How to feed your microflora?

The menu is selected by the bacterium

Alexandra Bruter, <url>Bacteria living in the gastrointestinal tract can influence the eating behavior of the host.

This hypothesis, based on a review of a large number of independent studies, was put forward by American scientists in their article in the journal BioEssays (Alcock et al., Is eating behavior manipulated by the gastrointestinal microbiota? Evolutionary pressures and potential mechanisms).

Cases when parasites influence the behavior of hosts, changing it to their advantage, are known to science. For example, toxoplasma, multiplying in an intermediate host – rats, makes it so that rats no longer feel fear at the smell of cat urine and become easy prey for cats. Cats are the main hosts of toxoplasmas, only in their body the parasite is capable of sexual reproduction. Therefore, toxoplasma does not really care about the lifespan of an infected rat – it is much more profitable for it to get into a cat as soon as possible. Moreover, the smell of cat urine causes sexual arousal in rats, as a result, the probability of the birth of already infected baby rats increases. Most often, however, parasites are interested in ensuring that their host does not die too quickly, and can give him advantages. A case of a parasitic crustacean is described, which causes the fish to always turn in the same direction. That is, the fish does not think, but immediately turns. This gives her a certain advantage, if necessary, to escape from a predator, and the crustacean – the opportunity not to think about finding new owners for a longer time. But we must understand that the behavior of the crustacean is never altruistic, it's just that their goals coincide with the fish this time.

The intestinal microflora is, of course, no parasites, but symbionts. But they may also have their own interests. In particular, they compete with each other. The human intestinal microflora is diverse and consists of different types of bacteria (the set of these species is individual for different people, as well as the ratio of the number of representatives of different species). Different species prefer different foods. Someone grows faster on hydrocarbons, fats are more profitable for someone, polysaccharides for someone. Microbes digesting these algae have been found in the bodies of some Japanese whose diet is rich in seaweed, and in the organisms of African children whose diet is based on sorghum, bacteria digesting cellulose. If one of the symbiont bacteria had learned to speak to the host: "Come on, eat immediately what is beneficial to me, but not to the neighbor," he would immediately receive an evolutionary advantage. The published work just provides evidence in favor of the fact that someone really learned this.

There is a study that shows that people who really like chocolate, the intestinal microflora differs from the microflora of people who are indifferent to chocolate.

Double-blind placebo-controlled clinical trials have shown that the use of the probiotic Lactobacillus casei leads to an improvement in mood in people with reduced mood. In similar animal experiments, it has been shown that this effect is mediated by the vagus nerve – if the vagus nerve is cut, no effect is observed.

Intestinal colic in infants is associated with the characteristic features of the intestinal microflora. They cause discomfort in children, making them cry, which leads to increased attention from parents and unplanned attempts to feed. In some cases, there was a connection between colic and too rapid weight gain. There is a hypothesis that the mechanism of this and similar effects is the production of toxins by bacteria that bind to pain receptors on the inner surface of the gastrointestinal tract. Toxins are produced only when the right food does not arrive. It has also been shown that hunger markedly enhances the perception of pain through the vagus nerve.

There is also evidence in favor of the fact that the composition of the intestinal microflora can affect the number and activity of food receptors on the tongue, and this is a sure way to influence food preferences in the right direction. It was noted that after some operations on the stomach, the composition and activity of these receptors in humans changed.

Probably, bacteria can influence the host's eating behavior with hormones. Serotonin and dopamine – derivatives of amino acids tryptophan and phenylalanine – are synthesized by bacteria of the gastrointestinal tract in an amount almost greater than in neurons. Different types of symbionts synthesize many molecules similar to the body's signaling molecules associated with hunger: leptin, ghrelin, etc. True, the body has methods of combating foreign signaling molecules – antibodies and enzymes that destroy them, but this may indicate that the struggle for their own interests on this front has been going on for a long time.

Some evidence suggests that probiotics contribute to weight loss. The more numerous any one species is, the stronger its lobby, and the more it can affect the host's body, causing an unhealthy bias in any one side of eating behavior. Therefore, the key to healthy eating behavior is a more diverse microflora with less representation of each species. The ancient Roman principle of "divide and rule" in action.

From all this, there are several conclusions that can be tested experimentally in the future. If they are confirmed, we will have to revise our views on eating disorders in many ways.

It suggests, in particular, the conclusion that eating behavior is contagious. There is already a study that has shown that relatives living under the same roof have a higher similarity of intestinal microflora than those living separately. It would be interesting to assess the similarities and differences in their eating behavior. Another study showed that the probability of getting fat increases by 57% if one of your friends has just got fat. That is, we are talking about an epidemic of obesity not figuratively, but in the most literal sense of the word. Being overweight can really be contagious.

But there is also good news. If the causal relationships described above are correct, then manipulations with the intestinal microflora should lead to normalization of eating behavior. There are also confirmations of this. For example, in animals, fecal transplantation from thin individuals with normal eating behavior to fat ones with abnormal leads to normalization of weight and eating behavior in the latter. Perhaps, based on this or some other methods of intestinal microflora transplantation, it will be possible to solve the problem of the obesity epidemic.

Portal "Eternal youth" http://vechnayamolodost.ru20.08.2014