In 2015 the World Health Organization (WHO) published a report concluding that red meat was “probably carcinogenic to humans”. An announcement that did not do more than to condense the wide scientific literature that relates the high consumption of red meats with the incidence of cancer, in particular, of colorectal type.
Also, a variety of studies find a relationship between sugars and the incidence of cancer as well as inflammation of tissues, although scientists do not know exactly why.
A sucrose substance, called Neu5Gc, present in many animals, but not in all; It is directly related to inflammation, arthritis and even cancer. Of course, only in those animals that do not have the gene that codes it, CMAH, including the human being.
In the absence of this gene, the presence of Neu5Gc in the body is considered a strange presence, which is detrimental to human health.
Now we know which animals have harmful sugar and which are not thanks to a study by the University of Nevada, in Reno (United States), led by the Spanish David Álvarez.
A finding that can be key to identify which animals are more suitable for human consumption; as well as which ones may be most suitable for organ transplantation.
The main researcher, David Álvarez, a computer biologist and PhD in genetics, has detailed to Muy Interesante what the study consisted of: “Through bioinformatics, we have developed a kind of genealogical tree of the evolution of this gene analyzing 322 genomes, identifying this gene in some animals in which it was unknown that it existed.“
The gene that got lost along the way
About two million years ago, our ancestors lost the CMAH gene, responsible for encoding the Neu5Gc sugar. Therefore, now the presence of this sugar in the human body is considered “a strange substance”, with consequent consequences for human health; and the same thing happens with other animals.
Thus, the team has discovered new animals that have lost this gene at some point in their evolution and are free of harmful sugar, as happened to humans.
They include two groups of bat, one type of whale, one type of deer, one type of amphibian called axolotl, one type of hedgehog, one type of reptile and the platypus; besides those animals that were already known to be devoid of this gene and that, therefore, are more apt for human consumption, like all birds or ferrets.
On the other hand, the cow, the lamb and the pig, but also several types of fish and other animals own the gene and, therefore, the Neu5Gc sugar. “By consuming their meat, the human being acquires this sugar and is toxic to us.”
Of the fish, it is known that many of them possess in gene in few quantities; however, “caviar does have high concentrations of Neu5Gc, although not so much in meat,” says Álvarez.
On the other hand, the mice do have this type of sugar, unlike the human; which can become a bias when it comes to creating mouse models for the study of pathologies, especially in cancer. “Depending on the research, we should use animals that do not have this sugar, creating models of the animal that we have eliminated the gene in question,” reveals Alvarez.
The presence or absence of this gene seems totally random. “We have not been able to understand why some species have lost the gene and others, not,” explains Álvarez, who acknowledges that future research should be devoted to this field of study.
Regarding human beings, there are several hypotheses to explain why the ability to synthesize this sugar was produced thanks to the CMAH gene.
“The most widespread postulate that this gene was lost because it made us more vulnerable to certain diseases, such as a strain of malaria that does affect other animals, such as chimpanzees and gorillas,” says the researcher.
A malignant sugar, only for some
Neu5Gc comes from another more primitive sugar, Neu5Ac, which is present on the surface of cells; This previous sugar acts as a code or language between cells, which serves to recognize each other.
Although Neu5Gc is similar, it is toxic to us, simply because we do not have the gene that encodes it. However that does not mean we can not synthesize it. In fact, in the human organism there are small concentrations of this substance, which is assimilated in the tissues; hence the damage it produces.
Although it is related to a higher incidence of cancer, among other conditions, it does not mean that it is totally toxic. “The body can survive healthy perfectly with low doses of this sugar, yes, in small amounts.”
Now, is the presence of this sugar that catalogs animal products as red or white meats ?
Not quite. According to Álvarez, they are different classifications. In fact, some parts of the pig are considered white meat, although the whole animal has high concentrations of harmful sugar.
In addition, this fact contravenes a recent trend in transplants: to try to make pig organs the ideal candidates for transplants.
In the same way, fish are not considered red meat, but according to the recent research, some of them have it, and others do not.
Therefore, animals that, like humans, do not have Neu5Gc sugar naturally in the body would be the most suitable for consumption, such as birds.
However, in the near future it would be possible to create transgenic animals by eliminating this gene from their organism, adapting them for human consumption without negative consequences for health.