The Cold Truth About The Blood Type Diet-No Evidence

BY: KEN KLEINBERG

As I am writing this it is 6/11/25.

I have run into a number of people now that have said that they are on or have done the Blood Type Diet.
Some say that they have lost weight and others say that they feel better.  I will get into both of those in a bit.

And I have to say for myself, I am not a big fan.  I am not a big fan of ANY diets for that matter.  Diets are what is keeping people from making real life and lifelong changes in their life that produces lasting results.

95% of the people out there can't keep the weight off once they lost it.  I, on the other hand, have keep my weight off for 7+ years now all without a diet and having that be sustainable.  Why?  Because I did not go on a diet!  I approached my journey in a way that was sustainable for the long-haul, not just a short time.

Therefore, every new change and habit that I adapted into my journey simply had enough time to sink in and become part of who I was internally and had enough time to become automatic.  So by the time that I reached my weight goal, it was easy for me to stay because I had not only changed externally but INTERNALLY AND MENTALLY!!  If you have been in my world long enough, you know this!  Diets rob you of the real and long lasting transformation.

And in my eyes, the same goes for the Blood Type Diet!!!  Here is the thing...there is literally NO scientific evidence or basis.  Ok then, why do so many get a great result from it?  Well, to be honest, it's because for the most part, whatever blood type they are really has nothing to do with the equation. It's literally because they began turning away from premade, boxed, packaged, processed foods, and eating more real and whole foods.

Maybe it wasn't so much of the processed foods as it was that they simply began eating more foods with one ingredient.

Honestly, there is no scientific data to legitimize this diet.

• There is no scientific data that shows that matching your eating routine up with your blood type will help with your health in away way.
• There just is no scientific basis for it. There have been studies done with the methods of the state and the studies show that no evidence currently exists.

Here's another thing to think about: what if a family of mom and dad and 2 kids...lets say...and the dad has type A, the mom is type O, one of the kids is A, and the other is B.  This type of diet is would mean chaos and it would not be sustainable.  I say it again, it should NEVER be about a diet!

What is also interesting, is that the book that talks about the blood type diet, came out in 1996.  And it seems like today its been talked about like it's the newest thing.  If there really was any validity behind this particular "diet" don't you think there be more studies and research that would be out there to show the validity of it?

Ah, but the truth is that there is not!!!!

Honestly, it's just another fad diet that somebody came out with a long time ago that all the sudden has become the new fix!  

So just what is the Blood Type Diet?

Here's a brief overview of the suggested dietary recommendations for each blood type: 

• Blood Type O:
  • High Protein: Blood type O individuals are often advised to focus on a high-protein diet, including lean meats, fish, and poultry.
  • Limited Grains: Grains, particularly wheat, are generally discouraged for type O individuals.
  • Moderate Fruits and Vegetables: Emphasis is placed on consuming fruits and vegetables, except for certain types like corn.
• Blood Type A:
  • Plant-Based: Blood type A individuals are often recommended a primarily plant-based diet, including vegetables, fruits, legumes, and whole grains.
  • Limited Meat: Red meat is typically discouraged, and poultry and fish are suggested in moderation.
  • Low Dairy: Limited intake of dairy products is advised.
• Blood Type B:
  • Balanced Diet: Blood type B individuals are encouraged to have a balanced diet with a variety of foods, including meat, dairy, grains, fruits, and vegetables.
  • Moderate Dairy: Dairy products are generally well-tolerated by type B individuals.
  • Avoid Chicken: Chicken is often discouraged for type B individuals.
• Blood Type AB:
  • Mixed Diet: Blood type AB individuals are recommended a mix of the diets suggested for types A and B, incorporating a variety of foods.
  • Limited Red Meat: Red meat is advised in moderation, while poultry and fish are generally better options.
  • Moderate Dairy: Similar to type B, dairy products can be consumed moderately.Here's a brief overview of the suggested dietary recommendations for each blood type: 

    • Blood Type O:
      • High Protein: Blood type O individuals are often advised to focus on a high-protein diet, including lean meats, fish, and poultry.
      • Limited Grains: Grains, particularly wheat, are generally discouraged for type O individuals.
      • Moderate Fruits and Vegetables: Emphasis is placed on consuming fruits and vegetables, except for certain types like corn.
    • Blood Type A:
      • Plant-Based: Blood type A individuals are often recommended a primarily plant-based diet, including vegetables, fruits, legumes, and whole grains.
      • Limited Meat: Red meat is typically discouraged, and poultry and fish are suggested in moderation.
      • Low Dairy: Limited intake of dairy products is advised.
    • Blood Type B:
      • Balanced Diet: Blood type B individuals are encouraged to have a balanced diet with a variety of foods, including meat, dairy, grains, fruits, and vegetables.
      • Moderate Dairy: Dairy products are generally well-tolerated by type B individuals.
      • Avoid Chicken: Chicken is often discouraged for type B individuals.
    • Blood Type AB:
      • Mixed Diet: Blood type AB individuals are recommended a mix of the diets suggested for types A and B, incorporating a variety of foods.
      • Limited Red Meat: Red meat is advised in moderation, while poultry and fish are generally better options.
      • Moderate Dairy: Similar to type B, dairy products can be consumed moderately.

Like I said earlier, it just sounds like another fad diet to me.  There is no one-size-fits-all!  Even with this!

And again you need to realize, when they follow this plan they are going on a diet.  Completely wrong mindset.  They might be able to sustain it for a while, but I can almost guarantee you, somewhere down the line they will gain their weight back.  

In a large 2014 study published in the journal PLOS ONE, researchers looked at over 1,400 people. While some experienced health improvements from eating “cleaner” based on their blood type recommendation, those results were independent of their blood type.

Translation? People felt better not because they ate for their blood type, but because they cut out processed junk, ate real food, and reduced inflammation, no matter what blood type they were.

“Oftentimes, trendy diets come up with ‘one-size-fits-all’ programs, providing the same recommendations for everyone,” said Jennifer Oikarinen, a registered dietitian at Banner - University Medical Center Phoenix. “In contrast, the blood type diet offered a different and distinct set of guidelines that appealed to many people—hence its popularity.” While it’s tailored very specifically to those O, A, B and AB and seems like a no-brainer, is the blood type diet legit—and has it been proven to actually work? “Simply put: No,” Oikarinen said. “The blood type diet is based solely on observations made by the author. Results and claims regarding the diet have not been measured or proven to be successful in a clinical trial or research study.” Dr. D’Adamo hadn’t produced his own research, so independent researchers decided to take it upon themselves to evaluate the diet, and 2013 and 2014 studies found no scientific evidence to suggest any benefit or claims associated with a person’s blood type." ~ https://www.bannerhealth.com/healthcareblog/teach-me/the-blood-type-diet-does-it-really-work -- The Blood Type Diet: Does It Really Work?- By Regan Olsson

 And here is a quote from the 2013 study (Listed in the above quote):

“A 2013 systematic review in the American Journal of Clinical Nutrition concluded: ‘No evidence currently exists to validate the purported health benefits of blood type diets.’ Despite screening over 1,400 studies, the researchers found zero clinical trials that demonstrate eating for your blood type actually improves health outcomes. Any benefits seen are not linked to blood type but rather to overall improvements in dietary quality.” 

Here is another thing to think about; there are also no peer reviewed studies that have been done on Dr. Peter D’Adamo for his book Eat Right 4 Your Type.  In light of that, there are three things to keep in mind.

1. No peer-reviewed human trials have validated his claims.
2. D’Adamo has never published primary data to back his theory in reputable medical journals.
3. Instead, the platform is based entirely on anecdotal cases, testimonials, and untested hypotheses.

While some integrative doctors briefly entertained the theory decades ago, most functional and ancestral-based practitioners today (Dr. Ken Berry, Dr. Cate Shanahan, Dr. Shawn Baker, etc.) have rejected it because of:

• Lack of reproducible results
• Too much complexity without benefit
• No long-term adherence success stories

Dr. Berry has clearly said:

“Blood type diets are pseudoscience at best. There is zero clinical evidence that it’s a valid approach. Stick with what humans were designed to eat.”

There is one more well known author and speaker that will mention before concluding.  Nina Teicholz.

I love her work and she has a powerful book call "The Big Fat Surprise".  

Nina is relentless about calling out nutrition advice that is not grounded in rigorous, randomized clinical trials (RCTs). The Blood Type Diet has zero RCT support, zero clinical trial replication, and no peer-reviewed validation.“The sad truth is that much of our nutritional guidelines are based on weak science—hypotheses that were never proven.” ~ Nina Teicholz, The Big Fat Surprise

If it’s not scientifically sound? She won’t back it. Period.  Nina is a great person and source to follow.

So, I am going to conclude with this.  The Blood Type Diet suggests nutritional needs vary wildly depending on your blood type. But I simply see a completely different reality and truth.  I want to point out that human physiology has universal truths:

• We all need complete proteins

• We all benefit from saturated fats

• We all suffer when consuming ultra-processed, refined carbs and seed oils

These principles do not change based on your ABO blood type. I would argue that to tailor your diet based on blood type is divorced from real biology and human evidence.

I would firmly say that the Blood Type Diet is an unscientific, over-hyped diet fad, and one that distracts from real, ancestral, animal-based nutrition that has been healing humans for millennia.

Here is another quote that found when talking about the Blood Type Diet and the popular book "Eat Right For Your Type" :

"So, what should the overall assessment of this work be? The nicest thing you can say about the book is: “boy, does he have a good imagination.”

Is it any worse than people who believe their fate is determined by the stars? Well, yes, because astrologists aren’t telling a third of the population to go out and eat organ meats.

The diet is not as bad as some. Positive results reported by some individuals may well be due to a general improvement in diet and lifestyle (less fat and sugar, more fruits and vegetables, less smoking, more exercise). Look, anything that gets people to eat fewer doughnuts, I don’t care if you say Martians said so.  

This may get lost a bit in translation, but this professor of laboratory medicine at the Norwegian University of Science’s analysis concluded that the author’s “learning must be considered junk and without scientific foundation.”

What did the new review find? They sifted through over a thousand papers that might shed some light on the issue, and none of the studies showed an association between blood type diets and health-related outcomes. They conclude that there is currently no evidence that an adherence to blood type diets will provide health benefits, despite the substantial presence and perseverance of blood type diets within the health industry." ~ https://www.afpafitness.com/blog/https-www-afpafitness-com-research-articles-blood-type-diet-review/. - By: Dr. Michael Greger

And here is another little quote from an article that I found:

"Most participants saw improvements, it’s just that no one group saw greater results for cholesterol, BMI, fasting blood sugar, HbA1c, or weight loss than another due to blood type. If the blood type diet had merit, the low fat vegan diet should have been well suited to type A blood types and not as well suited for those with type O blood, who under the rules of Dr. D’Adamo’s protocols would be healthier on a diet with more animal protein.

Based on the cardiometabolic markers studied, this turned out not to be the case, which may have put the final nail in the coffin for the blood type diet, at least within the scientific community.

So is that the end? Are blood type and diet definitively not linked? Well in the sense that you should follow a particular diet based on your blood type, yes. In that respect, the blood type diet has been debunked."
~ https://www.mygenefood.com/blog/blood-type-diet-debunked/?  - By: Dr. Aaron Gardner, BSc, MRes, PhD

That last one that I just quoted at the end of his article has a list of sources to look through.  So again as I commonly say, "Do your research!"

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