FULL CLAIM: “Foods to eat according to your blood type [...] Understand why knowing your blood type is crucial for optimizing your nutrition and lifestyle”; “Did you know Brocolli [sic] is considered MEDICINE for everyone that has O Negative Blood type? [...] I been eating for my blood type and I feel AMAZING”
REVIEW
Posts shared on Instagram in June and July 2024 claimed that eating certain types of foods based on blood type can help to optimize health and nutrition (examples here, here, and here). The posts collectively received thousands of interactions.
Variations of this claim, which alleged that this “blood type diet” could help promote weight loss, previously circulated in Chinese on Weibo and Facebook. English versions of this claim date back as far as 2012. AFP fact-checked these claims in 2023 and determined them to be false.
As we will explain below, there is currently no scientific evidence supporting an association between blood type, diet, and health.
Understanding blood type is important for certain medical procedures
Blood types are primarily classified into two groups: ABO and Rh. The ABO blood group system divides types into four categories (A, B, AB, and O) based on the presence or absence of A or B antigens. Antigens are proteins which are markers that tell the immune system whether a cell is foreign or from the same body. A or B antigens are present on the surface of red blood cells and in plasma depending on one’s blood type. The Rh blood group system divides types into positive (+) or negative (-) based on the presence or absence of the Rh antigen on red blood cells.
Knowing one’s blood type is important for medical procedures such as blood transfusions, cancer treatments, and surgeries, and to replenish blood loss from traumatic injuries. Blood type compatibility is critical for avoiding adverse reactions to blood transfusions such as organ transplant rejection. In some cases, receiving the wrong blood type can lead to death.
Currently no evidence that diet based on blood type improves health
While our blood type is critical for ensuring safe blood transfusions, whether or not it affects our health by influencing our reaction to a specific diet is much less clear.
The “blood type diet”, originally coined by naturopathic doctor Peter D’Adamo in the mid-1990s, purports that eating certain foods based on one’s blood type can positively impact health by boosting energy, promoting weight loss, lowering inflammation, and preventing disease. The diet is divided into four subgroups based on the ABO blood group system. As we explain in greater detail below, each subgroup prioritizes eating certain foods. However, on the whole, all the subgroups recommend consuming a mix of fruits, vegetables, lean proteins, and grains.
We searched PubMed, a digital repository of articles maintained by the U.S. National Library of Medicine, for articles containing “blood type diet” in their title or abstract. The search yielded seven results: four published in English and three published in Norwegian.
One study of nearly 1,500 participants from Wang et al. evaluated whether adhering to blood type diets impacted the health of individuals of corresponding blood types, for instance, participants with type O blood adhering to the “type-O diet”. They found that while all of the blood type diets showed some benefits in terms of cardiometabolic risk factors such as BMI, waist circumference, blood pressure, and triglycerides, these associations didn’t correspond to participants’ blood type and thus “do not support the ‘Blood-Type’ diet hypothesis”[1].
A systematic review published in The American Journal of Clinical Nutrition in 2013[2] narrowed down 16 studies from a screened pool of over 1,400 articles and determined that just one of the 16 studies met the researchers’ inclusion criteria.
This study looked at cholesterol levels among different blood types in response to a “low-fat diet” rather than specific adherence to any of the “blood type diets”[3], but the authors of the review ultimately determined that no evidence existed to validate an association between blood type and diet.
Another small study among individuals with type A and type O blood similarly found no association between blood type and cardiometabolic outcomes among participants who adhered to a plant-based diet[4].
What is the origin of the “blood type diet”?
In 1996, D’Adamo published Eat Right 4 Your Type, a book with recommended dietary choices, exercise regimens, and activities like meditation based on blood type that allegedly improve health. On his website, the book is described as a “[r]evolutionary nutrition guide that introduced The Blood Type Diet to the world”.
D’Adamo claimed that the way we digest food is linked to when our blood type developed and the foods most commonly eaten during that time. In 2022, rheumatologist Robert H. Schmerling wrote an article for Harvard Health which shared a description of each blood type diet in greater detail:
“Type O was said to be the original ‘ancestral’ blood type of the earliest humans who were hunter-gatherers, with diets that were high in animal protein. Group A was said to evolve when humans began to farm and had more vegetarian diets. Group B blood types were said to arise among nomadic tribes who consumed a lot of dairy products. And since Group AB blood was supposed to have evolved from the intermingling of people with types A and B blood, type AB recommendations were intermediate between those for people with types A and B blood.”
However, the article didn’t endorse the blood type diet, citing a current lack of evidence for its efficacy. Schmerling elaborated:
“Each of these theories has been challenged. For example, there is evidence that type A was actually the first blood group to evolve in humans, not type O. In addition, there is no proven connection between blood type and digestion. So, in addition to a lack of evidence that the diet works, serious questions remain about why it should work in the first place.”
Conclusion
The foods recommended by the “blood type diet” largely consist of fruits, vegetables, lean proteins, and grains, which generally benefit cardiometabolic health. However, there is no evidence to suggest that there are health benefits to eating more or less of any of these types of food groups based on one’s blood type.
REFERENCES
- 1 – Wang et al. (2014) ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors. PLOS ONE.
- 2 – Cusack et al. (2013) Blood type diets lack supporting evidence: a systematic review. The American Journal of Clinical Nutrition.
- 3 – Birley et al. (2008) MN blood group affects response of serum LDL cholesterol level to a low fat diet. Clinical Genetics.
- 4 – Barnard et al. (2021) Blood Type Is Not Associated with Changes in Cardiometabolic Outcomes in Response to a Plant-Based Dietary Intervention. Journal of the Academy of Nutrition and Dietetics.
