What science says about Blood Type Diet For Cancer

Different medical doctors and health experts have conflicting opinions on the blood type diet for cancer.

Supporters of the blood type diet claim that the genetic linkage between ABO blood group antigens and cancer may predict an individual’s susceptibility to cancer. They also claim that if each blood type eats specific foods with anti-cancer properties, they can boost their immune system function and fight cancer more effectively. Plus, if each blood type avoids harmful lectins, they can regulate immune system function and focus the body’s energy on finding and killing cancer cells.

Meanwhile, the diet’s opponents claim that there is no scientific evidence that supports the blood type diet. While they agree that the blood type may determine a person’s cancer risk, they find no evidence to suggest that eating specific foods according to blood type prevents or treats cancer. They even reject the main hypothesis behind the diet claiming that different foods can affect different blood types differently as they believe that a certain food affects all blood types similarly.

Nevertheless, opponents found the blood type diet to be beneficial for cancer patients only because it promotes healthy eating habits such as eating more fruits and vegetables and avoiding processed and sugary foods. By avoiding these foods, people do not consume toxins and other chemicals that alter their DNA resulting in mutations that may cause cancer. 

Opinion in favor of  following the blood type diet for cancer:

Peter D’Adamo, the creator of the blood type diet, claims that there is a genetic link between blood type and cancer. Scientific research validates this claim and indicates that some blood types are more at risk for certain types of cancer than other blood types depending on what antigens they have on their red blood cells.

In February 2020, a systematic review of cancer incidence in different blood types, “Association of ABO Polymorphisms and Pancreatic Cancer/ Cardiocerebrovascular Disease: A Meta-Analysis,” found that “ABO polymorphisms might serve as a risk factor of pancreatic cancers and cardiocerebrovascular diseases.” Thus, studies prove that blood type may be a factor that increases a person’s susceptibility to certain cancers.

However, there are no studies discussing whether a person’s susceptibility to cancer changes based on dietary changes according to blood type. Also, no research examines how changing one’s diet according to blood type affects a person’s risk of developing cancer.

Supporters of the diet also claim that eating foods with beneficial lectins will boost the immune system and help it fight cancer while other foods with harmful lectins will hinder immune system function. They also argue that eating the right foods for each blood type prevents the formation of blood clots and increased platelet count, which slows the spread of cancer in the body. 
Scientific research has found that some lectins may have anti-cancer properties and kill cancer cells. In 2003, a study called “The Anticarcinogenic Potential of Soybean Lectin and Lunasin,” found that the lectin in soy products can destroy cancer cells. D’Adamo recommends that blood type A and AB individuals eat soybean lectins to treat or prevent cancer.

In 2007, another study about lectins titled “Lectins as Bioactive Plant Proteins: A Potential in Cancer Treatment” found that some lectins have anti-cancer properties and can be used to kill cancer cells. This study indicates that Peter D’Adamo’s hypothesis about beneficial lectins targeting and destroying cancer cells is valid.

However, current research does not examine the effect of lectins based on different blood types. Instead, it suggests that plant lectins have great “potential as anti-cancer agents,” but calls for further research on the topic. 

Opinion against following the blood type diet for cancer:

Many medical experts believe that, although there is a link between an individual’s blood type and cancer, there is insufficient scientific evidence to support the hypothesis that the blood type diet, or eating particular foods according to our blood type, has any effect on an individual’s cancer prognosis.

Opponents of the diet argue that the blood type diet does not affect a person’s overall health compared to other diets. This is because lectins in food react with all blood types in the same manner. A 1980 study, “Lectins in the United States diet: a survey of lectins in commonly consumed foods and a review of the literature,” conducted by Nachbar and Oppenheim shows that lectins have agglutination properties, and lectins in legumes can be harmful to the human body. However, it does not indicate that different blood types have different reactions to lectins. Therefore, experts believe that the main theory behind the blood type diet is false.

Experts also claim that the blood type diet is not supported by scientific evidence. In 2013, a study by Cusack et al. titled, “Blood type diets lack supporting evidence: a systematic review,” analyzed studies presenting data about blood type diets. 
They found that these studies were poorly designed because the experiments lacked a control group of people following a standard diet. This works against the diet because it was difficult for researchers to compare the responses of people following the blood type diet to those following the standard calorie restriction diet. Therefore, researchers could not tell if people’s diseases improved because they followed the blood type diet or because of other factors.

Furthermore, opponents argue that not all plant lectins have anti-cancer properties, as D’Adamo claims. Although older studies have shown that peanut lectins have anti-cancer properties, in 2006 a study titled, “Peanut lectin stimulates proliferation of colon cancer cells by interaction with glycosylated CD44v6 isoforms and consequential activation of c-Met and MAPK: functional implications for disease-associated glycosylation changes,” indicated that peanut lectins promote the growth and spread of cancer cells.

This study casts doubt on D’Adamo’s claim that types A and AB individuals should eat peanuts to treat or prevent cancer. Scientists need to do more research to determine whether peanut and other lectins help destroy cancer cells. 
The diet’s opponents attribute the blood type diet’s cancer-fighting success to healthy eating habits, such as eating organic fruits and vegetables and avoiding processed meats, high sugar foods, and refined carbohydrates. Eating organic fruits and vegetables helps fight cancer because they contain fiber, which helps the digestive system clear out toxins before they can damage healthy cells.

Meanwhile, if people avoid processed meats, high sugar foods, and refined carbohydrates, which contain added sugars, they prevent cancer in multiple ways. These foods contain chemicals that may alter people’s DNA, resulting in genetic mutations that affect cell growth and cause cancer. They also contain toxins like sodium nitrite that may cause cancer.  
Thus, opponents argue that specific foods do not affect particular blood types in different ways. Food quality, not food type, is the main factor that affects an individual’s susceptibility to cancer.