We humans have different types of blood, as well as different colors of eyes and hair. But why is this so? And does it make sense to stick to a diet consistent with your blood type?
Knock! Knock! Knock!
You are chopping an onion and suddenly the knife jumps off and leaves a decent cut on your thumb. Immediately, blood begins to flow - a red, sticky liquid that is in all of us, and it looks the same no matter who it belongs to.
But while the blood looks the same, there is a difference in its composition. Because people differ in blood types.
In this regard, one of our readers, Frits Møller, asks:
“I don’t quite understand why people have different blood types? What is the difference?"
Blood types are determined by genes
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Videnskab. dk referred the issue to two scientists, major experts in the field, Morten Hanefeld Dziegiel, MD, Ph. D. of the State Hospital Blood Bank, and Torben Barington, Professor and MD, University of South Danish. …
Morten Hanefeld Dzigel explained that blood types are determined by our DNA.
“Certain types of blood correspond to certain genes. In the course of our evolutionary development, human genes have mutated, which gradually led to changes in our genetic material. Thanks to this, among other things, different types of blood have emerged,”he says.
Professor Torben Barington clarifies that in the course of human development, without a doubt, there were many more ancient types of blood, of which now there is no trace left, since those genes were unsuccessful.
This development is constantly ongoing, and, in fact, the phenomenon of our different blood types is the key to the fact that we humans are still a successful species.
“In terms of development, the fact that we are different is an advantage. The more genetic variants there are among humans, the more likely we as a species will cope with disease, as it makes us more resilient,”he explained.
AB0 system and rhesus - most important in blood transfusion
Both scientists say there are many different types of blood that vary from person to person. To determine which type of blood we are talking about, there are 30 different so-called "blood group systems".
Two of these blood type systems are critical in relation to blood transfusion:
1. The so-called "System AB0" (pronounced AB-zero)
2. The so-called Rh factor
The "AB0 System" was invented in 1901 by the Austrian Karl Landsteiner and it was a pioneering invention.
It made it possible to divide all people according to their blood types - today the well-known groups A, B, AB and 0 (zero).
Another blood type system, according to the Rh factor, was invented around the years of the Second World War and is considered by doctors to be the second most important blood type system in connection with blood transfusions.
A person inherits a blood type from their parents
The genes that a person receives from his parents determine which blood type he will have. Namely, parents pass on their genes, which "encode" the type for AB0 and the Rh factor - for a gene from each parent, explains Torben Barington.
The genes that are responsible for A and B are equally dominant, while the gene carrying zero is recessive. Therefore, in order for a child to have blood group 0, it is necessary that both parents pass on the gene that is responsible for blood group 0 (see the picture above).
This means that if a person, for example, inherits a gene for blood type A from one parent and a gene for blood type B from another, then he will receive blood type AB, since A and B are equally dominant.
If a person inherits A from one parent and 0 from the other, then he will have blood type A, since A will suppress 0. Such dominance, however, does not exclude the possibility that he will pass the gene for blood type 0 to his children - this remains A 50 percent chance, explains Torben Barington.
The distribution of blood groups around the world varies
Blood types vary from people to people around the world. Denmark has the largest number of those with blood type A (44%). Next comes blood group 0 (41%) and B (11%), and blood group AB (4%) is the least common.
“The distribution of blood groups in the world may be due to the migration of peoples. We who live in Europe or Asia probably all come from small populations of people with relatively little gene diversity that came from Africa about 50,000 years ago,”says Morten Hanefeld Dzigil and continues:
"At some point in time, some groups went east, others west, and still others north, and over many generations these divided populations have evolved in their own way, with different blood types."
Mountain ranges and deserts could have had an impact
Therefore, the distribution of blood groups in one population is the result of the genetic variability of the original group of people; changes that happened as a result of natural selection, plus those genes that were obtained as a result of exchange with other populations. Mountains, deserts, seas or some other geographic obstacles could also affect the process, since this or that population could therefore be more or less isolated.
Isolated populations will have less genetic variation, which may help explain why, for example, the indigenous population of the Indians of Peru and Brazil only has blood type 0.
In general, blood group 0 in about half of all people on earth, but towards the east through Central Europe and Asia, group 0 is becoming less common, and B and AB more often. For example, 30% of Asians have group B.
There is no evidence to suggest a blood type diet
Some people would gladly use their blood type information for health care purposes. Recently, a new concept of nutrition has appeared, according to which it is beneficial for health to eat in accordance with your blood group.
One of our readers, Lasse Kandler, would like to know if there is some truth to this new mania:
“What evidence is there that blood type and diet have an effect on each other?” He asks.
Morten Hanefeld Dzigil from the Blood Bank would not argue that there is even a grain of truth in this opinion.
“I have not dealt with this issue, but it seems to me that this is a fantasy. From my point of view, the claim that blood groups play a role in this is just a random invention about the variability of people."
No need to build a diet based on blood type
“Rather, it is about the fact that our food and environmental conditions were favorable for people with certain traits. They allowed us to be resistant to certain things, and our bodies to absorb certain foods. We Europeans, for example, have grown accustomed to processing sugar in cow's milk over many generations as adults. In contrast, in Africans, cow's milk causes diarrhea. But I don't think it has anything to do with the blood type,”he says.
Professor Torben Barington agrees with Morten Hanefeld Dzigil. He adds:
“This opinion is absurd, there is no scientific reason to say that our blood type says anything about what we should eat. I would not recommend that you base your diet based on your blood type."
Faith can move mountains
When someone says a Blood Type Diet works for them, it could be due to several factors, Torben Barington explains.
"First, as with many things, faith can move mountains, and the human brain is designed so that when we experience two things that coincide in time, we tend to think that there is a causal relationship between them."
“This requires an objective survey of many people to determine whether it is an accident or not. But it seems to me that many in such a group can agree that something is happening in a certain way - when scientific research will show the opposite,”he says.
Diet changes work on their own
He adds that dietary changes in and of themselves can be beneficial for many people as they become more attentive to it and eat healthier foods. This fact may help explain what may seem like the right diet for your blood type.
“When things are bad at the start, the end result is usually better if you do something. If, for example, you have digestive problems, changing your diet can have a healing effect. However, it has not the slightest connection with the blood group,”says Torben Barington.
Videnskab. dk thanks Morten Dzigil and Torben Barington for their help. And also thanks our inquisitive reader.
If you yourself have any questions - both big and small, then you can send them to us at sv @ videnskab. dk. You can also read answers to other good questions in the Spørg Videnskaben section.
Blood groups in animals
Different species of animals have different blood groups, but not all species have been studied yet. Copenhagen Zoo veterinarian Mads Bertelsen told us about this.
Antigens of the human ABO blood group system have also been found in monkeys such as chimpanzees, bonobos, and gorillas, but their blood types are not identical to humans. Therefore, it will not be possible to carry out blood transfusions between monkeys and humans, in addition, monkeys carry various viruses that can be transmitted to humans.
The reasons why animals have developed different blood types may well be the same as in humans, said Mads Bertelsen.
"It is likely that the different blood types within the same animal species are due to the fact that this makes the species more resistant to disease, and therefore, of course, there are many more blood groups in animals than we have managed to establish to date."
Dogs get blood transfusions too
In addition to determining the blood groups of some species of monkeys, the blood groups of dogs, cats and horses have been studied.
“Dogs have eight internationally recognized blood types that are used when a dog needs a blood transfusion,” says Mads Bertelsen.
Blood transfusions are also given to cats, horses and cows. Three different blood types were found in cats, while horses and cows had eight and eleven blood types, respectively. And pigs were found to have 15 blood groups.
The blood types of birds, fish and reptiles have not yet been studied, according to Mads Bertelsen.
“But I’ll be very surprised if these species don’t have different blood types,” he says.
Ditte Svane-Knudsen