My blood is type 0, negative rH and they told me I am supposed to stuff my face with steaks, but I should not eat duck and I must forget about amatriciana entirely. Hello everyone, welcome back on the channel of your friendly neighbourhood chemist. Today we breach a topic many of you asked about: blood type diets. To make this a generally interesting video, we’re going to use this example to illustrate how to delve into a given topic in the scientific literature, how to look for scientific articles. As you will know, our blood can be classified in types There are a few classifications, the most popular of which being the one dividing into A, B 0 or AB. Without going into too many details, blood type is identified by looking at which molecules bind to a specific protein found on the surface of red blood cells. In simple terms, type A means there is a specific molecule – a sugar – bound to the protein on the red blood cell’s surface, type B means there is a different molecule, type AB means both are there, and type 0 means none of the two are there. Knowing your blood type is important in several situations, such as when receiving a blood transfusion or to see whether a fetus’ blood is compatible with the mother’s. The first person that succeeded in associating a diet, a way of eating, to blood type was Peter d’Adamo in the US – note that he is not a doctor, nor a dietitian, nor a professional; he is a naturopath, a title not recognized by the scientific community. In 1996 he publishes his book “Eat right for your type”, so eat the right food for your blood type it becomes a global bestseller, selling over 7 millions copies, translated in over 60 countries in Italy this diet has been, changed, popularized by another book by the now-famous doctor Mozzi who has a huge following during public events – I saw them. It was published in 2012 and remains a bestseller, if you look on Amazon it has been in the top selling lists for years. According to d’Adamo, your blood type has a sort of genetic memory, an imprint of what our ancestors used to eat when we first saw that blood type, and according to d’Adamo’s narrative, which is followed by others, the ancestral type, the most ancient one, is type 0 and since our ancestors were mostly hunters and gatherers, therefore type 0 is the hunter, and to be healthy they should eat what hunters used to eat, so meat, and I am type 0, so my favourite food should be meat. Agriculture was not invented yet so no spaghetti. Continuing with this narrative type A appeared much later, more or less at the time where agriculture was developing, and therefore type A is the farmer that should eat mostly vegetables, and less meat. Type B – again following this line of thinking – is the nomadic group, since it supposedly appeared among nomadic tribes that lived off milk, fermented milk, diary products and so this should be the preferred food category for a type B. Type AB is a mix between type A and type B. There are other details, such as looking at some molecules called lectins but they are quite irrelevant after all, but is it really true that type 0 is the oldest one? Well, not exactly: I asked my friend a geneticist and great writer, Guido Barbujani he wrote a few books, one of my favourites is “Noi siamo gli africani” [no English translation], when I told him this story he replied: “well, no, actually this is not true”, and he was surprised to see this story around, so he sent me a few scientific publications, he sent me an article that tells the evolutionary story of blood types, let me summarize it. The genes regulating type A or B are found in many vertebrates they are not found in fish, but are found for instance in frogs; so from an evolutionary standpoint it looks like blood types appeared after the evolutionary lines of fish and amphibians separated. We find type A and B in many animals: dogs, rats, horses, pandas, frogs, rabbits, bats and many others. Type 0 appeared later as a mutation in the genes – for the nitpickers, alleles – that decided between type A and B, so to be precise type 0 is the last one in order of apparition, not the first, and anyway when the Homo genus appeared all of them existed already. It is not true that our hunter ancestor always had type 0 and that type A appeared together with the development of agriculture, not at all: it looks like type A was the first, then type B, and then type 0 after a mutation, so we can throw away the narrative that type 0 is the hunter while type A is the farmer it has no scientific basis, but even if there was, assuming blood types really appeared as told in this story, this is still meaningless: there is no reason to associate diet during a historical period to mutations related to a new blood type. Let’s make a simple example: tomorrow we have a new genetic mutation that creates a new blood type, let’s say type Z. What should we think, that type Z is genetically predisposed to eating fastfood, fried chicken, fries and hamburgers? No! You see that this makes no sense, but maybe, even if this theory is based on nothing, for some unknown reason maybe the diet makes sense: in science, the absence of an explanation for a phenomenon can never be used to say “Ah, this makes no sense”, first we verify if the phenomenon exists and then maybe we look for the explanation: there are many phenomena in our universe that are still waiting for the explanation. So let’s ask the first question. Is this theory clearly wrong? Is there some reason it is pointless to even take it into consideration? There are pseudo-theories that make no sense, for which there is no reason of investigating: think about astrology. Here we can ask a preliminary question: “Is it absolutely nonsensical to have a correlation even a weak one, between blood type and our health, thus indirectly with what we eat?” To answer this question we go look for articles: those working in universities, or research centers or in some companies have access to specialized databases, but at home you can use, I do it very often as I find it convenient for a first search, Google Scholar: the Google service for scientific articles. What do I look for? Well, when starting a new research on a topic what I find useful is to start from what is called a “systematic review”. These are articles where somebody worked to read all the scientific publications on a given topic read and verify them, discarding those that they thought lacked support, compared those contradicting each other, sorted them by time and at the end the article is a review of what the entire scientific community – not just scientist X – thinks about the topic. Let’s see what happens if we look e.g. for a possible correlation between cancer and blood type, so we search on Google Scholar for “blood group cancer” and “systematic review”, and here we see a review on this topic: this is a meta-analysis, we’ll talk about those in another video, but a meta-analysis in short is a sort of article that numerically aggregates individual statistical results from all the articles they could find, merges them with some statistical techniques as to have a sort of giant unique study that has a superior statistical “confidence” or strength. Reading this we find out that yes, indeed it looks like blood types are associated to a different risk of developing cancer, for instance type A is associated to an increase in cancer risk of 12% compared to non-A types, while type 0 is associated to a reduction of 16% compared to other types, but they vary based on the type of cancer: we talk about relative risk, so an increase or reduction in the base risk we all have, based on blood type. So, having a specific blood type influences our health: this article focused on cancer, others talk about other diseases, here we are not yet talking about diets, but since diet is somehow related to health, it is not totally impossible to have a correlation. After a first screening this theory is not entirely up in the air: it might, MIGHT, make some sense, so it is worth an investigation. What now? Let’s look for a systematic review studying the relationship between diet and blood type: it exists and was done in 2013; this review summarized what was known in 2013 about the relationship between diet and blood types it finds articles correlating cholesterol with bood types and other stuff, but the conclusions here are that, it is written explicitly: “for now there is no proof corroborating the supposed benefits of a blood type diet.” This is 2013; I’ll note that d’Adamo’s book is from 1996 and Mozzi’s book from 2012 so when they published their books there was no accepted scientific proof for the beneficial effects of these types. The article goes on, saying: “Right now there is no evidence that adherence to blood type diets will provide health benefits.” “Until the health effects of blood type diets have been substantiated, consumers should be aware that aware thataware that the advertised health benefits are not supported by scientific evidence.” So in theory it ends here! We should chuck all this in the bin. But no! Nope! As I said, a diet could make sense for the wrong reasons, and so it is right, it is worth looking into this, and therefore in 2014 inspired by the lack of studies on these diets, some researches spent time making a study 2014. How did I find this? Well, on Google Scholar if you look below the first article you can see all the subsequent articles that cited this, that referred to it, you click and you find the most recent articles citing this one, and you find this one too. It is a useful way to proceed starting from one article, perhaps quite old, up until modern times to see how a theory, a discussion evolved: they took 1455 healthy subjects and for one month they had to fill a questionnaire stating what they were eating, and they also measured the subjects’ cholesterol levels BMI, other measurements, they were especially interested in risk factors for cardio-methabolic diseases keep in mind, none of the subjects received a diet these researchers did things differently, they took these subjects, they analyzed what they were eating during one month, and they gave scores to what they were eating normally, and what they kept on eating, to see which of their diets by chance approached diets of type 0, or of type A, B and so on. All these diets share the fact that for one group there is a list of preferred foods a list of neutral foods and a list of “harmful” foods, then some foods are crossed off every diet regardless of blood type, e.g. soft drinks highly processed food and so on. So it might have occurred that somebody was already, of his own accord, following a diet type 0: maybe they ate meat every day, or maybe you could have had a vegetarian with a given intake pattern that automatically was following an A-type diet; then of course they used scores the article has more details, they gave a metric, a score defining how much your diet approached one of the types. So some people were already unknowingly following a type 0 diet, maybe others had a diet in between 0 and A, others were not following any of these diets, maybe they drank copious amounts of soda, hot dogs and fries every day – I am aware that this might be one of the most complex videos I have ever made, to explain what is a complex topic – if you are getting bored feel free to pause and watch the second part another time. So: if the blood type theory were right, people with blood type 0 that were of their own accord following a type 0 diet, should have been healthier, should have seen their blood parameters (cholesterol, insulin and so on) get better compared to those who were of type 0 but were adhering to a type A diet, and so on and so forth with all possible permutations this only if blood type diets made sense. What have the researchers found? They found that indeed there are benefits associated to adherence to a certain diet. For instance, those adhering to a type A diet, with less meat and more vegetables, had a lower blood pressure and a smaller waist, lower cholesterol and other measures that relate to cardio methabolic diseases. The funny thing is that this effect was entirely independent from the person’s blood type, so those adhering to a type A diet had better parameters both when they had type A blood, and when they had other types. There was absolutely zero correlation between the diet and the blood type. The researchers conclude that the results do not prove the advantages of blood type diets the study shows how following some diets is associated to a reduction in risk of cardio diseases and this explains the anecdotal evidence surrounding these diets, which are often conservatives and model healthy lifestyles, but there is no relationship with your blood type so, if these diets are beneficial this is not due to the fact that you are following a type A diet because you blood type is A: simply, the people following it feel better and associate this good result with a magical bond with the blood type, even though there is no correlation. A tombstone for this theory? Not yet: you know that scientists always go deep and try to eliminate every potential factor that we might have overlooked. This study here has two limitations: first, it has been done on healthy people, but one might say: “Well, but these diets are used by people who are sick, who have issues so let’s see what happens if we start with people who are overweight or obese or have diseases.” The second issue with this study is that it was not an intervention study, that is, researchers did not intervene to modify their diets: it is an observational study, they looked at what these people were to eat, measured a few things and made some correlations associations that, as you’ve seen and as I explained in another video do not always imply a cause-effect relationship. A study that modifies peoples’ diet and examines the supposed link with blood type has not been done until 2018. This article too was found by looking at who cited the 2014 article: right, in 2018 somebody made a study where they varied the diet of the people who participated in the study, and moreover the subjects were not healthy, they were overweight so they already had an increased risk of developing diseases such as cardio metabolic ones. These researches got together a thousand of overweight people in Canada so with an increased risk of developing some diseases such as the cardio metabolic ones; they measured their blood parameters, waist size, weight, BMI, cholesterol and other tests, observed what they were eating for a period, by having them fill questionnaires. Now, questionnaires are not the most faithful things, there are some problems, among others the nutritionist Stefano Vandrame discussed this on Youtube in a series of nice videos on the limitations of nutritional research, you can look them up. So what did they do? They told some of these people what they should eat to have a healthy and varied lifestyle, so they did not say “you do a type A diet, you do a type 0 diet”, this would probably not get approved by the ethical committees but anyway they told them: “try to eat this way”, giving suggestions for a healthy and varied diet, so less animal products, lots of fruits, raw and cooked vegetables, the famous “portions”, less free sugars, the usual stuff. Then for 6 months, 6 months, these people had more or less tried to change the nutrition habits at home, and again every day they had to write down what they were eating, how much and so on. After 6 months the researches took all the data, analyzed them exactly as it was done in the first article, they looked at those by varying their habits got closer to a type A diet, those who persisted in their old lifestyle without any change, those who got closer to a type 0 diet and so on, by the way that is not just eating meat all the time. The results were that, those who got closer to a type A diet, at the end of the intervention had a higher reduction in their BMI, basically they had lost more weight than the others those who had followed a sort of type B diet had a smaller waistline, and those who had followed a type 0 diet had still improved their blood parameters compared to previous analyses. But yet again, the researchers said, the improvements were independent of the blood type funny, right? So these improvements were due to the fact that likely they had bad food habits previously, perhaps they ate too much processed food, not enough fresh fruit and vegetables, they drank too much soda, lots of sugary drinks and so on, and so after varying their diet their parameters improved. So this lets us put a tombstone on the idea that your blood type could be in any way related to what we should eat, but we can draw some conclusions from this weird theory: first, human beings love stories, we love simple explanations and charming ideas those that join everything together and everything is in its place, and across centuries several funny ideas, even medical theories have been followed mostly thanks of their evocative power, analogies with other phenomena, and not because they were real solid scientific studies. Our psychological nature leads us to accept, to believe a nicely-written narrative rather than facts that sometimes lack a coherent story behind them and this is the opposite of science: in science, if I measure something, if I gather data and prove phenomena, I should accept them even if I cannot explain them, while actually we see a proliferation of pseudo-medicine, quirky diets with no scientific basis, but often they are embellished with charming stories, analogies with dubious natural phenomena, and of course all the marketing around these silly illogical pseudo medicines exploits all this, us humans are attracted by this, we love when they tell us a good story. Here this diet has a second advantage, an appeal, it offers you, with no cost, the idea that you can eat what is right for you. We do not like the idea of a statistics that covers all of us, no! I want to know what is best for me, we are individuals. What can be simpler than tying what I am, my blood group, with what I eat; if we want, it is the same basic idea that is used for all those tests – sadly sold even in pharmacies – where they tell you: through your DNA I will find your food allergies, or I can even analyze what you should eat; a custom diet based on DNA, there is absolutely no scientific evidence nothing accepted by the scientific community, but they are popular thanks to this appeal, they make you think that you are special and not a mass product: “you are you, I talk to you” and so eat this because it is right for you, do not eat that because it is wrong for you. The second thing we learn – a very sad thing if you ask me – is that we are unable to change our nutritional habits just thanks to suggestions: we need an external imposition, even better if this imposition incites emotions, tells us: “look, if you eat that, that is just right for you, you’ll feel great!” “but if you eat that you will be sick, it is bad for you!” and what is better than a verdict that appears to be scientific, based on blood types or DNA? All the suggestions on what to eat of the world health organizations, are undoubtedly boring, tedious, they tell you: “eat this, but in this amount, but don’t go over this other amount”. What do we know about the free sugars we actually eat every day? Many people find this difficult, I saw people that after my video on the free sugars and WHO literally panicked: “OMG I am drinking orange juice, it has free sugars!” no problem, there are limits, often we can eat something in a given range: there might be a minimum, or not, there might be a maximum, but what do we know? It is much more reassuring to hear something like: “eat chicory! don’t eat duck breast! eat liver! no radicchio! yes to coregonus!” (by the way that’s a fish). Much simpler! It is sad to realize that we are unable to follow on our own – some are able to, but not in the majority of cases – a varied and measured diet: measured means we only eat what we need – and nope! usually a portion of 120 g of spaghetti with carbonara sauce is not a measured portion! – and so we need some threat, some imposition from above; now, if you are among those, and I know there are many, who follow doctor Mozzi, some idolize him as if he were Osho and you are happy with your current diet, keep doing it! It is not my aim, not my purpose, not my job to convince you to change what you eat, absolutely not! Likely you felt worse before because you were eating crap, and if by following this quirky idea you learned how to change your food habits, if you started enjoying quinoa, liver and coregonus, variety in the kitchen is always good! Maybe on your own you would have never done this, you would have never learned to enjoy chickpeas or cabbage! As I said, all of these diets share, more or less, the exclusion of sugar drinks, of processed foods and so on, so we should not be surprised if somebody with with bad habits, feels better after changing them; the important part is to understand that this is not related to your blood type anyway I am not a dietist and it is not my purpose to give you diets or convincing you to change your food habits, but as a popularizer I tell you what the scientific research has found on the ties between diet and blood type, that is nothing. Thus, even if you are of type 0 like me, there is no scientific reason to run away from clam sauce spaghetti o Milano risotto, two of the things it is, IMHO, worth living for, and that your friendly neighbourhood chemist prepares very well and enjoys regularly, so bye bye and hope to see you again on the channel of your friendly neighbourhood chemist. Ciao!