Digging Into The Science Of Protein Cravings

When deprived of protein, specialized cells in our gut release a hormone telling our brain to crave food containing essential amino acids.

AsianScientist (Jun. 7, 2021) – If you’ve ever suddenly had cravings for meat or dairy, cells in your gut are likely telling your brain that you have a protein deficiency, found researchers from South Korea. Their findings were reported in Nature.

Whether you’re an adherent of intermittent fasting, keto or the latest trendy diet, the fact remains that all organisms require a balanced intake of carbohydrates, proteins and fats to function normally. After all, these biomolecules not only give us energy, but they’re also made up of building blocks that play crucial roles in everything from cell repair to hormone production.

“Taking in sufficient calories alone won’t do the job. If the diet does not include enough proteins, it can still lead to severe forms of malnutrition including kwashiorkor,” explained Professor Greg Seong-Bae Suh from the Korea Advanced Institute of Science and Technology (KAIST).

Though scientists have long known that inadequate protein intake causes organisms to crave foods rich in proteins or essential acids, the biochemical underpinnings of these cravings remain unexplored. To dig deep into the science of cravings, Suh and Professor Lee Won-Jae from Seoul National University (SNU) examined the effects of different genes on food preference in fruit flies after protein deprivation.

The team found that depriving flies of protein triggered the cells lining our intestines to release a hormone called CNMamide (CNMa). Previously, it was thought that these cells, called enterocytes, exclusively digested and absorbed food.

However, through neuropeptides like CNMa, enterocytes can convey the body’s nutrient status—or lack thereof—to receptors on our brain’s nerve cells. This action then triggers a sudden desire to eat food containing all the essential amino acids including egg, fish and meat.

Interestingly enough, the KAIST-SNU team also found that certain gut microbes, like Acetobacter bacteria, can temporarily produce amino acids to compensate for mild protein deficiencies. This base level of amino acids provided by the bacteria modifies the release rate of CNMa, lessening the flies’ desire to indulge in more protein-rich foods.

While further studies are needed to understand how exactly CNMa communicates with its receptors on the brain, the team’s research provides initial insights into why living things from fruit flies to humans love protein so much—and what happens when all that protein is taken away.

“We chose to investigate a simple organism, the fly, [to] make it easier for us to identify and characterize key nutrient sensors. 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,” concluded Professor Suh.

The article can be found at: Kim et al. (2021) Response of the Microbiome–gut–brain Axis in Drosophila to Amino Acid Deficit.


Source: Korea Advanced Institute of Science and Technology; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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