If you buy something through a link on this page, we may earn a small commission. How this works. Many people only see a person’s blood type as important when it comes to giving blood or receiving a blood transfusion. However, some argue that eating a diet specific to a particular blood type may offer health benefits. A naturopath called Peter D’Adamo popularized the idea that a diet based on blood type could help a person achieve good overall health and reduce the risk of developing certain diseases. However, research on the effects of a blood type diet is scarce, and the studies available have not proven its effectiveness. For example, the authors of a 2014 study concluded that their findings did not support the claims that a blood type diet provides specific benefits. A 2013 review of data relating to the blood type diet also found that no evidence is currently available to verify the benefits of this eating plan. In this article, we explain why some people believe that their blood type should influence their diet. We also look in more detail at the proposed benefits of eating for the O positive and negative blood types and discuss which foods a person following this diet should eat and avoid.

Eating for your blood type Share on Pinterest A person on a O blood type diet can eat most types of vegetables. Different blood types may make people more or less susceptible to certain conditions. A large genetic study from 2019, for example, found that people with type A and AB blood have an increased risk of gastric cancer. The results of an earlier study suggested that people belonging to the A, B, or AB blood groups have an increased risk of coronary heart disease. A 2019 study in Croatia also found an association between the AB blood type and the risk of psychiatric disorders. The researchers suggested that those in the AB blood group are three times as likely as those in other blood groups to have a psychiatric disorder. According to D’Adamo, a chemical reaction occurs when the blood comes into contact with certain foods, specifically with a protein called lectin. Lectins have a direct effect on the blood and the digestive tract. The protein binds to cells within the body, causing them to clump together, which can potentially lead to hormonal disruptions. The effect that this produces on the body is similar to that of a foreign substance being present. D’Adamo suggests that people with different blood types react differently to particular types of food and their lectins. As a result, he recommends specific diets for people with these different blood types. However, no research to date suggests that lectins affect people in specific blood groups differently. A 2014 study showed that adhering to the blood type O diet reduced levels of triglycerides in the blood, the storage form of fat. Despite this, the study authors concluded that the drop in triglyceride levels occurred due to factors unrelated to a person’s blood group. Read more about the lectin-free diet here.

Foods to eat According to proponents of the diet, people with blood type O should eat and avoid certain foods. It is worth noting again that there is little reliable evidence to support the use of this diet. Animal proteins The diet plan dictates that people in the O blood group should consume “beneficial” animal products, including: beef

lamb

mutton

veal

venison

cod

herring

mackerel People with type O blood following the diet are allowed to consume most meat products, including cold-water fish. Dairy Although people looking to follow the blood type O diet should generally avoid dairy and eggs, they can occasionally consume the following products: butter

cheeses, such as farmer, feta, mozzarella, and goat’s cheese

soy milk Nuts Nuts are a great source of protein and healthful fats, and people following the diet can typically have most nuts, except for the ones in the “foods to avoid” list below. Suitable nuts and seeds, including walnuts, hazelnuts, and almonds, are available to purchase online. Pumpkin seeds and walnuts supposedly provide the most benefits. Beans People with type O blood tolerate beans. Proponents of the diet believe that the most beneficial beans for these individuals are: adzuki beans

pinto beans

black eyed peas Grains While most people on the O positive and negative diet should avoid grains, a few can remain in the diet, including: amaranth

buckwheat

rice

kamut

kasha

millet Some people may also be able to eat gluten-containing grains, while others will be unable to tolerate them. These grains include: barley

rye

spelt

Essene bread and Ezekiel bread Many of the less widely available grains are available to purchase online, including amaranth, kamut, and kasha, as well as Ezekiel bread. Vegetables With a few exceptions — which are on the list of foods to avoid — people with type O blood can eat most vegetables, including: tomatoes

artichoke

chicory

dandelion

garlic

horseradish

kale

okra

onions

parsley

parsnips

red peppers

sweet potatoes

pumpkin

seaweed

turnips Fruits Some of the recommended fruits for people with type O blood include: plums

prunes

figs

grapefruit

most berries Spices and condiments Spices that people following the diet can enjoy include: kelp-based seasoning

iodized salt

parsley

curry

cayenne pepper

chocolate

cocoa

honey People can purchase many of these ingredients online, including kelp-based seasoning and iodized salt. Beverages People following an O positive and negative diet can drink the following: seltzer water

club soda

sparkling water

tea

wine

Foods to avoid Supporters of the diet suggest that people with type O blood may experience unwanted weight gain when they eat particular food groups, such as dairy. Specific products, such as wheat-based foods that contain gluten, may also lead to an inflammatory and autoimmune response. Animal proteins The diet plan for people with type O blood excludes: pork, including ham and bacon goose

barracuda

pickled herring

catfish

smoked salmon

caviar

octopus

conch Dairy People following the diet should avoid dairy products not in the “foods to eat” list, including yogurt. Nuts Particular nuts also do not feature in the diet plan, including: Brazil nuts

cashews

peanuts

pistachios

poppy seeds Beans Beans that proponents of the diet advise against include: copper beans

kidney beans

tamarind beans

lentils, including domestic, green, and red lentils Grains The diet also excludes the following grains: corn

gluten

graham

bulgur, durum, sprouted, white and whole wheat

wheat germ and bran

farina

oat

seven grain Vegetables Although people in blood group O tolerate many vegetables well, the advice is that they should avoid: vegetables belonging to the Brassica family, including cabbage, Brussels sprouts, cauliflower, and mustard greens alfalfa sprouts

shiitake mushrooms

fermented olives

vegetables from the nightshade family, including eggplant and potatoes

corn

leek Fruits People following the O positive and negative diet should also avoid several specific fruits: melons, including cantaloupe and honeydew

oranges

tangerines

strawberries and blackberries

rhubarb

avocado

coconut and products that contain coconut Spices and condiments Spices and condiments to avoid in the diet include:

pepper, both white and black

vinegar

capers

cinnamon

cornstarch and corn syrup

nutmeg

vanilla

ketchup

pickles

mayonnaise

relish Beverages People with type O blood should avoid drinking the following, according to the diet plan: beer

coffee

distilled liquor

black tea

What is the O blood type? Blood consists of many vital components, including plasma, red and white blood cells, and platelets. The blood also contains antigens. These are substances on the surface of the cell that trigger the immune system to attack foreign compounds and organisms, such as bacteria. Antigens can also trigger the immune system to attack blood types that have different antigens. Doctors classify blood types as A, B, AB, and O. They also label them as either rhesus (Rh) positive or Rh negative to denote the presence or absence of an antigen called Rh factor. For example, a person with O+ blood does not have A or B antigens on the surface of the cells but does have Rh factor. In contrast, O- blood has no A or B antigens and no Rh factor. For this reason, medical experts consider type O- blood to be a universal red cell donor type.