The Blood Type Diet: Eating Right for Your Blood Type O, A, B, AB

Have you ever followed a diet perfectly — at least on paper — and yet it just didn't seem to work for you? While your friend on the exact same plan shed kilograms easily? The Blood Type Diet, first popularised by Dr. Peter D'Adamo in his 1996 book Eat Right 4 Your Type, offers an intriguing answer: maybe the "right" diet is different for every person, and your blood type could be a key to understanding what your body needs.

Over two million copies of D'Adamo's book have been sold worldwide, and there are passionate communities of people who swear the Blood Type Diet transformed their health. But there are also scientists who point out the lack of robust clinical evidence. As always, the truth is nuanced — and in this guide, we'll give you an honest, balanced look at the theory, the evidence, and how South Africans can practically explore this approach.

What Is the Blood Type Diet Theory?

Dr. D'Adamo's central theory is that your ABO blood type reflects your ancient ancestry and digestive evolution. Different blood types appeared at different points in human history, he argues, and each is therefore adapted to different foods:

• Type O — The oldest blood type, linked to ancient hunter-gatherer ancestors. Best suited to animal proteins, struggles with grains and dairy.
• Type A — Appeared with the rise of agriculture. Better suited to plant foods and struggles with heavy meat consumption.
• Type B — Associated with nomadic peoples. A balanced omnivore type that can handle a variety of foods but may react poorly to chicken and corn.
• Type AB — The most recent blood type, a blend of A and B characteristics. A mixed diet suits this type, but smoked and cured meats may be problematic.

D'Adamo also introduced the concept of "lectins" — proteins found in many foods that, he claims, react differently with different blood type antigens, causing agglutination (clumping) of blood cells in incompatible combinations. This, he argues, is the mechanism behind why certain foods are "wrong" for certain blood types.

Blood Type O: The Hunter's Diet

What Type O Should Eat

• Lean red meat (lamb, beef, venison)
• Poultry (except chicken according to some interpretations)
• Fatty fish (salmon, mackerel, sardines)
• Most vegetables (especially leafy greens and broccoli)
• Fruit (especially figs, plums, and berries)
• Olive oil and flaxseed oil
• Walnuts and pumpkin seeds

What Type O Should Limit or Avoid

• Wheat and wheat products (a big one — D'Adamo claims wheat lectin is particularly problematic for Type O)
• Most grains (corn, barley to a lesser extent)
• Dairy products
• Beans and lentils
• Potatoes

SA-Friendly Type O Foods

South Africa is excellent for Type O eaters. Free-range lamb, local game meats (springbok, kudu), snoek and pilchards, abundant fresh vegetables, and local fruits like guavas, pawpaw, and plums are all on the beneficial list. The Type O diet has strong overlap with the popular Banting Diet — both emphasise animal proteins and limit grains. Many South African followers of Banting may find Type O guidelines feel intuitively right.

Blood Type A: The Cultivator's Diet

What Type A Should Eat

• Vegetables (all types, especially dark leafy greens)
• Fruits (most are fine, particularly berries and apples)
• Legumes (lentils, black beans, soy)
• Whole grains (rice, oats, rye)
• Fish (especially salmon, sardines, and cod)
• Nuts and seeds (especially peanuts, pumpkin seeds, sunflower seeds)
• Olive oil and flaxseed oil

What Type A Should Limit or Avoid

• Red meat — D'Adamo suggests Type A is best suited to a primarily plant-based diet
• Dairy products (especially full-fat dairy)
• Kidney beans
• Wheat (in large amounts)

SA-Friendly Type A Foods

The Type A diet is very accessible in South Africa. Red lentils at R30–R40 per bag, canned and dried chickpeas, abundant fresh vegetables from any market, and affordable oats for breakfast make this an easy and budget-friendly way to eat. Type A guidance overlaps significantly with vegetarian and plant-forward diets.

Blood Type B: The Nomad's Diet

What Type B Should Eat

• Lamb, mutton, and venison
• Fish (most types)
• Dairy products (Type B is the most "dairy-friendly" blood type according to D'Adamo)
• Eggs
• Green vegetables
• Most fruits
• Rice (over wheat)
• Oats, millet, and spelt

What Type B Should Limit or Avoid

• Chicken — D'Adamo specifically flags chicken as problematic for Type B, citing a lectin in chicken muscle tissue
• Corn
• Wheat
• Lentils
• Peanuts
• Sesame seeds

SA-Friendly Type B Foods

South Africa is extremely well-suited for Type B eating. Lamb is a staple in many South African households (particularly in the Cape and among Afrikaner and Muslim communities), full-cream milk and cheese are widely consumed, and eggs are affordable and universally available (typically R30–R60 per dozen). The instruction to avoid chicken is the most unusual element — something many South Africans would find challenging given how central braai chicken is to local culture!

Blood Type AB: The Enigma Diet

What Type AB Should Eat

• Tofu and other soy products
• Seafood (especially tuna, salmon, sardines, and cod)
• Dairy (in moderate amounts, as tolerated)
• Most vegetables
• Legumes (especially lentils, peanuts)
• Most fruits (except some citrus and tropical fruits)
• Whole grains

What Type AB Should Limit or Avoid

• Smoked and cured meats (bacon, salami, smoked sausage)
• Alcohol (beyond very moderate amounts)
• Corn
• Buckwheat
• Red meat in large quantities

SA-Friendly Type AB Foods

AB types in South Africa have a broad range of foods to choose from. Tinned tuna and pilchards are affordable and convenient; tofu is increasingly available at Pick n Pay and Checkers for around R30–R50 per block; and the South African variety of fresh vegetables is enormous. The main lifestyle shift for many South Africans would be reducing processed and cured meats — boerewors, bacon, and polony — which are all flagged as problematic for Type AB.

The Scientific Controversy: What the Research Actually Shows

Here's where we need to be honest with you: the scientific evidence specifically supporting the Blood Type Diet's core claims is, at present, weak. A large 2013 systematic review published in the American Journal of Clinical Nutrition found no evidence that the proposed blood type diets produce the health effects claimed, and noted that "no studies that showed benefits of blood type diets were found."

A 2014 study from the University of Toronto involving over 1,400 participants found that while the Type A diet (plant-based) and Type O diet (meat-heavy, grain-free) did produce positive health markers — those benefits appeared equally in people regardless of their actual blood type. In other words, the diets might work, but not because of blood type.

However, there are important nuances worth acknowledging:

• The research on blood type diets is still relatively limited. Absence of strong evidence is not the same as evidence of absence.
• Many people who follow Blood Type Diet guidelines report feeling dramatically better — improved energy, digestion, and weight loss. These subjective experiences are real, even if the mechanism may not be what D'Adamo proposed.
• Each of the four blood type diets eliminates processed foods, encourages whole foods, and reduces sugar. This alone could explain much of the reported benefit — regardless of blood type.
• Nutritional science is still evolving. Personalised nutrition based on genetic and biological markers is an active research field, and future evidence may shed more light on individual variation in dietary response.

A Balanced Take for South Africans

The honest advice here is this: if you're curious about the Blood Type Diet, trying it for 30 days is unlikely to harm you — each blood type's food list is built around whole, nutritious foods with minimal processed food. Many people report genuine improvement in how they feel. Whether that's due to blood type-specific mechanisms or simply eating better quality food is unclear.

What we do know is that no diet works perfectly for everyone, and paying attention to how specific foods make you feel — your energy, digestion, hunger levels, and mood — is genuinely valuable personalised nutrition, whatever the theoretical basis.

If you're looking for approaches with stronger scientific consensus, explore our guides on intermittent fasting, the Banting Diet Plan, or the latest medical weight loss options in our GLP-1 Weight Loss Guide. Our Diet Plans comparison page is a great place to start if you're not sure which approach fits your life.

Finding Your Blood Type in South Africa

Not sure of your blood type? You can find out through your GP, most private hospitals, or blood donation centres like the South African National Blood Service (SANBS). Blood type testing is typically done as part of routine blood work, or you can request a specific blood typing test — usually at minimal cost through medical aid or for under R100 privately.

The Bottom Line

The Blood Type Diet is a fascinating concept that has helped many people make better food choices — even if the science behind why it works remains debated. The food lists for each type are generally healthful and whole-food focused. The biggest risk is not the diet itself but treating it as an absolute truth rather than a useful framework to explore with an open mind and your doctor's support.

Eat well. Pay attention to how your body responds. Work with a healthcare professional. And remember — the best diet is the one you can actually stick to, that makes you feel good, and that you enjoy. Check your metrics with our BMI Calculator and explore our Nutrition Guide for broader evidence-based eating advice.