New research is offering promising new paths to reducing sugar overconsumption.

Scientists in the States have shown that the brain responds not only when sugar touches the tongue but also when it enters the gut.

And it is this mechanism that explains why artificial sugar can never quite successfully replicate sugar.

The discovery of this specialised gut-brain circuit offers new insight into the way the brain and body evolved to seek out sugar.

As artificial sweeteners do not activate this circuit, the study also offers compelling evidence as to why these sweeteners are never quite as satisfying as the real thing.

The authors suggest this could pave the way for the creation of sweeteners that don't just trick our tongue but also our brain.

The team found that when the tongue encounters a taste, specialised cells on the tongue called taste receptors send hardwired signals to the brain.

Artificial sweeteners, such as NutraSweet and Stevia, work by co-opting these hardwired signals. They switch on sweet taste receptors to fool the brain into thinking that sugar has landed on the tongue.

When the sweet taste receptors are deleted in mice, which should have eliminated the animals' desire for anything sweet, the animals still display a preference for sugar. The research team's goal was to was to find out why and how, and to uncover the neural basis for our insatiable desire for sugar.

In a series of experiments in mice, the scientists developed techniques to monitor the real-time activity of cells in the vagus nerve. The team observed how these cells' activity changed when sugar was delivered into the animals' gut.

The author said that by recording brain-cell activity in the vagus nerve, they were able to pinpoint a cluster of cells in the vagus nerve that respond to sugar and saw, for the first time, sugar-sensing via this direct pathway from the gut to the brain."

Further experiments revealed the circuit in greater detail. Inhibiting a specific sugar-transporting protein in the gut eliminated the animals' neural response to sugar, showing that this protein, called SGLT-1, is a key sensor transmitting the presence of sugar from the gut to the brain via what is known as the gut-brain axis.

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