According to the blood type diet, people with B positive blood should eat a varied, mixed diet rich in dairy, certain meats, seafood, fruits, and green vegetables. This dietary approach was popularized by Dr. Peter D’Adamo in his 1996 book “Eat Right 4 Your Type,” which assigns specific food recommendations to each blood group. However, the largest study to test this theory found no evidence that eating for your blood type provides any unique benefit, so it’s worth understanding both the recommendations and their limitations.
The Theory Behind the Type B Diet
D’Adamo labeled Type B the “Nomad” blood type, theorizing it originated around 15,000 B.C. among nomadic herding populations. Because these ancestors raised livestock and moved across varied landscapes, the theory goes, people with Type B blood evolved to digest a wider range of foods than other blood types, especially dairy. Of the four blood types in this system, Type B is the only one considered well-suited to regular dairy consumption.
The core idea is that certain proteins in food called lectins interact differently with each blood type. When you eat foods containing lectins that are incompatible with your blood type, D’Adamo argues, they can cause inflammation and other problems. Foods are therefore sorted into three categories: highly beneficial, neutral, and those to avoid.
Foods the Type B Diet Encourages
The Type B diet is one of the more flexible versions, emphasizing a balanced mix of animal protein, produce, and dairy. The recommended foods include:
- Meats: Lamb, goat, rabbit, and venison are considered highly beneficial. These are the centerpiece proteins of the diet.
- Seafood: Fish like salmon, cod, and sardines are encouraged.
- Dairy: Low-fat dairy products such as yogurt, kefir, and farmer’s cheese are a distinguishing feature of this plan. Type B is treated as uniquely dairy-friendly.
- Eggs: Considered a staple protein source.
- Green vegetables: Leafy greens like kale, broccoli, and collard greens are emphasized.
- Fruits: Most fruits are considered acceptable, with grapes, bananas, and pineapple frequently listed as beneficial.
- Grains: Spelt bread and oat-based products are favored over wheat. Rice is generally considered neutral.
A typical dinner on this plan might look like grilled lamb chops with a mint-yogurt sauce and a side of steamed greens. Breakfast could be eggs with fruit and yogurt. The overall pattern resembles a Mediterranean-style approach with an emphasis on whole foods and dairy.
Foods the Type B Diet Says to Avoid
The avoid list for Type B is specific and, in some cases, surprising. D’Adamo recommends steering clear of:
- Chicken: This is the most unexpected restriction. While other meats are encouraged, chicken is considered problematic for Type B because of a specific lectin in its muscle tissue that D’Adamo claims can cause clumping in Type B blood.
- Corn: All forms, including corn muffins and taco shells, are on the avoid list. Spelt-based alternatives are suggested as replacements.
- Wheat: Standard wheat products are discouraged, though spelt and other ancient grains are treated as acceptable.
- Lentils and peanuts: Both are said to interfere with Type B metabolism.
- Buckwheat and sesame seeds: These are flagged as containing lectins that are particularly reactive for Type B individuals.
- Tomatoes: Another common food that lands on the restricted list for this blood type.
The restrictions around corn, wheat, and lentils mean that many processed and packaged foods are automatically excluded, which tends to push followers toward a whole-foods eating pattern regardless of their blood type.
What the Science Actually Shows
The most rigorous test of the blood type diet came from a study published in PLOS ONE by researchers at the University of Toronto. They analyzed the diets of over 1,400 people and measured markers of heart and metabolic health. Their conclusion was clear: following certain blood type diets did improve some health markers, but the improvements had nothing to do with the person’s actual blood type. Someone with Type O blood benefited just as much from the Type B diet as someone who was B positive.
In other words, the diets themselves can be healthy, but the match between diet and blood type doesn’t matter. The researchers noted this likely explains the anecdotal success stories. People who follow the Type B diet tend to eat more vegetables, lean meats, and whole foods while cutting out processed grains and junk food. That pattern improves health for virtually everyone.
No major medical organization endorses eating based on blood type. The improvements people experience likely come from the overall quality of the food rather than any interaction between lectins and blood cells.
Why People Still Feel Better on This Diet
If there’s no scientific basis for matching food to blood type, why do so many people report feeling healthier? The answer is straightforward. The Type B diet eliminates many processed foods, reduces wheat and corn intake, emphasizes vegetables and lean protein, and encourages home cooking. These are all changes that improve energy, digestion, and overall health for most people, regardless of whether their blood type is B, A, O, or AB.
There’s also a powerful psychological component. Having a clear framework for what to eat and what to skip removes decision fatigue. People who follow any structured eating plan tend to make more deliberate food choices, eat fewer snacks, and pay closer attention to ingredients. That mindfulness alone can produce noticeable results.
If the Type B food list appeals to you and feels sustainable, there’s nothing wrong with following it as a general healthy eating template. The foods it encourages, like green vegetables, fish, yogurt, lamb, and eggs, are nutrient-dense and well-supported by mainstream nutrition science. Just know that the benefit comes from the food quality, not from a special connection to your blood type.