Some people believe that eating for their specific blood type may offer health benefits. However, there is little evidence to suggest that they work.
Diets based on a person’s blood type have been supported by some health influencers and naturopaths. However, there is a lack of scientific evidence to support them.
Here, we will learn more about the importance of the body’s blood type and the purported benefits of eating for an A positive or negative blood type.
Blood contains multiple components, each with a different function. These include plasma, red blood cells (RBCs), white blood cells, and platelets.
In the RBCs, there are antigens, while in the plasma, there are antibodies. These substances trigger an immune response when a pathogen, or germ, enters the body.
However, there are two different types of antigen: A and B. The presence or absence of these antigens determines a person’s blood type, as well as to whom they can safely donate blood or receive it.
People with type A blood have A antigens in their RBCs and B antibodies in their plasma. Whether they are A positive or A negative depends on another substance, known as the Rh factor.
If the Rh factor is present, a person has A positive blood. If the Rh factor is not present, they have A negative.
The concept of the blood type diet originated from a 1996 book by naturopath Dr. Peter J. D’Adamo. In the book, he argues that individuals with different blood types require different diets to optimize their health.
Much of the theory behind this revolves around proteins known as lectins. Lectins are naturally present in food and act as “glue”, binding to carbohydrates.
Proponents of the blood type diet claim that if a person eats lectins that are not compatible with their blood type antigens, they can begin clumping together and cause harm.
A 2023 review of past research found little evidence to support the benefits of blood type diets. The authors conclude that the data on them is “limited and controversial”.
However, individuals with different blood types may have varying risks of developing certain conditions. For example, people with type A blood have a higher risk of cardiovascular disease (CVD) than those with type O.
Those with a higher risk of CVD for any reason could benefit from dietary changes to reduce their risk, such as adopting a mostly plant-based diet. The blood type diet recommends this for those with type A blood.
However, a 2021 study found that blood type did not influence responses to this dietary change. After 16 weeks, there were very similar changes in weight, body fat, blood sugar regulation, and plasma lipid concentrations in people with type A and type O blood.
The study did not specifically use the blood type diet, but it does suggest that a plant-based diet has similar effects on most people.
Proponents of the blood type diet say that individuals with type A blood should follow a predominantly plant-based diet, with limited or no consumption of meat and processed foods.
The diet categorizes foods into “beneficial”, “neutral”, and “avoid” groups, based on how healthful they are meant to be for people with type A blood:
| Beneficial | Neutral | Avoid | |
|---|---|---|---|
| Meat | chicken turkey | red meat | |
| Fish and seafood | cod salmon sardine trout snail | bass tuna tilapia swordfish shark | crab lobster crayfish catfish shrimp oyster octopus |
| Dairy | soy milk | eggs certain cheeses yogurt | American cheese cheddar cottage cheese cream cheese ice cream cow’s milk butter |
| Grains | oats oat flour products soba noodles | rice corn muffin spelt bread gluten-free bread | whole wheat bread English muffin |
| Nuts and fats | peanuts pumpkin seeds flaxseeds and flaxseed oil olive oil | almonds pecans sesame seeds sunflower seeds | cashews pistachio |
| Vegetables | collard greens beet greens spinach garlic onion broccoli carrot pumpkin turnip | zucchini cucumber iceberg lettuce asparagus beets corn Brussel’s sprouts squash cauliflower | potatoes cabbage eggplant black olives peppers tomato |
| Fruits | cherry cranberry plum or prune grapefruit lemon pineapple | apple avocado kiwi grape peach pear strawberry raspberry pomegranate watermelon | banana coconut papaya mango honeydew melon orange tangerine |
It is important to note that this diet plan has no evidence showing it is more beneficial than other plant-based or heart-healthy diets.
Eating a diet that focuses generally on vegetables, grains, lean proteins, and healthy fats can be beneficial.
However, the blood type diet is more specific and limited than other plant-based or pescatarian diets, and may have some potential disadvantages.
Unnecessary restriction
The blood type A diet advises people to avoid specific fruits, vegetables, and types of seafood based on a theory that has not been substantiated in scientific research.
This could mean that people who follow this diet impose unnecessary restrictions on themselves. This may make it more difficult to shop for groceries, find suitable recipes, travel, or eat out with others.
High-mercury fish
Some of the foods in the “neutral” category of the blood type A diet, such as shark and swordfish, contain high amounts of mercury, which is a toxic substance.
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Worsened disordered eating
The desire to follow a limited or strict eating pattern can have links with orthorexia, a type of disordered eating that occurs due to a preoccupation with one’s health.
For example, a 2019 review of past research found evidence that people following a vegetarian diet were more likely to have orthorexia-like behaviors. A 2022 prospective study also found a link between these diets and orthorexia, as well as the number of different diets people followed.
Any strict eating plan could potentially reinforce or exacerbate these tendencies.
If a person finds they are increasingly worried about the food they eat being “clean” or “pure”, they should reach out to a doctor or mental health professional for support.
Help is available
Eating disorders can severely affect the quality of life of people living with these conditions and those close to them. Early intervention and treatment greatly improve the likelihood of recovery.
Anyone who suspects they or a loved one may have an eating disorder can contact the National Alliance for Eating Disorders, which offers a daytime helpline staffed by licensed therapists and an online search tool for treatment options.
For general mental health support at any time, people can call the Substance Abuse and Mental Health Services Administration 24 hours a day at 1-800-662-4357 (or 1-800-487-4889 for TTY).
Many other resources are also available, including:
- The National Association of Anorexia Nervosa and Associated Disorders
- F.E.A.S.T., which provides support and educational resources to friends and family who want to help someone living with an eating disorder
While the blood type diet has gained popularity in recent years, it is essential to note that there is a lack of evidence supporting its claimed benefits.
Additionally, the diet can be restrictive, and it may be time consuming or inconvenient to prepare meals from the provided food lists.
As with any diet or exercise program, it is essential to consult a doctor before beginning. There may be more well-researched ways to achieve a person’s health goals.