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Expert Q&A

Does your blood type affect your diet?

By CJ, Ohio

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Hi, Dr. Melina. I was wanting your opinion on eating for your blood type. I am reading a book about it and wanted to know your thoughts.

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Diet and Fitness Expert Dr. Melina Jampolis Physician Nutrition Specialist

Expert answer

Hi, CJ. I get asked about this diet quite often so I decided to do a little bit more research on the topic and go straight to the author, Peter J. D'Adamo, who is a naturopathic doctor, to get his explanation.

D'Adamo believes that based on your blood type, you react differently to substances called lectins, which are present on the surface of most foods. If you eat foods to which you react adversely, the negative response (which includes inflammation) can trigger different diseases based on your blood type as well as fatigue, poor digestion and weight gain.

In addition, he believes that there are differences in our body chemistries based on blood type that determine what foods we digest optimally.

This is not so much a diet but rather a lifestyle. Adopting the proper diet for your blood type, according to D'Adamo, can lead to weight loss if you follow a lower calorie version, but to maintain the health benefits, the diet must be followed for good.

You don't have to follow his diet perfectly, he notes. He recommends easing into it and essentially following it as strictly as necessary for your particular health concern, allowing for even more individual variability in his dietary approach.

His approach also involves four unique approaches to exercise based on your blood type, citing differing responses to stress based on your blood type.

D'Adamo notes that in his experience, eight out of 10 people report satisfaction with the diet, with the predominant benefits revolving around gut health, immune health (fewer infections) and weight loss. He suggests trying it for several months to see if you benefit.

The more symptoms you have that are potentially associated with diet, especially gastrointestinal and food allergy-type symptoms (diarrhea, bloating, fatigue), the more closely you should follow your recommended way of eating.

The diet for type O, the most common blood type, is a high-protein diet that limits wheat and encourages vigorous exercise. The type A diet, the second most common blood type, is a low-fat vegetarian diet that encourages gentle exercise such as yoga and golf. The B type diet is more varied and encourages moderate exercise, and the AB diet is a blend of type A and B.

Let me start with the pros of this diet. I think it is critical to realize that there is no one-size-fits-all approach to dieting for optimal health and weight loss.

I commend D'Adamo for recognizing this fact. In addition, I think we are seeing an increase in food allergies, intolerances and inflammatory-related diseases, so looking more carefully at specific foods which certain people may be responding poorly to is a good idea.

Food intolerance/allergy testing is expensive and in most cases not completely reliable so doing a diet elimination trial for certain foods is a reasonable and economical approach.

That being said, I'm not convinced that lectin and blood type are the answer. This may be a contributing factor in some cases, but I think D'Adamo would agree that there is more to the story. I believe that the huge increase in processed food, food additives, chemically and genetically modified food, and fast-food consumption in this country are likely far more of the culprit in both poor health and weight gain for most people than blood-type associated food responses.

While I think that all of the diets, with some effort, planning and modification (less red meat), could be relatively healthy and reasonably balanced (they all recommend ample amounts of fresh fruits and vegetables, which most Americans should be eating more of), I think the diets are complicated, not practical in some cases (some foods are hard to find and unfamiliar to the average person), and can be challenging (for example if families are made up of numerous blood types).

The suggested weight loss versions of the diet, particularly for type O, would not be healthy and balanced. Also, for the O type diet, D'Adamo states in his book that the success "depends on your use of lean, chemical-free meats, poultry and fish."

I certainly agree this is healthier, but this can be expensive, and I'm concerned that if people eat the recommended amounts of red meat and cannot afford organic, grass-fed beef and chicken and wild fish, this diet could negatively affect their health and could increase their risk of heart disease and cancer.

The O diet also eliminates wheat gluten, which limits a great deal of the unhealthy, processed foods that cause inflammation and weight gain. Eliminating refined grains and sugar baked goods alone may lead to improved health and weight loss without the complicated food prescriptions for many.

As far as exercise is concerned, while his explanation is interesting, I'm not convinced of his argument. I'm sure that based on personality types, athletic prowess, habits and lifestyle, some people do better with different types of exercise.

But from an overall weight loss/maintenance, heart health, and bone health standpoint, I think the focus should be on getting the recommended amounts of aerobic exercise (150 minutes per week of moderate or 75 minutes per week of vigorous) and strength training twice a week.

There is good research showing the benefits of tai chi and yoga for heart health, so many may want to consider integrating this type of exercise as well on a regular basis.

My conclusion: If you feel as if you have really improved your diet (i.e. you have cut fast food and processed food, reduced your intake of added sugar and solid fat, and added plenty of fresh vegetables and fruits) and yet you are still struggling with weight, stomach or bowel problems, inflammatory conditions or food allergies, you may want to try adopting the basic principles of this diet for a few months.

I recommend checking in with your doctor after a few months to make sure that your blood sugar and cholesterol have not been negatively affected. As with any diet, if you lose weight or feel better, you must maintain these principles and not simply return to your old way of eating.

According to D'Adamo, unless you have food allergies or gut inflammation, "it won't hurt most people to occasionally eat a food that is not on their diet" so this really should be viewed as a lifestyle if adopted. As a medical doctor trained in Western medicine, this approach is harder for me to embrace fully, but as I learn more about alternative medicine, I feel that I must remain open to other concepts that may not be completely proven in our Western medical model, especially when it comes to nutrition and diet-related topics that are particularly challenging to prove convincingly.

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