evidence to validate the health benefits of blood type diets. A subsequent 2014 study confirmed that any health improvements observed by followers were independent of their blood type. These improvements were likely the result of adopting generally healthier eating habits, such as reducing processed foods and increasing fruits and vegetables, which many of the diet's recommendations encourage.

The Role of Lectins in Diet

Lectins are indeed present in many plant foods, including beans. However, the vast majority of dietary lectins are destroyed during the cooking process, and the body also has defense mechanisms to handle them. Only specific, raw lectins are known to be harmful. The notion that lectins from cooked beans specifically and negatively interact with certain blood types lacks scientific backing. For the general population, the health benefits of consuming beans—which are rich in fiber, plant-based protein, and micronutrients—far outweigh any theoretical risks posed by lectins. Legumes are a staple of many nutritious, balanced diets worldwide.

Comparison of Blood Type Diet Claims vs. Scientific Consensus


Feature	Blood Type Diet Claims	Scientific Consensus
Basis for Recommendations	Ancestral diet and specific lectin-blood type reactions.	Based on nutritional evidence, not blood type.
Type O and Beans	Avoids beans (e.g., kidney, navy) and other legumes due to lectins.	No evidence suggests people with type O blood should avoid beans.
Scientific Evidence	Purported benefits for health and weight loss.	Lacks empirical support; benefits are linked to overall healthy habits, not blood type.
Lectin Concerns	Emphasizes lectin incompatibility with specific blood types.	Most dietary lectins are rendered harmless by cooking; specificity claims are unproven.
Dietary Balance	Restrictive diets excluding entire food groups, like dairy or grains.	Promotes a balanced intake from all food groups for balanced nutrition.

Conclusion: Rely on Evidence-Based Nutrition

In summary, while the popular blood type diet theory asserts that people with type O blood should not eat beans, this claim is not supported by credible scientific evidence. Most health experts, including dietitians and physicians, consider the blood type diet a fad and instead recommend a balanced, varied diet rich in whole foods, regardless of one's blood group. Beans and legumes are a valuable part of a healthy diet for virtually everyone. Instead of restricting food based on unproven theories, individuals concerned about their diet should consult with a healthcare professional or a registered dietitian for personalized, evidence-based nutritional advice.

Blood Type Diet Information

Peter D'Adamo Official Website: www.dadamo.com

Beyond the Blood Type Diet

Focusing on balanced nutrition is more productive than adhering to restrictive, unproven diets. A healthy diet typically includes a wide variety of vegetables, fruits, whole grains, and lean proteins, and for most people, this includes beans. Rather than fixating on the pseudoscientific connection between blood type and food, individuals can achieve better health outcomes by eating a balanced diet, incorporating regular exercise, and making sustainable lifestyle changes.

Frequently Asked Questions

No, there is no scientific evidence to support this claim. It is a central tenet of the unproven blood type diet, which lacks validation from major health organizations and scientific research.

Proponents of the diet claim that specific proteins in beans called lectins can be incompatible with the blood antigens of type O individuals, causing agglutination (blood cell clumping) and other health issues.

While lectins are present in many plants, cooking typically destroys most harmful types. The theory that specific lectins in cooked beans are harmful to certain blood types has not been scientifically proven.

According to the blood type diet theory, type O individuals should avoid or limit kidney beans, navy beans, and lentils, among other legumes.

Any health improvements are likely due to the diet's general recommendations for reducing processed foods and increasing whole foods, not from adhering to blood type-specific rules. These benefits would apply to anyone, regardless of their blood type.

The medical and scientific consensus is that the blood type diet is a fad diet. Multiple reviews have found no evidence to support its foundational theories or health claims.

Most health experts recommend basing your dietary choices on established nutritional science, which promotes a balanced intake of diverse foods, rather than a restrictive plan based on an unproven theory like the blood type diet.