The blood group diet: fact or fiction?

A diet that you truly enjoy and makes you feel good, while allowing you to maintain a healthy body, seems like the best of both worlds.

And as each individual is unique, in terms of food preferences, habits and tolerances, it makes sense that personalized diets are now recommended by most health experts – of which dieticians do exactly that!

However, these motives could explain why many people have chosen to base their dietary choices on their blood type, in the hope of reaping its perceived benefits, including living a long, healthy life. But what does it mean to eat for your blood type?

Most importantly, is there evidence that this approach works and is beneficial? Let’s find out.

What is the blood group diet?
The blood group diet is an eating plan which calls for consuming certain foods and avoiding others, based on the claim that your diet should be in line with your blood type. This is because the body responds differently to various foods depending on your blood type.

This diet has been popular since 1996 when it was created by an American naturopathic doctor named Dr Peter D’Adamo. His book, “Eat right 4 your type”, is still an incredibly successful book, selling millions worldwide.

Dr D’Adamo believes that your blood type is a significant key to understanding your unique individuality and helps to tell the story of human evolution.

According to him, blood types evolved with the evolution of man, and each blood type represents the genetic traits of your ancestors.
It also indicates which diet your ancestors of the same blood type ate to survive – thus showing which foods are best for your body and which foods aren’t.

Another central theory of the blood group diet has to do with a group of proteins found in many foods known as lectins. These proteins bind to carbohydrate molecules found on red blood cells.

Dr D’ Adamo argues that some lectins specifically target the different blood types. Eating the wrong types of lectins, which is incompatible with your blood type, could cause your red blood cells to clump together (or agglutinate) when such lectins bind with the carbohydrate molecules on the cells.

This consequently can cause havoc in various parts of the body. Hence, avoiding this agglutination by eating “rightly” might enable people to prevent health problems like cancer, heart and kidney diseases, and even manage their weight better.

Overall, proponents of this diet suggest that following the blood group diet has many benefits including:
•  Weight loss

•  Enabling the body to digest food better

•  Prevention of diseases

•  Slowing down the ageing process

•  Having more energy

•  Feeling better and boosting overall well-being

How does the diet work?
You first have to know your blood type based on the ABO blood system: either A, B, AB or O. Next, plan your meals around foods you’re encouraged to eat for your blood type, while avoiding those that are believed to be problematic.

Here’s a brief outline of the blood type diet:

Type A
The type A diet is steered towards a predominantly fresh, organic vegetarian (plant-based) diet.

Foods allowed: most vegetables and fruits, soybeans, whole grains (rice, wheat, millet, corn etc.), nuts and seeds.
Poultry (specifically chicken and turkey), most fish, snails and eggs are to be taken in limited amounts.

Foods to avoid: red meat (beef, pork, etc.), shellfish (shrimps, oysters, crabs etc.), dairy (milk, cheese, yoghurt etc.), yam, potatoes, plantain, cashews, kidney beans, mushrooms, cabbage, tomatoes, peppers, banana, pawpaw, orange, mango, sugary foods, caffeine and alcohol.

Exercise: 30-45 minutes of light-to-moderate, calming exercises like yoga at least three times weekly.

Type B
This type is said to benefit from “everything in moderation”, and are advised to eat a balanced, omnivorous diet, allowing for a more varied food intake from both plants and animals.

Foods allowed: red meat, organ meats, low-fat dairy, eggs, most vegetables (especially greens), beans and other legumes, fruits, fish, rice, millet, yam, potatoes, cocoyam and plantain.

Foods to avoid: chicken, shellfish, corn, wheat, sorghum, lentils, avocado, tomatoes, nuts and seeds.
Exercise: moderate-intensity exercises like walking and tennis.  

Type AB
People with this blood type are encouraged to eat a well-rounded, omnivorous diet from a relatively wider variety of foods, making this diet the least restrictive.  

Foods allowed: fish, turkey, eggs, snails, rice, oats, wheat, millet, certain beans (e.g. soybeans), nuts, tubers (yam etc.), plantain, low-fat dairy, most fruits and vegetables (especially greens).

Food to avoid: red meat, chicken, smoked and cured meats (e.g. sausage, bacon etc.), shellfish, other beans, corn, mango, avocado, banana, orange, peppers, caffeine and alcohol.

Exercise: A combination of both calming and moderate-intensity exercises, e.g. 45-60 minutes of walking at least twice weekly balanced with daily stretching exercises.

Type O
Type Os are to consume filling high-protein, with a somewhat low-carb, high-fibre diets.

Foods allowed: lean, organic meats and poultry, seafood, eggs, snails, peas, seeds, rice, millet, most tubers, fruits and vegetables.
Food to avoid: wheat and wheat-based products (e.g. bread, pasta etc.), corn, dairy, plantain, Irish potatoes, beans, groundnuts, cashew, avocado, orange, caffeine and alcohol.

Exercise: 30-45 minutes of high-intensity, aerobic exercises like jogging and cycling at least four times weekly.
In addition to eating specific foods for your blood type, the creator of this diet recommends his different but specific supplements to make sure you meet all your nutrient needs and achieve your weight goals.

Also, calorie-counting is considered unnecessary, with claims that as long as you’re eating the right foods, weight loss should come naturally.

There isn’t any specific timing for meals or fasting periods required for this diet plan. However, it advises against drinking water or other beverages with meals as it will dilute the natural digestive enzymes, thereby making it more difficult to digest foods.

The pros and cons
Starting with the positives, the diet advocates that everyone, irrespective of blood type, should eat mostly fresh, whole and natural foods, whilst cutting out processed foods and alcohol.

And we know that a variety of natural foods contain the nutrients and fibre our bodies need to stay fit. This practice may help reduce the risk of many chronic health issues like high blood pressure, glucose and cholesterol levels whilst promoting weight loss.

The diet also encourages people to focus holistically on their overall well-being, by including regular exercises and stress reduction together with eating healthily.

Overall, the diet plan emphasises the importance of a personalised nutrition plan, meaning that meeting the nutritional needs of individuals should vary from person to person, rather than a “one-size-fits-all” approach.

And if nothing else, it creates self-awareness about eating habits and makes you think twice about your food choices.     
Now to the negative side of things. Firstly, there’s generally a lack of scientific evidence regarding if and how the diet works, and thus, supporting or recommending it.

Although some claims have been made, it hasn’t been proven that your blood type determines how your body reacts to certain foods and that its adherence could improve health.

For people who see results, it could have been circumstantial or based on a factor other than blood type.
Limiting the intake of processed foods, as advised by this diet, for example, would definitely produce good health outcomes, irrespective of your blood type.

Cutting out food groups is an easy way to reduce calories and can lead to some weight loss, as with the blood group diet. But in eliminating some foods that are considered crucial for good health, you’d also be taking out vitamins, minerals and other needful nutrients.

Eventually in the long-term, you could experience nutritional deficiencies when following this diet plan.
Imagine if your favourite food is fufu, and you’re told to stop eating it because of your blood type – what a struggle that would be! These potentially make the diet hard to follow, expensive and can cause a person to feel socially isolated.

The diet also fails to consider health challenges an individual may have (e.g. diabetes, hypertension, allergies etc.), hence could disrupt medical treatment plans when followed.

Regarding lectins, there’s actually evidence that a small percentage of lectins in raw, uncooked legumes (e.g. beans) can cause agglutination on red blood cells. However, lectins in food aren’t blood-type specific.

Overall, this fact may be irrelevant because most legumes are soaked and/or cooked before consumption, which destroys the lectins.
Bottom line: the foods recommended for a particular blood type aren’t necessarily the best, health-wise. Instead, improve your health by following scientifically-proven, nutritious eating guidelines, non-specific to your blood type.

Whatever your health goal is, it has to be reasonable and sustainable – the blood group diet may not be so. Further research is needed to support the health claims associated with this diet.

In conclusion, could eating a diet based on your blood type – A, B, AB, and O – help you get healthier? That’s the idea behind the blood group diet, created by the naturopath Dr. Peter D’Adamo.

Is the diet indeed a fact or just one of those fictitious, fad diets? In short, it’s somewhat complicated.

I don’t doubt that people have experienced positive results by following the diet. Nonetheless, it doesn’t mean that this was related to their blood type.

The diet encourages real, healthy foods, which is a huge step up from processed, junk foods. Maybe the reason for the health benefits is simply because these people are eating healthier food than before.  

There’s little to no science to back up the diet. Nutrition experts don’t also support or recommend it for achieving nutrition or health goals. You mustn’t rely on popular yet unproven diets to guide your eating habits and food choices.

There are cheaper, safer and more evidence-based ways to change your diet to improve health. That being said, if you’re considering going on any diet, talk with your dietician first to determine the best course of action for you that’s based on scientific evidence, as well as your personal preferences and health goals.
Stay safe!

The writer is a registered dietician and a member of the Ghana Academy of Nutrition and Dietetics
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