Have you ever wondered whether your blood type makes a difference to your health?
It certainly makes a difference when it comes to transfusions, and studies show some blood groups are more at risk of certain diseases—but there’s also an interesting theory that eating foods compatible with your blood type can make you healthier.
RELATED: What Are the Blood Types Really for?
What’s the O Blood Type Diet About?
There are eight different blood groups: A, B, AB, and O; each group can be either RhD positive or RhD negative.
Your blood group is determined by the genes you’ve inherited from your parents, and this stretches right back to your stone-age ancestors.
The blood type diet is a theory that your blood group reveals the dietary habits of these predecessors.
The “Eat Right For Your Type” diet was created by Peter J. D’Adamo. He suggests that O was the first blood type. Type O has been traced back as far as Cro-Magnon man in 40,000 BC (although there is debate over whether type A is the earliest blood type).
These early type O humans ate a hunter-gatherer diet of animal protein, but as they moved into a society that put down roots and farmed crops, their blood evolved into type A to help them digest carbohydrate, fruits, and vegetables.
Rarer type B blood types are thought to descend from the ancient nomadic tribes that consumed dairy from their herds.
His theory suggests that blood type O positive and O negative people have hunter-gatherer digestive systems that handle meat and fish better than carbs, grains, and dairy.
RELATED: Eating for Your Blood Type—B+ & B-
Does the O Blood Type Diet Work?
The O blood type diet has no scientific backing. There’s no medical research that indicates eating an O positive blood type diet or an O negative blood type diet will improve your health.
However, the idea is popular, and followers say they feel better adapting their diet to their blood type. Further, there are studies that show your blood type can have an effect on your health.
Eating for Your Blood Type: Type O
Type Os are able to eat more animal protein that blood types A, B, and AB because they have more hydrochloric acid in their stomach and secrete greater amounts of the intestinal alkaline phosphatase—and a lipoprotein called ApoB48.
These advantages make them better at digesting animal protein and fat and help them metabolize cholesterol more efficiently. D’Adamo also says this also increases their ability to heal their digestive tracts.
Lectins are proteins in food that bind to our blood cells and cause a chemical reaction. D’Adamo suggests this can cause difficulties if the food is not one your blood is easily able to digest. In Type Os, this can mean that metabolizing dairy or carbohydrate is difficult.
Type Os would have no issues with animal protein lectins, but they might struggle with dairy or grain-based lectins, which are more easily converted into fats and triglycerides and can cause inflammation.
What to Eat on An O Blood Type Diet
People with type O blood should focus on a high animal protein diet with vegetables, fish, and fruit. They should limit grains, dairy, beans, and legumes.
Good foods to eat include:
- Meat, particularly lean meat—but not processed like bacon or sausages
- Fish like cod, herring, and mackerel
- Seafood with iodine
- Fruits, particularly plums, prunes, and figs
- Vegetables, in particular, leafy greens like kale
Because blood type Os digest meat more easily, an entirely vegetarian diet is not advised.
D’Adamo advises that alongside a blood type diet, type Os should exercise vigorously.
Aerobic exercises like running, cycling, and weight training suit blood type O, as they are potentially more prone to the stressful fight-or-flight response of our hunter ancestors. This can cause bouts of excessive anger, but dopamine from brisk exercise is an excellent way to counteract it.
The more they work out and the higher the intensity, the better the blood type Os will feel.
Foods to Avoid on An O Blood Type Diet
D’Adamo recommends that you avoid cereals, grains, dairy, legumes, and beans.
Specific foods to avoid include:
- Wheat and corn
- Legumes (podded beans)
- Beans, especially kidney beans
- Dairy, such as cow’s milk
He also suggests type Os avoid coffee, as their higher levels of hydrochloric acid could lead to peptic ulcers. Green tea is recommended instead, as it’s less irritating.
I’m O Negative—Does That Make a Difference to the Diet?
No, it doesn’t make a difference if you are O positive or O negative.
Positive blood has a protein on the surface of its red blood cells known as the Rhesus antigen. If you don’t have this protein, your blood is rhesus negative.
Around 85% of people in the USA have positive blood. It’s the most common type worldwide, but it doesn’t affect the blood type diet if you are rhesus negative.
You should eat based on whether you are blood type O, A, B, or AB.
Are There Any Risks?
There’s no evidence that this diet is risky, but it does encourage eating a lot of animal protein and fewer beans and grains, which can lead to health problems associated with a reduced fiber intake.
Should I Follow the O Positive Blood Type Diet?
If you want to follow the O blood type diet and don’t have any dietary needs, such as a sugar-controlled diabetic diet, then you may find it beneficial.
It’s important to make sure you eat all the necessary vitamins and minerals, or you run the risk of a deficiency that can harm your health more than eating certain blood type foods.
If you’re blood type O and fancy this diet, perhaps try it out for a few weeks, gradually introducing the right foods and phasing out the ones to avoid. After that time, reassess how you feel.
If you’re unsure whether a new diet is good for you, it’s best to seek professional medical advice first.