Nutrition Theory & Scientific Evidence
What Is the Blood Type A Diet?
The Blood Type A diet is a plant-focused eating pattern popularised by Peter D’Adamo’s blood-type diet theory. The theory proposes that people with blood group A may do better with a largely vegetarian diet and may tolerate some foods differently from people with other ABO blood groups.
These ideas have become popular online, particularly around searches for A positive blood type foods, A negative blood type diets, foods to avoid and Type A meal plans. However, scientific research has not shown that matching a diet to a person’s ABO blood group produces additional health benefits.
This page explains what the Blood Type A diet theory recommends, while clearly separating those recommendations from current scientific evidence and mainstream healthy-eating guidance.
Evidence at a Glance
- A 2013 systematic review found no evidence validating the claimed health benefits of blood-type diets.
- A 2014 study found that greater adherence to the Type A eating pattern was associated with some favourable cardiometabolic markers, but the benefit was unrelated to whether participants actually had blood group A.
- A 2018 analysis likewise found that ABO genotype did not modify the relationship between blood-type diets and cardiometabolic outcomes.
- A 2021 analysis of a plant-based dietary intervention found no meaningful difference in weight, body fat, blood lipids or glycaemic response according to ABO blood type.
In other words, some elements of the Type A pattern may be nutritious, but current evidence does not show that they work specifically because a person has blood group A.
Blood Type A Diet Characteristics
According to the original blood-type diet theory, Type A is described as best suited to a more plant-based, settled agricultural eating pattern. The theory traditionally emphasises:
- a predominantly plant-focused diet;
- plenty of vegetables, fruit, beans, pulses, whole grains, nuts and seeds;
- less red and processed meat;
- moderate use of fish and selected fermented dairy foods;
- an emphasis on minimally processed foods;
- stress management and regular physical activity as part of a wider lifestyle approach.
These are descriptions of the Blood Type Diet theory, not proof that people with group A have a unique digestive physiology or require a different diet from people with other ABO blood groups.
Does the Blood Type A Diet Work?
The strongest available research does not support the idea that people should choose foods according to ABO blood type. A systematic review published in the American Journal of Clinical Nutrition found no studies demonstrating the claimed health benefits of blood-type diets.
A later study of 1,455 adults found that higher adherence to the Type A diet pattern was associated with lower BMI, waist circumference, blood pressure and several metabolic markers. However, the same benefits were seen regardless of whether the person actually had blood group A. The authors concluded that the findings did not support the blood-type diet hypothesis.
This makes nutritional sense: the Type A pattern is rich in vegetables, fruit, beans and other plant foods while limiting red and processed meat. Similar features already appear in evidence-based healthy-eating advice. The potential benefit therefore appears to come from the overall quality of the diet rather than from matching it to blood type.
A Positive vs A Negative Blood Type Diet
People often search separately for an A positive blood type diet or an A negative blood type diet. The positive or negative sign refers to the Rh blood-group system, which is separate from the ABO system used in the original Blood Type Diet theory.
The theory does not provide a scientifically validated reason for people with A+ and A− blood groups to follow different food lists. More importantly, research has not established that either group requires a special diet because of ABO or Rh status.
Blood Type A Food List: What the Theory Recommends
The sections below preserve the main food categories commonly associated with the Type A diet. They should be read as a summary of the theory rather than as medically necessary restrictions.
Meat, Offal and Poultry
The Blood Type A diet traditionally recommends limiting red and processed meat and placing more emphasis on plant proteins. Chicken and turkey are usually treated as more neutral choices within the theory. From an evidence-based perspective, reducing processed meat and choosing more beans, pulses, nuts and other plant proteins can fit a healthy diet, but this advice is not specific to blood group A.
Seafood
The theory allows moderate amounts of selected fish and seafood while labelling some species as less suitable for Type A. There is no established evidence that people with blood group A need to avoid particular fish because of lectins or ABO status. NHS guidance instead recommends a balanced diet that can include fish, including oily fish, according to general dietary needs.
Dairy Products and Eggs
The original Type A diet tends to favour fermented dairy products and plant alternatives while limiting larger amounts of cow’s-milk dairy. Scientific evidence does not show that blood group A itself causes poor dairy digestion. Lactose intolerance, milk allergy and individual preference are separate issues and should be assessed on their own merits.
Oils and Fats
Olive oil is often emphasised in the Type A approach. That choice is compatible with mainstream guidance favouring unsaturated fats, but there is no evidence that people with blood group A uniquely require particular oils or must avoid others solely because of their blood type.
Nuts and Seeds
Nuts and seeds are prominent in the Type A pattern because they provide plant protein, fibre and unsaturated fats. The older theory particularly highlights foods such as peanuts, walnuts, almonds and pumpkin seeds. Claims that individual nuts have special “cancer-fighting” effects for Type A are not established and should not be used as a basis for cancer prevention or treatment.
Beans and Pulses
Beans, lentils and other pulses fit naturally into the plant-focused Type A pattern and are useful sources of protein and fibre. The blood-type diet theory classifies some individual pulses differently, but there is no good evidence that kidney beans or chickpeas impair insulin production specifically in people with blood group A.
Cereals and Grains
The theory generally includes whole grains such as oats, millet, buckwheat and brown rice while advising moderation with wheat. Claims that wheat creates harmful “acidity” in the muscle tissue of people with blood group A are not supported by current evidence. For most people, higher-fibre or wholegrain carbohydrates can form part of a balanced diet unless there is a specific medical reason to avoid them.
Fruit and Vegetables
Fruit and vegetables are central to the Type A diet. The original theory favours many vegetables, berries, plums and pineapple while discouraging selected foods such as tomatoes, peppers, potatoes, bananas and some tropical fruits. There is no established evidence that these foods are broadly unsuitable for people with blood group A. Unless an individual has an allergy, intolerance or another medical reason, variety is generally more important than ABO-based exclusion.
Spices, Herbs and Flavourings
The Type A theory commonly includes foods such as miso, tamari, ginger and selected herbs. These can certainly be part of a varied diet, but they should not be presented as uniquely boosting the immune system of people with blood group A. Likewise, avoiding vinegar or specific spices is not required simply because of ABO blood type.
Beverages
The older diet lists green tea, coffee and occasional red wine among its Type A choices. Blood group A is not a reason to drink alcohol, and alcohol should not be recommended for cardiovascular protection. Water and other low-sugar drinks can support normal hydration, while coffee or tea may be included according to personal tolerance and general health.
Before Cutting Out Foods
Large exclusion diets can make it harder to obtain enough protein, calcium, iron, vitamin B12 and other nutrients. If you have persistent digestive symptoms or think a particular food is causing problems, it is better to discuss this with a GP or registered dietitian rather than excluding multiple foods simply because of blood type.
The NHS also advises caution with some commercially available food-intolerance tests because evidence for accuracy may be limited and unnecessary exclusions can be harmful.
Example Meal Ideas Based on the Type A Diet Theory
The following meals reflect the plant-focused style traditionally associated with the Blood Type A diet. They are examples rather than a personalised medical nutrition plan.
Breakfast
- Oats or muesli with berries, nuts and fortified soya milk
- Buckwheat pancakes with blueberries
- Wholegrain toast with almond butter and fruit
Lunch
- Lentil and vegetable soup with wholegrain bread
- Brown rice, beans and mixed salad
- Soba noodles with vegetables and miso broth
Snack
- Fruit with a small handful of nuts
- Carrot sticks with hummus
- Plain yoghurt or fortified plant yoghurt with berries
Dinner
- Tofu and vegetable stir-fry with brown rice
- Curried lentils with green vegetables
- Grilled trout with root vegetables and salad
A More Evidence-Based Way to Personalise Your Diet
Personalised nutrition can still be useful — just not on the basis of ABO blood type alone. A more practical approach considers your medical history, allergies, diagnosed intolerances, medications, activity level, weight goals, cultural preferences and whether you are meeting your nutritional requirements.
For the general population, the NHS Eatwell Guide recommends a varied pattern with plenty of fruit and vegetables, higher-fibre starchy foods, beans and pulses, appropriate protein foods, dairy or alternatives and mainly unsaturated fats.
Available Separately at Parkland Natural Health
Food intolerance test of 208 ingredients
This is our most comprehensive food and drink test. It analyses your client’s IgG antibody reactions to 208 food and drink ingredients. This test will highlight their food triggers and help you formulate an IgG-guided elimination diet together.
This service is available separately and is not part of the Blood Type Diet theory. Testing should not be used to justify broad food exclusions without appropriate clinical context.
Food allergy test
Do you experience reactions to foods and think an allergy might cause them? Do you experience hay fever-type symptoms, the cause of which is unknown to you? Allergies can be challenging to pinpoint. And it’s almost impossible to deal with an allergy without identifying what is causing the problem. This Food Allergy Test is a fast and reliable home-to-laboratory allergy testing service.
Food allergy testing is a separate clinical question from blood type. Suspected allergy symptoms should be assessed according to appropriate allergy guidance rather than ABO group.
Sources and Further Reading
- American Journal of Clinical Nutrition: Blood type diets lack supporting evidence — a systematic review
- PLOS ONE: ABO Genotype, ‘Blood-Type’ Diet and Cardiometabolic Risk Factors
- Journal of Nutrition: ABO genotype does not modify associations between blood-type diets and cardiometabolic biomarkers
- Journal of the Academy of Nutrition and Dietetics: Blood type is not associated with response to a plant-based dietary intervention
- NHS: The Eatwell Guide
- NHS: Food intolerance
This article discusses the Blood Type Diet as a nutrition theory and summarises current evidence. It is not a substitute for personalised advice from a GP, registered dietitian or other appropriately qualified healthcare professional.
Historical reference: D’Adamo P. Eat Right 4 Your Type. The original blood-type diet concept was popularised in the 1990s.
