Key takeaways

The O positive blood type diet suggests people with different blood types should eat differently, but the scientific evidence supporting this theory is limited.
Lean meats, fish, vegetables, fruits, and olive oil are recommended for people with O positive blood, according to this dietary approach.
Theoretically, based on this diet, people with O positive blood may want to limit wheat, corn, legumes, kidney beans, dairy products, caffeine, and alcohol.
Supplements such as vitamin D, omega-3 fatty acids, and probiotics may be beneficial for people with an O positive blood type.

In this article:

What is the best diet for O positive blood?
Foods for O positive blood
Foods to avoid for O positive
Supplements for O positive blood type
The science behind blood type and diet

In this article

What is the best diet for O positive blood?
Foods for O positive blood
Foods to avoid for O positive
Supplements for O positive blood type
The science behind blood type and diet

The blood type diet, created by naturopathic physician Peter D’Adamo, ND, suggests that eating a diet specifically aligned with one’s blood type can provide benefits such as improved digestion, increased energy levels, disease prevention, and weight loss. In his book Eat Right 4 Your Type, he outlines different eating plans for the other blood types: A, B, AB, and O.

Each blood type is identified by the presence or absence of certain molecules called antigens on the surface of red blood cells. The basic premise of the diet is that a person’s blood type determines their ability to digest and metabolize certain foods. For example:

Blood Type A: Individuals with type A blood are advised to follow a vegetarian diet or plant-based diet full of fruits, vegetables, whole grains, legumes, and tofu with minimal meat, dairy, and processed foods.
Blood Type B: D’Adamo recommends lean meat, fish, dairy products, fruits, vegetables, and whole grains for this blood type. Corn, chicken, wheat, and lentils should be avoided, according to his suggestions.
Blood Type AB: People with AB blood are advised to consume a combination of type A and B foods, such as tofu, seafood, dairy, fruits, vegetables, and whole grains.
Blood Type O: Individuals with the O blood type are recommended to eat a high-protein diet incorporating lean meats, fish, and protein while limiting grains, dairy, and legumes.

Additionally, D’Adamo says that people with O positive blood should incorporate a variety of fruits and vegetables, especially dark leafy greens, into their diet. Healthy fats like olive oil are preferred for cooking and salad dressing. However, research supporting these claims is limited.

What is the best diet for O positive blood?

Dr. D’Adamo claims that your blood type impacts how you react to proteins called lectins that are found in certain foods, causing digestive and hormonal issues. He also proposes that people with different blood types are susceptible to different chronic diseases, and eating a particular way can help reduce these risks and enhance your overall health. For people with O positive blood, he recommends a high-protein diet that limits grains, beans, and dairy.

However, there is no scientific evidence to support this claim; the blood type diet has been largely debunked, says Paunel Vukasinov, MD, a dual board-certified internist and obesity medicine specialist at the Medical Offices of Manhattan in New York, New York.

For example, the 2020-2025 Dietary Guidelines for Americans promote a plant-based diet rich in fruits, vegetables, whole grains, and legumes and low in red and processed meats, saturated fats, and alcohol. A private organization with a mission of encouraging plant-based diets, the Physicians Committee for Responsible Medicine, suggests that eating a high-protein, low-carbohydrate diet (high in saturated animal fats) is not ideal due to the increased risk of health conditions such as Type 2 diabetes, weight gain, and heart disease.

When developing a diet, other important factors to consider are beyond blood type. “Nutritional needs vary widely among individuals and are influenced by factors such as age, gender, activity level, health status, medical conditions, and genetic predispositions,” says Michelle Routhenstein, a registered dietitian at EntirelyNourished.com.

“Ultimately, it’s important to emphasize that choosing a healthy way of eating that best fits your life and that you can stick with for the long-term is the right approach,” says Dr. Vukasinov.

Foods for O positive blood

According to D’Adamo’s book, the following foods are mainstays of the O blood type diet, which is gluten-free and high in protein. Intense aerobic exercise is encouraged.

Meat

D’Adamo believes that lean red meats such as beef, organ meats, and lamb are believed to benefit O positive individuals due to their high protein content. These meats are considered to be easily digestible and provide essential amino acids necessary for muscle growth and repair. Processed or fatty meats should be avoided, and eggs are neutral.

Fish

Fish rich in omega-3 fatty acids, such as salmon, mackerel, and sardines, is advised by D’Adamo for individuals with an O positive blood type. These fatty fish are believed to have anti-inflammatory properties and can help support heart health and brain function. Including fish in your diet can also provide a good source of protein and essential nutrients like vitamin D and B vitamins.

Vegetables

According to D’Adamo, individuals with O positive blood should focus on consuming a variety of vegetables, especially dark leafy greens like spinach, kale, and broccoli. These vegetables are rich in vitamins, minerals, and antioxidants. They are believed to support optimal digestion, boost immune system function, and provide essential nutrients for overall health.

Fruits

D’Adamo says that individuals with O positive blood should incorporate a variety of whole fruits into their diet, including berries, cherries, and figs. These fruits are believed to provide antioxidants, promote healthy digestion, and support immune function.

Olive oil

Olive oil is a healthy fat option for individuals with O positive blood, according to Dr. Adamo. It is rich in monounsaturated fats, which have heart-healthy benefits. It can also provide anti-inflammatory properties and support brain health. Incorporating olive oil into the diet can help add flavor to meals and provide essential fatty acids.

A sample meal plan on the diet might include:

Breakfast: Cooked oatmeal with fresh fruit and walnuts.
Lunch: Ground beef patty on a whole grain bun; salad with lemon and olive oil.
Dinner: Salmon with brown rice and spinach.
Snacks: Fresh berries and broccoli, pumpkin seeds, or Ezekiel bread.

Foods to avoid for O positive

Conversely, people with O positive blood should avoid certain foods. D’Adamo says these foods may cause digestive issues, inflammation, and other health problems for individuals with this blood type.

Wheat

Wheat and wheat products, such as bread, pasta, and pastries, should be limited in the O positive blood type diet. That’s because wheat contains lectins (plant proteins), which can be beneficial, according to a topic review, but that can interfere with the digestive system of individuals with O positive blood, according to Dr. D’Adamo. He says that lectins contribute to inflammation and digestive issues and interfere with nutrient absorption in the digestive tract.

Corn

Corn is another food that D’Adamo advises limiting in the O positive blood type diet. Similar to wheat, corn contains lectins that D’Adamo believes negatively affect individuals with O positive blood.

Legumes

Legumes, including beans, lentils, and peanuts, are also advised to be limited in the O positive blood type diet due to their lectin content. D’Adamo suggests choosing other protein sources, such as lean meats.

Kidney beans

Kidney beans are specifically mentioned as a food to be avoided in the O positive blood type diet. They contain a lectin called phytohemagglutinin, which can be toxic when consumed in large amounts or undercooked. D’Adamo says this lectin is particularly problematic for individuals with O positive blood.

Dairy

Dairy products like milk, cheese, and yogurt should be avoided on the O positive blood type diet. D’Adamo says that individuals with O positive blood may have difficulty digesting lactose, the sugar found in dairy products. Lactose intolerance can lead to digestive issues such as bloating, gas, and discomfort. Opting for dairy alternatives such as almond milk, soy milk, or coconut milk is recommended.

Caffeine

Caffeine should be limited, as D’Adamo believes that individuals with type O positive blood may be more sensitive to its stimulating effects. Excessive caffeine consumption can lead to increased heart rate, nervousness, and disrupted sleep patterns. D’Adamo suggests opting for herbal teas or caffeine-free alternatives.

Alcohol

Individuals with O positive blood may have a lower tolerance to alcohol and may experience its adverse effects more intensely, according to D’Adamo. Excessive alcohol consumption can potentially lead to liver damage, impaired judgment, and other health issues.

RELATED: High blood pressure diet

Supplements for O positive blood type

While the O positive blood type diet primarily focuses on food choices, certain nutrients are recommended for those with type O positive blood. Specific supplements are sold on D’Adamo’s website to address potential deficiencies of the diet, such as:

Prebiotics
Probiotics
Multivitamins containing vitamin A, vitamin C, and vitamin B12
Protein powders
Digestive enzymes
Seaweed supplements containing vitamin K, vitamin D, and calcium

The science behind blood type and diet

But does the blood type diet work? While Peter D’Adamo’s theory on blood type and diet is popular, the scientific evidence supporting the relationship between blood type and diet is limited and controversial.

For example, no research supports the idea that certain blood types are more sensitive to caffeine and alcohol or more likely to develop lactose intolerance. And because lectins are highest in raw foods, proper food preparation and cooking methods—like steaming, boiling, soaking, and deseeding—dramatically reduce their lectin content. What’s more, foods containing lectins are sources of important nutrients.

One 2014 study found that individuals who followed the blood type A-specific diet experienced improved cardiometabolic risk factors like BMI, blood pressure, blood sugar levels, and cholesterol. However, this applied to everyone who followed the diet regardless of their blood type. A 2013 research review concluded that no evidence exists to verify the health benefits of eating according to blood type.

The bottom line? “The theory that blood type influences optimal diet lacks validated scientific evidence,” says Routhenstein. Following restrictive diet plans based on unsupported theories, such as avoiding entire food groups like dairy or carbs based on blood type, can potentially lead to nutritional deficiencies and abnormal cardiometabolic metrics if not adequately assessed and tailored, urges Routhenstein.

Critically evaluating dietary recommendations is essential to ensure they are supported by science, as unproven fad diets can potentially lead to harmful health outcomes, advises Dr. Vukasinov. “Proper evaluation ensures that recommendations support balanced nutrition, providing essential vitamins, minerals, proteins, fats, and carbohydrates necessary for overall health,” he says, adding that recommendations based on rigorous scientific research are more likely to be effective and safe.

It is important to approach diet and health in a personalized manner and consult with a healthcare provider, such as a registered dietitian, for individualized guidance.

What is the O positive blood type diet?