What makes us crave for chocolate and lollies? Is it just the sweetness of desserts or something more? It has been proven that animals develop preference for sugar even if they are lacking in sweet tasting receptors which suggests that there is more to sugar cravings then just its sweet taste.

A recent research by Charles S. Zuker and colleagues from Columbia University in New York, was published in the journal Nature exploring this mechanism where a gut- brain connection is suggested to be involved in our preferential sugar consumption. They identified that a set of neurons in the brain particularly, vagal ganglia and brainstem are activated to create preference for sugar. According to this research these neurons are activated by sugar directly in the gut but not by artificial sweeteners. The vagal neurons are activated by glucose in the intestine. The researchers genetically silenced this communication between the gut and the brain in mice, which abrogated the sugar preference behaviour.

What is the purpose of a gut to brain sugar signaling system?

Glucose in the gut sends signal to brain. This suggests that signaling from the gut happens after sugar reaches its desired target for effective absorption and metabolic consumption. The sense of taste and activation of the gut- brain axis by sugar corroborates a strong and sustained preference for sugar rich foods. This seems to be an evolutionarily conserved phenomenon where sense of taste and nutrition combine to render a preference for certain foods. It would be interesting to see if other food preferences also utilize a similar gut brain axis.

The key finding in this paper is the authors were able to switch the sugar preference by activating the gut-brain axis using other chemical agents instead of sugar.

Of interest, artificial sweeteners which have been used widely in consumer products more than four decades have had negligible impact in decreasing sugar consumption and craving. This may now be understood at the gut- brain circuit level and could be indicative of a possible research in the future to develop a new class of sweeteners that activate both the sweet-taste receptor in the tongue and the gut–brain axis, and consequently help to moderate the strong drive to consume sugar.