The Blood Type Diet, developed by Peter D’Adamo, suggests that an individual’s ABO blood type determines the healthiest diet. This framework proposes that different blood types process foods and nutrients differently, with specific foods acting as either beneficial or harmful based on their interaction with blood antigens. For Blood Type O individuals, a distinct set of dietary recommendations exists, focusing on ancestral eating patterns for the first meal of the day.
The Hunter-Gatherer Foundation
Proponents of this dietary theory categorize Blood Type O as the “Hunter,” suggesting it is the oldest blood type, tracing back to early human hunter-gatherers. This ancestral connection is the theoretical basis for a diet high in protein from lean meats. The theory suggests that the Type O digestive system is well-suited to process animal protein and fat, partly due to naturally higher levels of stomach acid compared to other blood types.
This “Hunter” profile translates into a diet that prioritizes muscle-building protein while recommending the reduction of grains and legumes. The rationale is that these items were not a significant part of the hunter-gatherer diet and contain lectins, which are theorized to negatively interact with Type O antigens, potentially causing inflammation or digestive issues. This foundational belief system directly shapes the composition of a recommended Type O breakfast.
Specific Breakfast Recommendations for Type O
Breakfast for a Type O individual should center on protein and beneficial vegetables to align with the proposed ancestral eating pattern. Lean animal proteins are considered highly beneficial, such as grass-fed beef, lamb, or venison, although these are often impractical for a typical breakfast. A more common approach involves eggs, which are generally acceptable in small amounts, perhaps poached or scrambled.
Pairing the protein source with beneficial vegetables like kale, spinach, or collard greens is encouraged, often prepared in an omelet or scramble. Healthy fats, particularly olive oil, are recommended for cooking and dressing, as they are believed to support cholesterol metabolism.
The diet recommends limiting or avoiding common breakfast staples like wheat-based toast, bagels, and most forms of oatmeal, which contain gluten and lectins problematic for Type O individuals. Alternatives like sprouted-grain bread, such as Essene bread, are suggested as a neutral option in very small quantities. Beneficial fruit choices include figs, prunes, and dark berries, while common fruits like oranges and strawberries should be avoided.
Beverages also follow specific rules; coffee is generally discouraged because it can increase adrenaline and noradrenaline, which the theory suggests are already high in Type O individuals. Green tea is recommended as a better morning alternative. Dairy products, including milk, yogurt, and most cheeses, are advised to be severely restricted due to potential digestive intolerance, leaving soy milk as one of the few neutral dairy alternatives.
Expert Commentary on Diet Validity
While the Blood Type Diet offers detailed recommendations, mainstream nutritional science does not support its foundational premise. A systematic review of the scientific literature found no evidence to validate the purported health benefits of diets based on the ABO blood group system. The theory that blood type determines specific dietary needs is not supported by clinical evidence or major medical organizations.
Studies examining the diet have found no significant interaction between a person’s blood type and the results of following the corresponding blood type diet. In one analysis of over a thousand participants, adherence to a Type A diet, which is high in fruits and vegetables, was associated with better health markers across all blood types. Any perceived health improvements from following the Type O diet are most likely due to the general shift toward whole, unprocessed foods and the reduction of refined carbohydrates. The diet encourages lean protein and a variety of vegetables, which are components of many scientifically supported healthy eating patterns.