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expert reaction to new research into the taste of beer and the desire to drink more

A study published in the journal Neuropsychopharmacology suggested the flavour of beer alone may activate a brain region that provokes the urge to become intoxicated, and futhermore that this effect may be stronger in people with a genetic predisposition for alcoholism. 

 

Prof David Linden, Professor of Translational Neuroscience, Cardiff University and Co-leader of the MRC Addiction Research Cluster Applied Cognitive Neuroscience, said:

“This study of the release of the neurotransmitter dopamine in response to beer flavours uses an interesting methodology to assess people’s motivational responses to alcohol cues. Alcohol abuse is a major public health concern, and it would be of great interest to have markers of predisposition to problem use of alcohol to enable early intervention.

“However, the presented effects are small and results have to be considered as preliminary, and the higher release of dopamine to beer compared to Gatorade flavours was not associated with actual drinking behaviour or dependence.

“We are thus still very far away from understanding the biological processes that contribute to risk of alcohol abuse.”

 

Professor Peter Anderson, Professor of Substance Use, Policy and Practice, Newcastle University, said:

“It is well known that all sorts of cues, including taste, smell, images, and habits (e.g. one always has a drink after work) raise desire for drinking.  This desire often appears to be dose dependent – meaning larger when average consumption is larger. This paper demonstrates that taste alone impacts on the brain functions associated with desire. This is not surprising – if taste increases desire, it has to impact on brain functions.

“With regard to the family history effect, this is quite difficult to assess and know what it means so we can’t be too sure of an effect or how strong it might be.  

“Finally, in my view, a direct pharmacological effect cannot be ruled out. In evolutionary terms, humans, as for primates and other mammals, were exposed to small doses of ethanol through eating ripe fruit that had fermented. There may have been some evolutionary advantages for this, and this is why we have the biochemistry to metabolize ethanol.  But, the doses would have been small and we would have been able to detect them and we would have biologically reacted to them.  In the present study, the subjects were exposed to about 12mg of ethanol over a 15 minute period – possibly enough for a direct pharmacological response.”

 

Professor Dai Stephens, Professor of Experimental Psychology, University of Sussex, said:

“This paper reports that in non-dependent experienced drinkers, the flavour of beer is able to increase dopamine in the ventral striatum, in a way similar to, though not to the same extent, as alcohol itself.  These findings, though neatly done, and a first convincing demonstration in humans that a drink’s flavour has such effects on the brain, are not particularly surprising as we have known for some time from animal studies that events conditioned to drug taking come to increase dopamine. And, while suggestive, the findings cannot with certainty be ascribed to conditioning. However, more provocatively, the study also suggests that not all beer drinkers show the same effect. Surprisingly, only those individuals who had close family members diagnosed for alcoholism showed dopamine increases in response to beer taste, raising the question whether a heightened conditioning, or an unusual ability of conditioned rewards to increase dopamine activity, underlies the development of alcohol (and perhaps other drug) abuse.

“Equally importantly, we know that exposure to such conditioned rewards is sometimes the trigger that induces abstaining addicts to relapse. Understanding the mechanisms that account for the differences in the consequences of this kind of conditioning between individuals at risk and not at risk for alcoholism might point to ways of reducing such risks.”

 

Further information from Professor Dai Stephens:

In Pavlov’s famous findings from over a century ago, occurrences meaningless in themselves (ringing a bell) after a few pairings with a significant event (delivery of food to a hungry dog) came to elicit similar physiological consequences (salivation) even if no food was delivered. This phenomenon is called Pavlovian conditioning, after its discoverer. It is not only physiological processes that can be conditioned, and, in a similar fashion, we have known for many years that similar meaningless events can become desired if they are repeatedly paired with something that is intrinsically rewarding. Wine drinkers often have collections of glasses way beyond their needs to serve dinner guests, and pipe smokers used to create collections when, for smoking purposes,  a single pipe would suffice. Sometimes, even mildly unpleasant occurrences become desirable if they predict something pleasant. Many of us who drink beer will remember that when we first sampled it, the taste was unpleasant.  Nevertheless, people who drink beer come to like the taste of beer, and, for some people, in the absence of anything better, the taste of even alcohol-free beer is better than nothing at all. How does this happen?

Pleasant events, and especially abused drugs, increase the activity of nerve cells that use the chemical messenger dopamine, in a part of the brain called the ventral striatum. Measuring this increase in people is difficult, so scientists have resorted to an indirect way. When dopamine is released from nerve cells, it passes on its message to the next nerve by docking at specialised proteins. Drugs related to those used for treatment of schizophrenia also bind to the same proteins, and compete with dopamine for these docking sites. So the more dopamine there is, the less chance the drug has of finding a parking space. Using brain scanners, and a radioactive form of the drug, scientists can measure the amount of the drug that is able to dock, and thus calculate how many docking sites are already occupied by dopamine, a reflection of how much dopamine is circulating nearby. Abused drugs (including alcohol) lower the binding of the competing drug, in correspondence to their ability to increase dopamine. 

 

‘Beer flavor provokes striatal dopamine release in male drinkers: mediation by family history of alcoholism’ by Brandon Oberlin et al. published in Neuropsychopharmacology on Monday 15th April.

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