Diets that do and diets that don’t: Part 3 – The Blood Group Diet

By Tamzyn Murphy

BSc Med(Hons) Human Nutrition and Dietetics, RD


Eat right for your type, by naturopathic doctor Peter D’Adamo, was first published almost 20 years ago, but it’s more popular than ever. It advises people to eat certain foods and avoid others based on their blood type – O, A, B or AB. According to D’Adamo, your blood type determines how your body digests lectins (anti-nutrient proteins found in certain foods). Apparently, eating lectins that are incompatible with your blood type causes a host of adverse health effects, from bloating and inflammation to weight gain. Allegedly, your blood type even determines what exercise suits you best.


Foods are categorised as ‘highly beneficial’ (with medicinal effects), ‘neutral’ (acting as a food) or ‘avoid’ (toxic) for each blood type. O (“for old” – humanity’s oldest blood line) types are told to follow a meat-based diet and vigorous exercise programme.  Type A (for “agrarian”) should eat vegetarian food and exercise gently. B types are thought to have nomadic genes and digestive systems that can tolerate many foods, except, amongst other things, wheat, corn and lentils. Bs should exercise moderately. D’Adamo says the “modern” AB blood type has a sensitive digestive tract and should avoid meat and poultry but can enjoy seafood, tofu, dairy, and most fresh produce. ABs should do calming exercises.


People probably love this diet because it sounds scientific; but nothing could be further from the truth. There is absolutely no evidence that some foods or exercises are good for people of one blood type and “dangerous” for another. It appears that D’Adamo has randomly bestowed fictional characteristics upon people of different blood types and thumb-sucked foods to put on his ‘beneficial’ and ‘avoid’ lists. If the diet has worked for you it’s probably because all blood types are encouraged to eat real, whole and natural foods in place of processed, sugary and fatty choices, and exercise is always recommended. These are prudent health recommendations that’ll work for anybody. Also each of the four diets loosely resembles a diet that has been shown to have weight loss benefits: The O diet’s a variation on the typical high protein, low carb diet; A’s vegetarian; B’s somewhat similar to the Mediterranean and low GI/GL diets and AB is Pescatarian. In my opinion, the blood type diet’s a perfect example of a fad diet that profits from people’s desperation. If it works, it’s not for the reasons you think.



[i] WebMD. The eat right for your blood type diet. Sep 2013

[ii] Eat right for your type. Sep 2013