What is the Blood Type Diet?
The blood type diet was designed by naturopath Peter D'Adamo. The basis for the diet is his claim that the foods we eat react with our blood type, and therefore ‘eating for your type’ will help make you healthier, lose weight, prevent disease, and give you more energy.
Furthermore, he claims that by following a diet specific to your blood type, your body will digest food more efficiently and effectively.
What do the different types look like?
There are four different diets for blood types O, A, B, and AB. Each has specific foods to focus on and to avoid, and recipes are suggested to help follow each diet.
The Type A Diet
For type A individuals, a vegetarian diet is recommended due to a supposedly sensitive immune system in this group. The diet is therefore based on fruits, vegetables, legumes, beans, and wholegrains, all of which are ideally fresh and organic. Recipes for this diet include buckwheat pancakes and spinach omelette.
The Type O Diet
For these who are a type O, D’Adamo promotes a diet that is in high in protein, with a particular focus on lean meat, fish, poultry, and vegetables. Foods to avoid are grains, beans, and dairy. The premise behind the type O diet is that these individuals are prone to stomach issues, and along with the diet, supplements are also suggested to help with this. Recommended recipes include chicken salad wraps and butternut squash soup.
The Type B Diet
D’Adamo recommends that type B individuals should focus on green vegetables, some meats, low fat dairy, and eggs, whilst avoiding corn, buckwheat, lentils, sesame seeds, peanuts, chicken, wheat, and tomatoes. For this diet suggested recipes include lamb curry and granola.
The Type AB Diet
According to D’Adamo, those with a type AB blood type tend to have low levels of stomach acid and therefore should avoid caffeine, alcohol, and smoked/cured meats. Recommended foods include tofu, seafood, green vegetables, and dairy. Suggested recipes include tofu stir fry and fish stew.
Not only do individuals following any one of these diets have to focus on certain foods and restrict others, there are also certain types of exercise for each blood type. Type As are recommended to partake in yoga or tai chi, with type Os suggested to do more vigorous exercise such as running or cycling for up to an hour a day.
Why is it popular?
In a time where lots of people struggle with weight loss, and dietary advice is often conflicting and therefore confusing, people often seek advice that tells them what is healthy and unhealthy in relatively black and white terms.
The result of this is that diets like the blood type diet can gain popularity. However, it is very important to note that this diet pays no attention to any existing health conditions, for example high cholesterol, diabetes, or Crohn’s disease, and therefore the advice may conflict with national guidelines and individual dietary plans. Another issue is cost, with a focus on organic foods and supplements, this diet is expensive to follow.
The benefits and downsides?
Encouraging increased consumption of healthy foods such as vegetables, wholegrains, beans, and lentils, and reducing processed foods and refined carbohydrates is likely to result in weight loss for the individual. Weight loss is also likely to occur purely due to the restrictive nature of the diets.
However, in the long term, people typically find restrictive diets difficult to maintain, and this diet does not allow for any personal or cultural preferences.
What does the research say?
There is not a huge literature base on this diet, likely due to a lack of credibility in the scientific community.
This was demonstrated by a systematic review published in 2013 which attempted to analyse all the published studies that presented data related to blood type diets. The authors identified 16 studies from a total of 1,415 screened references, of which only one study was considered eligible according to the selection criteria.
The identified study investigated the variation between LDL-cholesterol and blood type when adhering to a low-fat diet, and therefore did not directly investigate D’Adamo’s hypothesis. As a result, the review concluded that ‘no evidence currently exists to validate the purported health benefits of blood type diets’.
However, a 2014 study assessing the blood type diets and their impact on cardiometabolic risk factors did observe the following; the type A and type AB diets were associated with lower BMI, waist circumference, blood pressure, serum cholesterol, triglycerides, and insulin, adherence to the type O diet was also associated with lower triglycerides, and no association with the biomarkers was observed for the type B diet.
The key finding from this study was that these effects were observed irrespective of the blood type of the individual following the diet, therefore suggesting there is no additional benefit of following the diet that matches your corresponding blood type. The full study can be found here.
Considering the evidence and what we currently know in terms of protective diets, such as that the Mediterranean diet is shown to be beneficial irrespective of blood type, it is unlikely that the blood type diet has any basis in science, and encourages individuals to follow restricted diets unnecessarily.