The Blood Type Diet, popularized by naturopathic doctor Peter D’Adamo, asserts that an individual’s ideal nutrition should be determined by their specific ABO blood group. The theory suggests that the antigens defining the blood type influence how the body processes different foods. Following a diet tailored to one’s blood type is claimed to improve digestion, increase energy, and help prevent disease. This article examines the food recommendations and restrictions outlined in the Blood Type Diet for individuals with Blood Type O, including the common O+ subtype.
The Rationale for Blood Type O+ Dietary Needs
The theoretical framework for the Blood Type O diet is based on an evolutionary premise, suggesting that Type O is the oldest blood group, corresponding to the “Hunter” ancestor. This ancestry is claimed to have endowed Type O individuals with a digestive system better equipped to metabolize animal proteins due to higher stomach acid levels. This characteristic is why the diet emphasizes a high-protein intake.
The diet’s mechanism centers on lectins, which are proteins found in food that can bind to carbohydrate molecules on the surface of cells. The theory suggests that lectins in certain foods are incompatible with Type O blood antigens, leading to an agglutination, or clumping, effect. This incompatibility is linked to health issues such as inflammation, digestive problems, and metabolic disruption.
Eliminating foods containing incompatible lectins is suggested as the path to optimal health for Type O individuals. The diet proposes that Type O digestive systems are less suited for agricultural foods, such as grains and dairy products, which became prevalent later in human history. Therefore, the recommended plan strongly favors foods lower in problematic lectins while encouraging high intake of animal proteins.
Core Food Recommendations for Type O+
The dietary recommendations for Blood Type O+ are high in protein, resembling a paleo or low-carbohydrate approach. This plan strongly encourages the consumption of lean, high-quality animal proteins, considered beneficial for Type O individuals. Recommended meats include beef, lamb, mutton, and venison, which are thought to be easily digestible.
Seafood is also a cornerstone of the diet, particularly fish rich in omega-3 fatty acids. These include salmon, cod, mackerel, and herring, which are suggested to have anti-inflammatory properties that complement the Type O metabolism. These protein sources are believed to help stimulate high stomach acid levels, aiding in digestion.
Many vegetables are encouraged, focusing on dark, leafy greens like kale and spinach, along with broccoli, which are believed to support metabolism. Olive oil is the preferred fat source for cooking and dressing; linseed (flaxseed) oil is also listed as beneficial. Among nuts and seeds, pumpkin seeds and walnuts are specifically recommended.
The allowance for grains and legumes is minimal, though a few types are designated as acceptable or neutral. Acceptable legumes include pinto beans and black-eyed peas. Fruits such as figs, plums, and prunes are encouraged for their vitamins and fiber content.
Foods to Exclude or Restrict for Type O+
A significant part of the Blood Type O diet involves the severe restriction or complete avoidance of several major food groups. Grains and wheat products are heavily discouraged, as the diet claims the lectins in wheat interfere with metabolism and promote inflammation. This restriction covers nearly all common wheat forms, including whole wheat, bulgur, and durum, as well as corn.
Most dairy products are categorized as foods to avoid, based on the theory that Type O individuals often lack the necessary enzymes for proper digestion and metabolism. This restriction includes most milk, cheese (such as Cheddar, Swiss, and Brie), and yogurt. Some neutral options like goat cheese, mozzarella, and butter are listed, but with severe restriction, as dairy is suggested to cause digestive discomfort and weight gain.
Certain legumes and seeds are blacklisted for Type O, including kidney beans, lentils, and peanuts, which are thought to contain incompatible lectins. Specific vegetables are also advised against. These exclusions are based on the purported negative interactions between the foods’ lectins and the Type O blood antigen.
Excluded Foods
The diet advises against specific legumes, seeds, and vegetables:
- Kidney beans
- Lentils
- Peanuts
- Potatoes
- Eggplant
- Certain mushrooms
Beverage restrictions include avoiding coffee, black tea, and distilled liquor, as these are suggested to negatively affect the digestive tract. The diet recommends replacing these with water, herbal teas, and approved fruit juices like pineapple and black cherry juice. The overall goal is to eliminate substances believed to cause agglutination and digestive stress.
Lack of Scientific Evidence and Safety Considerations
The Blood Type Diet, including the specific recommendations for Type O+, is not supported by mainstream nutritional science. Multiple systematic reviews have concluded that there is no scientific evidence to validate the purported health benefits of eating according to one’s ABO blood type. These claims are not recognized by major medical or dietary organizations.
Any reported health improvements experienced by followers are likely due to the general shift toward healthier eating habits, such as eliminating processed foods and increasing intake of lean protein and fresh vegetables. Because the Type O diet is highly restrictive, it may lead to nutrient deficiencies if not carefully managed. Consulting a registered dietitian or physician is strongly recommended before making significant changes, especially those that eliminate entire food groups.