D'Adamo’s theory is that your blood type determines which foods you are best suited to.
Blood group O (humanity's oldest blood line – approximately 30,000 years old) is described as the hunter. He recommends that those of this blood group eat a higher protein diet. Vigorous exercise is recommended.
Blood group A is called the agrarian or cultivator. This type dates from the dawn of agriculture 20,000 years ago. The recommended diet for these individuals is vegetarian. Gentle exercise is recommended
Blood group B is called the nomad. This group is thought to have arrived 10,000 years ago. They are associated with a strong immune system and a flexible digestive system. They are the only people able to thrive on dairy products. It is recommended they exercise moderately
Blood group AB is described as the enigma. This is the most recently evolved type arriving less than 1,000 years ago. They are said to have a sensitive digestive tract and are recommended to avoid chicken, beef, and pork. Seafood, tofu, dairy, and most other produce is fine though. The fitness regimen for ABs is calming exercises.
Foods fall into three categories - highly beneficial, neutral and avoid
Although this diet ‘sounds scientific’ it is not. There is no evidence that it works. On the contrary there are some contradictions, for instance people from China and India who are commonly Type Bs, are supposed to thrive on dairy but in fact are frequently lactose intolerant.