Blood Group Dieting: Fact or Fiction?
As a dietetic intern, I encounter individuals desiring to lose weight or simply achieve optimum health, who have read widely about various kinds of diets. One popular diet they frequently mention is the blood group diet. This particular diet instructs its followers to eat or restrict intake of foods based on their blood type (blood group) in order to achieve weight loss or optimum health. I have also watched TV programs where “experts” who have been invited to speak on nutrition and weight loss make reference to this type of diet. Since many followers are being won over in this country, it will be helpful to take a closer look at this diet.
Origin of the blood group diet
The blood type diet comes from the evolutionary theory of blood groups, first proposed by William C. Boyd. It states that our blood types have evolved in the same way as our species. In other words, we can draw a line from the earliest blood type, O, through history to the most recent, AB. The naturapathic doctor Peter D'Adamo took this theory and expanded it. He researched for many years, the connection between food and blood types, and wrote a best selling diet book called "Eat 4 Your Blood Type". Dr D’Adamo believes that because blood types evolved at different times throughout history, we should eat a diet based on the types of foods our ancestors typically ate at the time when our blood type was first recognized. Peter D'Adamo believes that, each blood type has different levels of stomach acid and digestive enzymes and according to him, this variation creates a difference on how food is digested and absorbed, and how fat is metabolized. None of these claims however have been substantiated scientifically. In other words the principles of this diet are not based on any credible scientific evidence and are largely theoretical.
Summary Of Recommended Eating Patterns For The Various Blood Groups - Blood Type O Diet (The Hunter)
This is the earliest blood group, associated with the hunter-gatherer ancestors. According to the diet, type O individuals tend to be muscular and active as a result, engaging in intense physical exercise is fundamental to the health of those in this blood type. Type O dieters are required to stick to a high-protein diet heavy in meat but light on vegetables. Dairy (e.g. milk and cheese) and wheat products will allegedly lead to weight gain and should be avoided if possible. Vegetables such as cabbage, brussel sprouts and cauliflower will also allegedly inhibit blood group O individuals’ thyroid function leading to fatigue and weight gain, hence they must be avoided. Coffee is also a strict no. - Blood Type A Diet (The Cultivator)
Type A evolved when humans began to build settlements and cultivate the land. The Type A diet therefore moves away from meat and emphasizes vegetables. Carbohydrates are fine, but meals should be very low fat. Dairy is also to be avoided, but coffee is beneficial. Type A should ideally adhere to a strict vegetarian diet of complex carbs, fruits and vegetables. Type A allegedly has trouble digesting any type of animal protein, including dairy, so protein must be obtained from nuts, seeds, legumes and soy-based products such as soya chunks. Calming exercises are thought to be best for blood type As such as yoga or golf. - Blood Type B Diet (The Nomad)
Blood type B supposedly evolved at a similar time to A, but is associated with a nomadic lifestyle and the herding of livestock. Dairy products are therefore an important part of this diet, along with a limited amount of meat. The only foods that need to be avoided are processed foods, although nuts and seeds are not recommended and only small amounts of carbohydrate-rich foods should be eaten. When it comes to exercise, Dr D’Adamo recommends activities that have a mental component, such as hiking, tennis and swimming. - Blood Type AB Diet (The Enigma)
Blood type AB is the most recently evolved blood type, and as you might expect, its a combination of diets A and B. It offers the most balanced diet compared to all the other blood types, with a mixture of dairy, vegetables and meat. In the same vein, blood type ABs should combine calming exercises with moderately intense activities.
The Pros and Cons
Let’s start with the pros. The blood type diet recommends eating fresh, natural foods and so can help you de-junk your diet by cutting out processed foods, takeaways, alcoholic drinks, chocolate and too many cups of coffee. The blood type diet is also inexpensive and will only require that you buy the book or even do some research online.
The cons are many. First of all adherents would need a blood test to find out their blood groups if they don’t already know it. Furthermore the restrictions are confusing to say the least, even for literate populations in the western world, how much more in Ghana where literacy levels are low in majority of the populace. Some appreciable level of literacy is mandatory if you are to understand and appreciate the rationale for the restrictions. Mealtimes may also be impossible if everyone in the family wants to follow the diet, but has a different blood group. While you’ll probably lose weight (purely as a result of food restriction and cutting calories and not because of how it works with your blood type), it could also affect your health in the long term as the food restrictions for the various blood types could lead to nutritional deficiencies.
To follow or not to follow
As with any form of diet, talk to your doctor or a dietitian first, especially if you suffer from chronic, diet-related health problems and don’t just rely on anecdotal evidence. Look at the scientific proof before you make a decision. Any diet that tells you not to eat fruit or vegetables in a wide variety every day (as is the case for blood type O) is a bit suspect. Remember, nothing replaces a good balanced diet that is low in saturated fat and sugar, provides the required daily intake of fibre, calcium and other essential nutrients. Your blood type makes no difference in this regard. No dietitian worth his/her salt will be talking about blood group dieting in this day and age of evidence-based medicine. The consuming public must get discerning in order not to be led astray by poorly qualified individuals.
To conclude, the words of Julliette Kellow (a well respected UK registered dietitian) summarize it all. “Nevertheless, based on Dr D’Adamo’s theory, I’m looking forward to the evolution of blood type F! People with blood type F will need lots of fast food, takeaways, pizza, sugary snacks, crisps and chocolate to remain in tune with their environment. After all, if the theory is correct, surely that’s what we can expect, based on what many of us now eat in the 21st century!”
Author: Laurene Boateng [Email:healthquestdietitian@gmail.com]
(The writer is a dietetic intern (MPhil Dietetics) of the School of Allied Health Sciences, College of Health Sciences, University of Ghana.)
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