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Many people believe that their blood type, whether A, B, AB, or O, is only relevant in relation to blood transfusions. But discussions over recent decades have suggested that eating for a specific blood type may offer some health benefits.

Diets that are based on a person's blood type have been supported by doctors, including the naturopath Peter J. D'Adamo.

However, there is a lack of supporting evidence to validate the proposed health benefits of following a blood type diet.

A review of data published in the American Journal of Clinical Nutrition concluded: "No evidence currently exists to validate the purported health benefits of blood type diets."

Despite the lack of scientific evidence, supporters of blood type diets claim to help people achieve overall good health and a lower disease risk through eating for their specific blood type.

More research is definitely needed, but here, we will learn more about the importance of the body's blood type, and the purported benefits of eating for an A, B, AB, or O blood type.

Fast facts on the A positive (and A negative) blood type diet:

  • Individuals with type A blood may be better suited to natural, vegetarian diets.
  • People with type A blood have been shown to have lower levels of stomach-acid than other blood types, so a meat-based diet may not be digested as easily as a vegetarian based one.
  • Research has suggested that certain blood types may be at risk of developing specific diseases or conditions.
  • People with type A blood also have a higher natural propensity for developing other diseases, such as cancer and diabetes.

Blood has an array of cells that are needed for proper body function. These include plasma, red and white blood cells, and platelets.

Antigens are also present in blood and are responsible for triggering a response by the immune system to counter attacks from foreign substances, such as bacteria and viruses.

One in three people in the United States has A positive blood type, making it the second most common in the country. As such, it can be a good type to have if a person in the U.S. needs a blood transfusion or wishes to donate blood.

People with A positive blood type can receive the following blood types:

  • A positive
  • A negative
  • O positive
  • O negative

A negative is rarer, with 1 in 16 people having the blood group, and able to receive only A negative and O negative transfusions.

The common blood types vary in different countries, so if you are outside the U.S. and need a blood transfusion be sure to check for the common types in your area.

Be sure to make the necessary arrangements if you are in a part of the world with fewer A positive donors, such as Asia, as it may be harder to receive the treatment you need.

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Different blood types are believed to have different reactions to certain foods. The blood type A diet is designed to provide the most benefits to those with blood type A.

D'Adamo argues that when the blood comes in contact with certain food components, a chemical reaction occurs, specifically with proteins called lectin.

Lectins, which are proteins found in food, have believed to have a direct effect on the blood and the digestive tract.

These proteins bind to cells within the body, causing them to clump together and potentially cause hormonal disruptions. This disruption has a similar effect on the body as a foreign substance might.

Certain foods are recommended for people with type A blood to eat, as well as avoid, in order to maintain optimal health. According to the diet, these are the foods that those with blood type A may benefit from:

Animal proteins

Although people with type A blood may be best suited to a vegetarian diet, some animal products are allowed, including:

According to the diet, people with type A blood may consume most kinds of seafood with the most beneficial being:

  • carp
  • cod
  • grouper
  • mackerel
  • monkfish
  • pickerel
  • red snapper
  • rainbow trout
  • salmon
  • sardine
  • sea trout
  • silver or yellow perch
  • snail
  • whitefish

Exceptions are on the "avoid list" of animal proteins further down this article.

Dairy

Digesting dairy is allegedly difficult for people with type A blood, but certain types of dairy may be acceptable, including:

  • yogurt
  • kefir
  • cheeses, including mozzarella, feta, goat cheese, ricotta, and string
  • cheese
  • goat milk

Nuts and fats

Nuts are a great source of protein and healthful fats. People following the type A blood diet can typically have most nuts, except for the ones listed in the "avoid" list. The most beneficial nuts for people following the diet include:

The most beneficial fats for people following the diet to eat include flaxseed oil and olive oil. Other allowable fats include canola and cod liver oil.

There is a selection of peanuts, pumpkin seeds, and walnuts available for purchase online.

Beans

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Beans are an excellent source of protein, iron, and fiber, and most types are acceptable in a blood type A diet.

According to the diet, beans are well-tolerated by people with type A blood, and those considered to be most beneficial include:

  • adzuki beans
  • back and green beans
  • pinto beans
  • red soy
  • black-eyed peas
  • lentils

Grains

While most grains are well-tolerated by people with type A blood according to the diet, the most beneficial may include:

  • amaranth
  • buckwheat

There is a selection of amaranth and buckwheat available for purchase online.

Allowable breads and grains include:

  • essene, Ezekiel, soya flour, and sprouted wheat
  • rice cakes
  • oat, rice, and rye flour
  • soba noodles
  • artichoke pasta

Vegetables

Many vegetables may be well-suited to people following the diet. Some of the recommended ones include:

  • garlic
  • onions
  • broccoli
  • carrots
  • collard greens
  • kale
  • pumpkin
  • spinach
  • artichoke
  • chicory
  • greens, such as dandelion and Swiss chard
  • horseradish
  • leek
  • romaine
  • okra
  • parsley
  • alfalfa sprouts
  • tempeh
  • tofu
  • turnip

The exceptions to the vegetable rule are listed below.

Fruits

Similarly to vegetables, type A blood group individuals may be well-suited to fruits. Some of the recommended fruits for people following the diet include more alkaline fruits, such as:

  • plums
  • prunes
  • figs
  • grapefruit
  • lemon
  • pineapples
  • cherries
  • apricots
  • most berries, including blackberries, blueberries, boysenberries, and cranberries

Exceptions to the fruit rule are listed further down this article.

Spices and condiments

Spices and condiments that people following the diet are alleged to benefit from include:

  • tamari
  • miso
  • soy sauce
  • garlic
  • ginger
  • blackstrap molasses

There is a selection of tamari, miso, soy sauce, garlic, ginger and blackstrap molasses available for purchase online.

Beverages

Beverages that the diet allows include:

Listed here are some of the foods that type A blood group individuals are advised to avoid for optimum health, according to the type A diet.

Animal proteins

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Shellfish, including shrimp, mussel, scallop, and oyster, are avoided by the blood type A diet.

The diet for A blood types recommends people to avoid consuming most animal meat products and certain seafoods, such as:

  • beef
  • pork
  • lamb
  • veal
  • venison
  • duck and goose
  • anchovy
  • barracuda
  • beluga
  • bluefish
  • bluegill bass
  • catfish
  • caviar
  • clam
  • conch
  • crab
  • crayfish
  • eel
  • flounder
  • frog
  • gray sole
  • haddock
  • hake
  • halibut
  • herring
  • lobster
  • lox
  • mussels
  • octopus
  • oysters
  • scallop
  • shad
  • shrimp
  • squid
  • striped bass
  • tilefish
  • turtle

Dairy

The diet suggests that people should avoid dairy products, including all cheeses and milk not listed in the allowed list.

Nuts and fats

Certain nuts and fats should be avoided by people following the diet, including:

  • Brazil nuts
  • cashews
  • pistachios
  • corn, cottonseed, peanut, safflower, and sesame oils

Beans

Although beans are typically well-tolerated according to the diet, there are some that should be avoided, including:

  • garbanzo
  • kidney
  • lima
  • navy
  • red
  • tamarind

Grains

While most grains may be well-tolerated by people with type A blood, the diet suggests that some should be avoided, including:

  • cream of wheat
  • farina
  • granola
  • grape nuts
  • wheat germ
  • shredded wheat
  • wheat bran
  • durum wheat

Breads that the diet avoids include:

  • English muffins
  • breads, such as high-protein whole wheat and multi-grain breads
  • matzos
  • pumpernickel
  • wheat bran muffins
  • white and wholewheat flour
  • pastas, including semolina and spinach

Vegetables

Although many vegetables are well-tolerated by people with type A blood according to the diet, it recommends that these should be avoided:

  • peppers
  • olives
  • potatoes
  • sweet potatoes
  • yams
  • cabbages
  • tomatoes
  • lima beans
  • eggplant
  • mushrooms

Fruits

According to the diet, people with type A blood typically tolerate most fruits very well, with potential exceptions being:

  • melons, such as cantaloupe and honeydew
  • oranges
  • tangerines
  • strawberries
  • rhubarb
  • mango
  • papaya
  • bananas
  • coconut

Spices and condiments

Spices and condiments to be avoided include:

  • vinegar
  • peppers, including black, cayenne, and white
  • capers
  • plain gelatin
  • wintergreen
  • ketchup
  • mayonnaise
  • pickles
  • relish
  • Worcestershire sauce

Beverages

Beverages the diet avoids include:

  • beer
  • black tea
  • distilled liquor
  • seltzer water
  • soda

While the blood type diet has gained popularity in recent years, it is important to bear in mind that there is a lack of evidence supporting its claimed benefits.

The diet can be restrictive and could get expensive, and it may be extremely time consuming to prepare meals from the provided food lists.

There has not been rigorous scientific study on the blood-type diet, as stated by D'Adamo himself, aside from a 2014 PLoS ONE study that concluded, "the findings do not support the blood-type diet hypothesis."

As with any diet or exercise program, it is important to speak with a doctor before starting a diet for blood type.