Want to eat meat? Your gut flora and brain are in charge of this

Animals need a balanced intake of nutrients such as carbohydrates, proteins and fats to maintain health.

Meat is rich in protein, but if you consume too much, it will be harmful to the human body because in addition to protein, it contains a lot of animal fat and cholesterol.

Excessive protein contains a lot of nitrogen, which is decomposed by deamination and turned into urea and excreted in urine. This process requires a lot of water, which will increase the burden on the kidneys, and the harm will be greater if the kidneys are not in good condition.

Eating too much meat will result in excessive intake of sulfur-containing amino acids, which will accelerate the loss of calcium in the bones and lead to osteoporosis.

But if the diet is not protein-rich, it will lead to severe malnutrition. However, when protein intake is insufficient, animals will actively choose foods rich in protein or essential amino acids.

A study from the Korea Advanced Institute of Science and Technology and Seoul National University found that fruit flies' food choices are influenced by a "dialogue" between the intestines and the brain, regulating their desire for foods rich in protein or essential amino acids.

In fruit flies, the gut bacteria-gut-brain axis, commonly known as the bacteria-gut-brain axis, can detect whether essential amino acids are deficient and stimulate the fruit flies' desire for these amino acids.

Scientists have known that when an organism does not get enough protein, it will preferentially choose foods rich in protein or essential amino acids, but they are not sure how this happens.

Protein starvation in fruit flies triggers the release of a gut hormone called the neuropeptide CNMamide (CNMa) from specific intestinal cells. CNMa signals the nutritional status of the gut to the brain, triggering the desire to eat food containing essential amino acids.

They also found that gut bacteria - Acetobacter bacteria - produce amino acids that can compensate for slight protein deficiencies in the diet.

Supplementing this bacterium alone can produce amino acids that can alter the release of CNMa and alleviate the fruit fly's desire to "eat meat."

However, gnotobiotic flies carrying mutant gut bacteria that do not produce leucine or other amino acids showed higher CNMa expression and greater appetite.

Enterocytes sense amino acid levels from the diet and gut bacteria and communicate amino acid deficiencies to the brain via CNMa.

Therefore, there may be a similar mechanism in the human body, that is, your desires are not necessarily controlled by you, and your intestinal microorganisms may also be involved. There is a more detailed explanation in the section on desire in my course.

References:

Boram Kim et al. Response of the microbiome–gut–brain axis in Drosophila to amino acid deficit. Nature, 2021, doi:10.1038/s41586-021-03522-2.