It is hard to fool the brain by providing it with 'energyless' sweet flavours, according to new research in mice that suggests that consumption of zero-calorie sweeteners leads to higher sugar consumption later.
Published in The Journal of Physiology, the research findings suggest that our pleasure in consuming sweet solutions is driven to a great extent by the amount of energy it provides – revealing that greater ‘reward’ in the brain is attributed to sugars when compared to artificial sweeteners.
Led by Professor Ivan de Araujo from Yale University School of Medicine, USA, the research identifies a specific physiological brain signal that is critical for determining choice between sugars and sweeteners – and suggests that the metabolism of energy dense sugar (glucose oxidation) has control over the intake levels of sweet tastants by modifying levels of the dopamine in the brain.
"According to the data, when we apply substances that interfere with a critical step of the 'sugar-to-energy pathway', the interest of the animals in consuming artificial sweetener decreases significantly, along with important reductions in brain dopamine levels,” explained de Araujo.
"This is verified by the fact that when hungry mice – who thus have low sugar levels – are given a choice between artificial sweeteners and sugars, they are more likely to completely switch their preferences towards sugars even if the artificial sweetener is much sweeter than the sugar solution," he said.
The research was performed in mice, using a combination of behavioural testing involving sweeteners and sugars, whilst measuring chemical responses in brain circuits for reward.
The researchers believe their findings are likely to be reflected in humans.
"The consumption of high-calorie beverages is a major contributor to weight gain and obesity, even after the introduction of artificial sweeteners to the market,” de Araujo added. “We believe that the discovery is important because it shows how physiological states may impact on our choices between sugars and sweeteners.”
Specifically, the team said that their findings imply that humans frequently ingesting low-calorie sweet products in a state of hunger or exhaustion could be more likely to 'relapse' and choose high calorie alternatives in the future.
"The results suggest that a 'happy medium' could be a solution; combining sweeteners with minimal amounts of sugar so that energy metabolism doesn't drop, while caloric intake is kept to a minimum," said de Araujo.
Now that the team know that dopamine cells are critical in sugar/sweetener choice, they hope to identify the associated receptors and pathways in the brain, said the researcher.
Source: The Journal of Physiology
Published online before print, doi:10.1113/jphysiol.2013.263103
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