The blood type diet created by Dr. Peter D’Adamo claims that eating a specific diet tailored to your blood type can be beneficial. He also claims eating for your blood type can even help lower risk for some diseases and help with weight loss.
While this theory may sound convincing, most health experts do not agree with D’Adamo about the scientific evidence for eating for your blood type.
Here is a further look at why the blood type diet may not be valid and how to determine a diet’s credibility.
What is the blood type diet?
The four types of blood humans have are type O, type A, type B and type AB. Depending on what type of blood you have will determine what diet and exercise program would best suit you, according to Dr. D’Adamo.
Why would people with different blood types need different diets? According to Dr. D’Adamo, proteins called lectins can be formed in the blood stream from different foods absorbed in the digestive tract. These lectins become active in the blood and may cause some adverse reactions in the body like low energy, digestive issues, weight gain etc.
A rationale for the blood type diet is that by avoiding the foods that produce lectins in your blood, your health will improve. According to the official website for Dr. D’Adamo and The Blood Type Diet ®, people will see benefits of a leaner and cleaner body and may have more energy when following this diet.
What can you eat based on your blood type?
According to the blood type diet, here are general guidelines of what to eat based on your blood type. More specific information can be found in Dr. D’Adamo’s book “Eat Right For Your Type”.
Blood type O: Your food intake should be based on eating more animal proteins, vegetables and very limited grains. This type of diet can be considered like a low carbohydrate diet similar to an Atkins based diet.
Blood type A: Your food intake should be based on a vegetarian diet.
Blood type B: Your food intake can have a higher intake of dairy.
Blood type AB: Food intake is similar to blood type B but focuses also on eggs and fish as a protein source.
Type O and A should especially avoid wheat and corn, as these can be a leading source of weight gain in these blood types.
Type B and AB should avoid corn based products and rely more on Spelt and other neutral grains according to Dr. D’Adamo.
What is the science behind the blood diet?
Dr. D’Adamo’s website claims he has ongoing research that confirms the theory that blood type is a key indicator for which foods cause inflammation, weight gain and digestive problems in people.
The rationale for what people can eat based on their blood type stems from the way humans have supposedly adapted over time. For example, type O blood is thought to be based on the hunter gatherers from around 50,000 BC, but blood type B was supposedly developed around 10,000 BC when there were different foods available for human consumption.
The blood type diet is based on when these blood types were introduced from human ancestors and applied to humans’ current diet. While Dr. D‘Adamo claims he has research backing up his claims, health professionals are not as easily persuaded the rational for this diet is sound.
Is the blood diet valid?
According to a study from the University of Toronto, the blood type diet is not valid.
Researchers analyzed over 1,400 subjects and concluded that diet, certain markers of health and blood type were not related. Subjects were assigned to eat based on their blood type, and researchers measured indicators of health such as blood cholesterol, triglycerides and insulin levels.
Researchers found that subjects in this study did show some health improvements, but they were independent of the subjects’ blood type. So, this could mean simply following a healthier diet, no matter what your blood type, can positively improve health.
There are not scientific studies that back up the claims of the blood type diet that support the theory of the blood type diet. In fact, a 2013 review article found no evidence was found to support the claims of blood type diets.
How do you know if diet claims are valid?
The scientific method is a way to ask and answer questions related to science via continual observations and experiments. In order for a health claim to have validity, it should have significant research results backing up the claim. Often popular diet books and plans are released and sound promising, but they do not have significant research backing their claims.
How can you know which scientific or health information is valid? Peer reviewed research is considered a gold standard in terms of quality research. Peer reviewed research papers are reviewed by other scientists in the field and are checked for unbiased results and proper steps. Major research journals publish only peer reviewed research.
Quantity and quality of the research are also important. More than one study is needed to confirm a hypothesis and preferably different kinds of study should support the hypothesis. Look at the size of the study. If a diet is making a claim based off a single study that had a sample size of less than 10 people that is not a strong indicator the study can be extrapolated to the general population. Research studies should be reproducible and come out with similar results.
Personal testimonies are not a real indicator of validity! Anyone can give a testimony if a diet or supplement worked, but it has no merit. Even if the person is a celebrity, personal testimonies do not give merit to a diet or supplement.
What about the people who lost weight or improved their health on the blood type diet?
People can lose weight on almost any diet. However, what is a greater indicator of success is how long does the weight loss last. Fad diets will rarely produce weight or health improvements that last long term.
Can people lose weight on the blood type diet? Yes, but it is not necessarily because they are following the right diet for their blood type. Notice the diet prescriptions for all blood types promote eating whole, unprocessed foods. This can often lead to weight loss and improvements in health long term. The blood type diet also encourages exercise, which is an important piece of health results.
If people are following the blood type diet and they believe it improves their health, there is probably no reason they need to stop. However, their positive health effects are probably not related to the diet being right for their blood type; it’s much more likely they’re following a healthier diet and lifestyle than before.
Nutrigenomics – How diet impacts genetics
While there are not significant studies to date that back up the claims of the blood type diet, the area of nutrigenomics is a fast growing field. Nutrigenomics, or also called nutritional genomics, is a field of research looking at how diet impacts someone’s genetic expression. There is still much to be uncovered of how food we eat impacts our health by interfering with genes.
It could be that people with a certain genetic make-up could benefit from following a specific diet that varies from people with a different genetic make-up. In the future, diets may be individually tailored in large part based off someone’s genetics. While basing diet off genetics is different than blood type, the idea is somewhat similar. As researchers learn more about this field, it could have a direct impact on changing food choices.
The organization Science Based Medicine cautions that there is currently not enough known about nutrigenomics to “diagnose” individual prescription diets based on genetics. Be wary of companies that are claiming to provide genetic testing for diets. The Science Based Medicine website claims “the field is not yet ready for the marketplace”.
The blood type diet was created from Dr. D’Adamo based on his theory of how blood types have evolved in the human race over the centuries. He claims if people living in the current age eat similar to ancestors when the blood type was introduced, health improvements and weight loss can happen. His website and book suggest what to eat based on your blood type and what type of exercise would suite you best.
Some people may have had weight loss success or improved health by following this diet, but is it because they were eating right for their blood type? According to peer reviewed research, probably not. There is no evidence of validity to the claims made about the blood type hypothesis, as concluded by two large peer reviewed research studies.
The diet plans no matter what your blood type promote eating unprocessed, whole foods and exercising in some capacity. This can give health benefits regardless of your blood type. Although no research as of yet suggests a link between diet and blood type, the area of nutrigenomics is growing. In the future, diet recommendations may be made based on someone’s genetics. However, researchers are quick to say the nutrigenomics research is not ready yet for extrapolating to the general public; more research is needed.
References used in this article