Blood type diet
The idea that you should eat for your blood type is popular. The research says the diets help, when they do, for reasons that have nothing to do with blood type.
The claim
Peter D’Adamo’s 1996 book Eat Right 4 Your Type argued that proteins in food called lectins react differently with each ABO group, so each type should eat differently:
- Type O: high-protein, meat-heavy, low in grains.
- Type A: mostly vegetarian, low in red meat.
- Type B: varied, dairy allowed, avoiding chicken and corn.
- Type AB: a mix of A and B, with seafood, tofu and dairy.
What studies found
A 2013 systematic review in the American Journal of Clinical Nutrition looked at more than 1,400 papers and found no study that tested the blood type diet properly and showed a benefit.
A 2014 University of Toronto study in PLOS ONE put 1,455 people’s eating patterns against the four diets. Some diets did improve markers like blood pressure and cholesterol, but the benefit was the same whatever the person’s blood type. In other words: it was the healthier food, not the match.
The type A diet looks good in studies for the same reason any mostly-plant diet does. If you’re considering a big change, talk it through with a doctor or registered dietitian.
Blood type personality
In Japan and South Korea, ketsueki-gata (blood-type personality) is a staple of magazines and dating apps: type A is said to be careful, B free-spirited, O confident and AB eccentric. It dates to a 1927 paper by Takeji Furukawa that did not hold up.
A 2015 study by Kengo Nawata analysing more than 10,000 people in Japan and the US found that blood type explained less than 0.3% of the variation in personality answers: effectively nothing. What blood type does tell you is who you can give blood to. See the blood type compatibility chart.
Frequently asked questions
Does the blood type diet work?
There is no good evidence that eating for your blood type improves health. A 2013 systematic review in the American Journal of Clinical Nutrition found no studies supporting it, and a 2014 study in PLOS ONE found that where the diets helped, they helped people regardless of their blood type.
What is the blood type diet?
A plan popularised by naturopath Peter D’Adamo in the 1996 book Eat Right 4 Your Type. It assigns foods by ABO group, for example high-protein meat-based eating for type O and a mostly vegetarian diet for type A.
Is there a link between blood type and personality?
The idea (ketsueki-gata) is popular in Japan and South Korea, but large studies, including a 2015 analysis of over 10,000 people in Japan and the US, found no meaningful link between blood type and personality traits.
Does blood type affect health at all?
A little, in specific ways. Type O is linked to slightly lower risk of blood clots and heart disease but higher risk of peptic ulcers; non-O types have higher von Willebrand factor levels. These are small population-level effects, not reasons to change your diet.