Blood Type O Diet: What to Eat and What to Avoid

Blood Type O Diet: What to Eat and What to Avoid

The Blood Type Diet was developed by Dr. Peter J. D’Adamo, the author of the bestsellers “Eat Right for Your Type” and “Live Right for Your Type”. The diet is based on the principle that chemical reactions occur between the foods you eat and your blood type. According to D’Adamo, if you follow a diet designed for your blood group, your body will digest food more efficiently, you’ll lose weight, have more energy, and have a better general health.

According to D’Adamo, the blood type O diet is beneficial for people with O positive blood type as well as people with O negative blood type. Because blood type O is the most common blood type, I am going to look at the Blood Type O Diet and discuss what foods you should eat and what you should definitely avoid. At the end of the article you will find what critics say about this type of diet.

What exactly is Blood Type O?

Your blood group is identified by antigens and antibodies in the blood.

Antibodies are part of your body’s natural defenses against invading substances such as germs. Antibodies recognize anything foreign in your body and alert your immune system to destroy it.

Antigens are protein molecules found on the surface of red blood cells.

Blood group O has no antigens, but both anti-A and anti-B antibodies. As group O red blood cells don’t have any A or B antigens, it can safely be given to any other blood type group (A, B, AB).

What is the difference between O positive and O negative blood type?

Red blood cells sometimes have another antigen, a protein known as the RhD antigen. If this is present, your blood group is RhD positive. If it’s absent, your blood group is RhD negative.

A person with blood type O can have either O positive (O+) blood type or O negative (O-) blood type.2 The blood type O positive contains the RhD antigen but the blood type O negative doesn’t contain the Rhd antigen.3 The majority of people have O positive blood type.

What is the Blood Type O Diet?

According to Dr. D’Adamo, people with blood type O have more stomach acid which makes it easier to digest meals that contain protein and fat. Therefore, a blood type O diet contains more protein sources like red meat, poultry and fish.

However, a person with blood type O should limit their intake of grains, beans, and legumes and definitely avoid wheat and certain leafy vegetables. The reason for this is due to a compound called lectins.5

Lectins help your immune system to fight disease. However, according to Dr. D’Adamo, if you eat food containing lectins that are incompatible with your blood type, this can cause inflammation in the body and make the immune system become overactive, which can lead to autoimmune diseases.4

It has to be said that the blood type diet is not without its critics, and not all doctors agree with the health benefits of the Blood Type Diet. At the end of this article, I will discuss what some of the critics have had to say, and look at the evidence that Dr. D’Adamo has presented to refute their claims.

Let’s look at the best and worst foods for people with blood type O (O positive or O negative).

What to Eat and What Not to Eat on the Blood Type O Diet

People in the O blood group should follow a strict diet of certain foods. This means that it’s important to know what foods you can definitely eat and what foods are strictly off limits on the blood type O diet.

Lean Meats

For people in the O blood group, most lean meats that are organically fed are recommended to include in the diet.

The best types of protein sources that have a beneficial effect for people with blood type O positive and O negative are beef, veal, lamb, venison, and also most poultry. If you don’t eat meat, but prefer seafood there is plenty of choice of fish that you can enjoy. For example, cod, trout, herring, tuna, and mackerel are excellent foods to eat on the O blood type diet because they are a good source of iodine which is necessary for a healthy thyroid gland.

What meats to avoid

There are some meats that must be avoided if you are following the type O diet. These include most processed foods like bacon; in fact, any pork products are a definite no-no for people with O positive or O negative blood type. From seafood products, you should definitely not eat octopus and salmon roe (caviar) if you have blood type O.

So, from protein sources, there is a wide variety of meats and seafood to choose from for people in the blood O group.

Beans and Legumes

People who have blood group O need to be careful with the type of beans and legumes that they consume. Some beans are excellent for the O type blood group; however other legumes should be avoided. According to Dr. D’Adamo, people with O type blood often suffer from thyroid disorders and certain beans can either help the thyroid or slow down the thyroid.4

If you follow the blood type O diet you can include black beans, adzuki beans, and green (string) beans. Beans are also a valuable source of proteins and many beneficial nutrients. These types of beans help the thyroid gland to produce enough thyroid hormone for the body.

What beans and legumes to avoid

There are some beans and legumes which should be completely avoided by people who have blood type O. These are soybeans, lentils, green peas, and peanuts, including peanut butter. These foods are best avoided by people with O type blood because they are either harmful to you or provide no benefit at all.


Many fruits are beneficial for people who are in the O blood group. This is because some fruits help to regulate the stomach acid, which people with blood type O tend to have much more of.

Some of the best fruits for people with O blood group are plums, figs, and prunes because they help to lower stomach acid and keep your digestive system working effectively. Berries like raspberries, gooseberries, and cranberries can be eaten occasionally.

What fruits to avoid

Although most fruits are a good source of vitamins, there are a number of fruits that you should not eat if you are in the O blood group. The fruits to avoid in the blood type O diet are oranges, blackberries, strawberries, kiwifruit, and melons. This is because these negatively affect your metabolism or enhance toxins of other foods if you have O positive or O negative blood type.


There are many vegetables that are beneficial if you follow the O type diet. Leafy green vegetables are the best kind for people with O type blood because they are rich in vitamins and minerals and help to reduce blood clotting problems.

According to the blood type O diet, you can eat plenty of green leafy lettuce, kale, broccoli, okra, red peppers, and ginger root. These will help to keep you healthy and maintain your proper weight.

What vegetables to avoid

Other types of vegetables like cabbage, cauliflower, and Brussels sprouts, should definitely be avoided because they can affect thyroid hormone production. Also, you shouldn’t eat mushrooms and pickled vegetables if you are on the O blood group diet because they can cause inflammation in the digestive lining.

Dairy Products on the Blood O Diet

For people with blood type O (negative or positive), most dairy products should be avoided. This includes yogurts and most cheeses and eggs. However, small amounts of butter and mozzarella can be consumed on the blood type O diet.

Other Tips for the Blood Type O Diet

Apart from what I’ve already mentioned about what to eat and what not to eat on the blood type O diet, there are some other dietary restrictions:

  • It is also advisable for people in the O blood group to completely avoid grains including wheat bread because the gluten in grains interferes with how the body processes insulin.
  • According to D’Adamo, rice, spelt, amaranth, quinoa and millet can be beneficial if you have O blood type.
  • Most alcoholic beverages and caffeinated drinks are a big no-no for people with blood type O. However, you can drink wine, water, and tea.

A person with O blood type who follows the blood type diet can deal with stress and anxiety better and reduce the risk of dependency on certain substances like drugs and alcohol. This is because the blood type O diet is claimed to balance levels of dopamine and other important brain chemicals.4

If you want to find out information on diets for the other blood types and the benefits that you can get from them, then please read my article on how to eat right for your blood type.

Is the Blood type O Diet for Everyone? What the Critics Say

If you conduct an online search for the Blood Type Diet, you will find that there is much controversy about the effectiveness of following a diet purely based on your blood type. Some people say that it only helps a person because it cuts out processed food and increases the consumption of vegetables. Very often the words “debunked”, “skeptical”, and “quack” are used. However, is criticism of the blood type diet warranted?

In every case Dr. D’Adamo has refuted his critics’ claims with his own scientific proof. For example, he points out that one criticism is about the way lectins affect the blood. An article on the Weston Price Website dismisses the role that lectins have on the blood stream. However, as Dr. D’Adamo points out, on the very website that dismisses lectins, the author claims that you should avoid soy because of dangerous hemagglutinating lectins. So, it seems that there is some hypocrisy in the claims against the Blood Type Diet.

Dr. D’Adamo also points out that he is accused of offering very little scientific evidence for the Blood Type Diet. However, in his responses he always points to scientific research to back up his claims on the benefit of the Blood Type Diet.

Is the Blood Type O Diet suitable for you? It may not be for everyone, however, many people have benefited from following a diet according to their blood group.

Read my other article to learn what to eat for A, B, and AB blood types: How to Eat Right for Your Blood Type

Article Sources

Healthy and Natural World