Craving meat? It may be your gut talking
Have you ever had a sudden desire for meat or dairy? Researchers from South Korea have discovered the reason behind these sudden cravings, reported in Nature.
All organisms - including people - require a balanced intake of carbohydrates, proteins and fats to keep functioning normally, and these biomolecules work as both an energy source and the building blocks involved in cell repair, hormone production and other important bodily functions.
“Taking in sufficient calories alone won’t do the job,” said Professor Greg Seong-Bae Suh from the Korea Advanced Institute of Science and Technology (KSAT).
“If the diet does not include enough proteins, it can still lead to severe forms of malnutrition including kwashiorkor.”
To determine the mechanisms behind these cravings, Suh and Professor Lee Won-Jae from Seoul National University (SNU) looked at how different genes affected the food preferences of fruit flies that were deprived of protein.
Gut-brain communication
The researchers found that a hormone called CNMamide (CNMa) was released from the cells lining the intestines of protein-deprived flies.
These cells, called enterocytes, were previously thought to solely digest and absorb food.
But, enterocytes can use CNMa to communicate the body’s nutrient status - or what it’s missing - to receptors in the brain’s nerve cells. This then triggers a sudden desire to eat food that contains all of the essential amino acids that are missing, which are found in eggs, fish, and meat.
Bacteria lend a helping hand
The team also found that certain gut microbes can compensate for mild protein deficiencies.
Acetobacter bacteria, for example, can temporarily make amino acids the body is lacking, leading to a decrease in the amount of CNMa released and a drop in the flies’ desire to eat protein-rich foods.
Why this matters
Though the exact way that CNMa communicates with the brain receptors is unknown, these findings serve as a first insight into why living things need and want protein so much - and what can happen if it’s taken away.
“We chose to investigate a simple organism, the fly, [to] make it easier for us to identify and characterise key nutrient sensors,” Professor Suh said.
“Because all organisms have cravings, the nutrient sensors and pathways we identified in flies would also be relevant to mammals. This research will greatly advance our understanding of the causes of metabolic disease and eating-related disorders,” he concluded.