Blood
Is the Blood Type Diet Backed by Scientific Evidence?
Nov
The blood type diet is the basis of a book published in 1996 by naturopathic physician Peter D’Adamo. The book outlined suggestions for increasing health benefits by eating foods corresponding to your blood type. While the book was popular, the blood type diet is not backed by evidence, and its claims are not substantiated.
Blood type diet theory proposes that those with group A blood should eat a mostly vegetarian diet, those with group O should focus on high animal protein, and those with group B should eat dairy products. It recommends a diet that has elements of both the A and B diet for people with AB blood.
This article will discuss how the blood type diet is proposed to work, foods suggested by the diet for each blood group, if there are benefits for eating for your blood type, considerations, and dietary restrictions with a blood type diet.
Jordi Salas / Getty Images
How Is the Blood Type Diet Claimed to Work?
The major ABO blood group is based on determined by which antigens (substances that can trigger an immune response) are present on the surface of red blood cells. A antigen, B antigen, both, or neither may be present, resulting in the blood types A, B, AB, and O.
The blood type diet proposes that because of evolutionary history, blood type can affect how certain foods are digested. By extension, eating accordingly could provide health benefits.
The theory is that type O was the original “ancestral” blood type, meaning the blood type of the earliest humans. Based on the diets of early humans as hunter-gatherers, the diet claims people with this blood type are best suited to eating animal protein.
Theoretically, group A blood evolved when humans began to farm and consume a more vegetarian diet, and group B blood was developed among nomadic tribes who had a high consumption of dairy. The AB type formed through reproduction between people with type A and type B blood.
However, there is evidence that the first humans had blood types in addition to type O. Their close relatives (including Neanderthals) have types A, B, and O. In primates, types A and O are seen in chimpanzees, A and B in gorillas, and A, B, and AB in orangutans and gibbons.
Blood Types and Health
Older research from the 1950s and 1960s compared blood types for the risk of ischemic heart disease (coronary artery disease). People with type O blood had a modest reduction in risk compared to those with other blood types.
A 2016 meta-analysis of case-control and cohort studies found evidence that supported these earlier studies, with findings suggesting a 15% reduced risk of coronary artery disease (CAD) for blood group O.
Other studies have suggested that people with type A blood have an increased risk of higher total cholesterol and low-density lipoprotein (LDL) cholesterol (considered bad cholesterol) concentrations. Studies have found inconsistent relationships between blood types and the risk of type 2 diabetes.
These findings have prompted questions about whether a person could benefit from dietary choices tailored to their blood type. There is a lack of research on this subject, and the limited amount of observational data does not support the health benefits of eating based on blood type.
Blood Type O Foods
According to the blood type diet theory, those with type O blood should eat:
- Meat (including red meat)
- Fish
- Vegetables (such as broccoli and spinach)
- Fruit
They should limit:
- Grains
- Beans
- Legumes
For weight loss, they should avoid:
- Wheat
- Corn
- Dairy
Blood Type A Foods
The blood type diet theorizes that people with type A blood should eat:
- Fruit
- Vegetables
- Tofu
- Seafood
- Turkey
- Whole grains
They should avoid red meat.
For weight loss, they should avoid:
- Dairy
- Wheat
- Corn
- Kidney beans
Blood Type B Foods
Following the blood type diet theory, those with type B blood should eat a diversity of foods, including:
For weight loss, they should avoid:
- Chicken
- Corn
- Peanuts
- Wheat
Blood Type AB Foods
Blood type diet theorizes that people with type AB blood should eat:
- Dairy
- Tofu
- Lamb
- Fish
- Grains
- Vegetables
For weight loss, they should avoid:
- Chicken
- Corn
- Buckwheat
- Kidney beans
Proposed Benefits of Eating Based on Your Blood Type
Studies examining the blood type diet found that the dietary suggestions for type A (increased intake of fruits, vegetables, and grains) did benefit those with type A blood, but they also benefited those with types O, B, and AB.
A 2014 study found that the different proposed eating plans had certain health effects, but these were not impacted by blood type. For example, a diet rich in vegetables, fruits, and whole grains that limits red meat, such as the type A recommendations, is associated with cardiovascular health benefits regardless of a person’s blood type.
Similarly, the diet proposed for group AB, which advises limiting butter and eating eggs and fish as the main animal proteins, is associated with a more favorable cardiometabolic profile (tests for heart health and blood sugar management) than the type B plan, which has fewer restrictions on many animal products. These results applied to people of all blood types.
What Does the Research Say?
There is a lack of high-quality studies published in peer-reviewed medical literature on the blood type diet.
The main findings of existing studies examining the influence of blood type on diet and health benefits include:
- Health outcomes from the foods recommended for each blood type are related to the foods eaten, not the blood type, and are not unique to any blood type.
- Regardless of blood type, those whose eating patterns are similar to those outlined for the type A blood group (more fruit, vegetables, and grain, less meat) tend to have better cardio-metabolic (cardiovascular and metabolic) outcomes, such as lower body mass index (BMI), waist circumference, serum cholesterol and triglyceride levels (fats in the blood), and insulin resistance (when cells in the body don’t respond well to the hormone insulin and have difficulty taking up glucose from the blood, requiring more insulin).
- The type O diet recommendations (emphasizing meat, fruits, and vegetables and limiting grains) have been associated with lower triglyceride levels, regardless of the person’s blood type.
- Evidence does not support using blood type as a basis for determining what foods to eat or avoid.
Considerations
Health claims made by the blood type diet should be viewed as theoretical and not supported by scientific evidence.
Following an eating plan based on your current health concerns and family history makes more sense and has more research backing it. Eating plans such as the Mediterranean diet, the DASH (Dietary Approaches for Stopping Hypertension) diet, and certain anti-inflammatory diets have more substantial supporting evidence regarding health benefits.
Dietary Restrictions
Following the recommendations for your blood type could be difficult with your dietary restrictions. For example, the type O recommendations that emphasize meat would go against the guidelines of a vegetarian or vegan eating pattern.
Talking to a registered dietitian can help you find evidence-based eating plans that fit your goals and lifestyle.
Summary
The blood type diet is based on a book that proposes eating foods tailored to your blood type could have health benefits, such as a mostly vegetarian diet for type A and an emphasis on animal protein for type O.
There is no quality evidence that blood type impacts dietary choices or that there is a benefit to choosing an eating plan based on blood group.
Any health benefits from eating according to the suggestions for each blood type apply to anyone who follows them regardless of blood type.
Instead of following a diet based on your blood type, it is advisable to choose evidence-based eating plans that address your health concerns, such as the DASH diet and/or talking to a registered dietitian.
