Why sweetener is no substitute for sugar in the brain

Sugar cravings can never be satisfied by artifical sweetener, as it is the calorie high, not the sweetness which keeps people coming back for more, scientists at Yale University have found.

For decades it has been a mystery why low-calorie sweeteners are simply not as rewarding as sugar – despite often tasting far sweeter per gram.

Now, a new study suggests that the brain responds to taste and calorie counts in fundamentally different ways.

And it is the brain’s desire for calories — not sweetness — that dominates our desire for sugars, according to the reserach in the journal Nature Neuroscience (click to read the paper)

“It turns out the brain actually has two segregated sets of neurons to process sweetness and energy signals,” said lead author Dr Ivan de Araujo of the John B Pierce Laboratory.

”If the brain is given the choice between pleasant taste and no energy, or unpleasant taste and energy, the brain picks energy.”

Both sweet taste and calorie counts register in the striatum, an ancient region of the brain involved in processing rewards.

The average Briton consumes 238 teaspoons of sugar each week – often without knowing it.

Humans have a sweet tooth as one way to ensure we eat enough to give our large brains enough calories to operate at peak efficiency.

However taste and nutrients are processed in different parts of the striatum – taste in the ventral striatum, and nutritional or calorie value in the dorsal striatum.

The researchers found that it is the signal about calories which has more control over eating behaviour. Mice fed sugar with a sweet taste but not calories or sugar with calories but no sweetness, preferred the latter.

“The sugar-responsive circuitry in the brain is therefore hardwired to prioritize calorie seeking over taste quality,” Dr de Iraujo said

The authors hope findings help spur new strategies aiming at curbing excess sugar intake.

Source: The Telegraph