Peter D'Adamo, a naturopathic doctor and author of "Eat Right for Your Type," has gained international acclaim for outlining individualized diet plans based on blood type. D'Adamo claims that your blood type partly determines your likelihood of developing chronic illnesses and that adhering to the Blood Type Diet will prevent these ailments and help you reach your optimal weight.
The theory behind the Blood Type Diet is based on a chemical reaction between lectins -- sugar-binding proteins found in foods -- and your blood type. Proponents of the Blood Type Diet suspect that when you eat food containing lectins that are incompatible with your blood type, the lectins target your organs causing disease and adverse effects. Symptoms may include weight gain, fatigue and poor digestion. The theory also claims that your stomach acid and digestive enzyme levels are associated with your blood type, and you must eat certain foods that will be readily digested and absorbed.
Blood Type A
According to the Blood Type Diet, those with blood type A are best suited for a vegetarian diet that consists of fresh and organic fruits, vegetables, grains, legumes and soy proteins. D'Adamo states that people with type A blood should model their diet after their ancestors who had more settled and less warlike farming lifestyles. He claims that those with type A blood are more prone to heart disease, cancer and diabetes, and adopting a diet suited for this blood type will boost their immune system and help prevent disease.
Blood Type B
Type B individuals have strong immune systems and very resilient digestive systems, according to proponents of the Blood Type Diet. As a result, they are more resistant to many chronic illnesses. D'Adamo states that people with type B blood are descended from travelers who were exposed to many varieties of food. Thus, those with type B blood are able to thrive on a balanced diet without many limitations. The type B diet has the fewest restrictions and focuses mainly on balance. Type B individuals should avoid processed foods, corn and seeds.
Blood Type AB
Those with type AB blood are the most biologically complex with regard to evolution, so this is considered the "modern" blood type. The blood type AB diet emphasizes a combination of type A and type B diets, in moderation. D'Adamo states that type AB individuals should focus on tofu, seafood and dairy along with vegetables and limit red meat and cured meats. They should also avoid caffeine and alcohol, especially when they experience stress.
Blood Type O
D'Adamo believes that those with type O blood are descendants of typical hunter-gatherers, and their digestive tracts retain the memory of these ancestors from the oldest blood line. They should adhere to a high-protein diet with plenty of lean meats, poultry and fish. Type Os should limit dairy and carbohydrates such as grains and legumes.
This diet may be convenient for some as it doesn't require counting calories, but it may present challenges in that you have to restrict certain types of food based on your blood type. Dr. Melina Jampolis, a physician nutrition specialist, does not fully embrace the principles of the Blood Type Diet. She cautions that the diet may cause harm by either prompting you to eat large amounts of certain food groups while eliminating other groups entirely. She considers this diet to be a form of alternative medicine that requires additional research.
Christina Marie is a health writer based in Buffalo, N.Y. She holds a Master of Science in nutrition science and enjoys helping others reach their own optimum wellness. She also works as a nutritionist and lactation consultant.