When we plan to lose weight, one of the first things we do is declare war on carbohydrates in the diet, reducing them as much as possible. All of this is often conditioned by the ‘advice’ seen on social networks in blogs, and which can have severe conditions, as reported in an article published in Nature Microbiology that suggests that this type of diet can end up increasing the risk of suffering from colorectal cancer.
The study. Researchers, conditioned by the increase in the number of people who decide to give up carbohydrates because they associate it with weight gain, wanted to test what was happening in a series of mice. In this way, an investigation was created with three different diets: a normal diet, one low in carbohydrates and another Western-style diet with a large amount of fat and carbohydrates.
The result. After exposing the mice to these conditions, they analyzed their microbiota, discovering a particular strain of E. coli bacteria, which was producing a DNA-damaging toxin called colibactin. A toxin that, in combination with a diet low in carbohydrates and soluble fiber, promotes the growth of polyps in the colon, which may be the first step to cancer.
As recognized by the researcher himself, Alberto Martín, professor of immunology at the Temerty Faculty of Medicine at the University of Toronto, it was initially thought that colorectal cancer was caused by a combination of different factors such as diet or genetics. But now a door is opening that means that a specific diet can lead to our bacteria enhancing the appearance of cancer.
Because. Researchers found that a diet deficient in fiber increases inflammation in the intestine and alters the community of microbes that reside here, which offer us many benefits and about which we are increasingly beginning to know more. Specifically, they focused on E. Coli that produces colibactin as we have discussed before, but what is really important here is that the mice fed a low-carbohydrate diet had a thinner layer of mucus that separates the intestinal microbes from the epithelial cells of the colon.
A priori, this mucus barrier that we have in the digestive system acts as a layer of protection that allows bacteria not to come into direct contact with epithelial cells. But if this shield is thinner due to this poor diet, more colibactin can reach the colon cells directly and act as an epigenetic mechanism that alters their structure and drives the deregulation of the factors that control their cell cycle.
But the researchers wanted to go a little further, by analyzing the effects on mice that had genetic mutations in their cells in the pathway responsible for repairing the damage that occurs in DNA. In this case the effect was very clear: the repair of these damages was not favored. This means that all the failures that are generated daily in our cells are not repaired or that the cell simply cannot enter apoptosis (programmed cell death) through these pathways. Something that adds ‘papers’ to have a cancer cell that gets out of control.
Lynch syndrome. A genetic health problem that causes the patient to have a greater chance of developing certain types of cancer, including colorectal cancer. All this due to mutations in genes that repair DNA, such as MLH1 and MSH2, among others. In this way, if a carbohydrate-deficient diet is added to these people who already have a higher probability of suffering from colon cancer, the effect of colibactin will increase these probabilities.
That is why the findings made by researchers suggest that people with Lynch syndrome who harbor these colibactin-producing bacteria should avoid stopping carbohydrates so as not to increase the risk. They even suggest that they can take specific antibiotics for these colibactin-producing bacteria to further reduce the risk.
Probiotics. When taking antibiotics, I’m sure that on more than one occasion you have been recommended to take probiotics in order to maintain the intestinal microbiota during treatment. In this case, research suggests that a strain of E. coli called Nissle that produces colibactin is found in these probiotics, which makes us ask many questions about its effect on cancer.
In this way, his laboratory is investigating whether long-term use of this probiotic is safe for people with Lynch syndrome or for those who follow a low-carbohydrate diet.
The antidote. Given all this, the question is obligatory: how can I avoid this if I have to consume few carbohydrates? To this end, the study has been able to see a correlation between the increase in soluble fiber in the diet with a decrease in the levels of colibactin-producing E. Coli. This is something that translates into less interaction with DNA repair mechanisms and therefore a lower probability of suffering from cancer.
“We supplemented fiber and saw that it reduced the effects of the low-carbohydrate diet (…) Now we are trying to find out which sources of fiber are most beneficial,” says Bhupesh Thakur, postdoctoral fellow and lead author of the study.
A treatment. The goal right now is to try to counteract the increased risk of cancer due to this bacterial toxin. To this end, the use of inulin is being investigated, which has been seen to reduce the amount of E. coli, which produces colibactin, and improves intestinal health in high-risk people. A treatment that, as it could not be otherwise, is focused on the fiber itself, which will become the best ally in these situations.
Imágenes | engin akyurt National Cancer Institute
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