Newsgroup: it.salute.alimentazione
Titolo: Lo zucchero puo' dare dipendenza?

XPOST it.salute.alimentazione,it.salute
Uno studio della Princeton University ipotizza, se ben capisco, la 
possibilità che il consumo di zucchero possa portare a una dipendenza 
fisica, con modifiche cerebrali di lungo termine... Lo studio è stato 
fatto sui topi, quindi vale per i topi. Però i ricercatori, nel 
comunicato della Princeton, prendono in considerazione anche la 
possibilità di meccanismi analoghi negli uomini, o per meglio dire in 
"some individuals with binge-eating disorder and bulimia": cioè, se ben 
traduco, alcuni individui con disturbi di alimentazione compulsiva e 
bulimia.
"It seems possible that the brain adaptations and behavioral signs seen 
in rats may occur in some individuals with binge-eating disorder or 
bulimia," Hoebel said. "Our work provides links between the 
traditionally defined substance-use disorders, such as drug addiction, 
and the development of abnormal desires for natural substances. This 
knowledge might help us to devise new ways of diagnosing and treating 
addictions in people."
Ovviamente la "pista" dell'abbuffata come "droga" è solo un'ipotesi da 
verificare e che, comunque, -bene ripetere a scanso di equivoci-, 
riguarderebbe al limite chi è soggetto a  "disordini 
dell'alimentazione", non chiunque metta due cucchiaini di zucchero nel 
caffè o mangi una fetta di panettone! Anzi, mi par di capire che i 
ricercatori pensino a meccanismi di  dipendenza da cibo in generale, 
non necessariamente ristretti allo zucchero...
Ad ogni modo, vediamo cosa è stato osservato nei topi. Alcuni topolini 
sono stati abituati a consumare zucchero in quantità, e su questi topi 
sono stati osservati sintomi di lungo termine di quella che secondo i 
ricercatori sarebbe una vera e propria "addiction": dipendenza, 
tendenza ad aumentare le dosi, alterazioni del comportament, e persino 
sintomi da astinenza quando vengono privati delle loro dosi di 
zucchero. I termini usati nell'originale sono "Craving and relapse" e 
"withdrawal", come elementi che caratterizzano l'"addiction".
La teoria circa il meccanismo alla base è che lo zucchero, aumentando i 
livelli di dopamina, provochi un'adattamento di lungo termine in alcuni 
recettori cerebrali.
Riporto dal comunicato della Princeton University:
[...]
Hoebel and his team also have found that a chemical known as dopamine 
is released in a region of the brain known as the nucleus accumbens 
when hungry rats drink a sugar solution. This chemical signal is 
thought to trigger motivation and, eventually with repetition, 
addiction.
[...]
After a month, the structure of the brains of these rats adapts to 
increased dopamine levels, showing fewer of a certain type of dopamine 
receptor than they used to have and more opioid receptors. These 
dopamine and opioid systems are involved in motivation and reward, 
systems that control wanting and liking something. Similar changes also 
are seen in the brains of rats on cocaine and heroin.
Siccome in questo campo è facile fraintendere le parole, mi sono 
cercato "addiction" sul Drug Medical Dictionary:
Definition of Addiction
Addiction: A chronic relapsing condition characterized by compulsive 
drug-seeking and abuse and by long-lasting chemical changes in the 
brain. Addiction is the same irrespective of whether the drug is 
alcohol, amphetamines, cocaine, heroin, marijuana, or nicotine. Every 
addictive substance induces pleasant states or relieves distress. 
Continued use of the addictive substance induces adaptive changes in 
the brain that lead to tolerance, physical dependence, uncontrollable 
craving and, all too often, relapse. Dependence is at such a point that 
stopping is very difficult and causes severe physical and mental 
reactions from withdrawal. The risk of addiction is in part inherited. 
Genetic factors, for example, account for about 40% of the risk of 
alcoholism. The genetic factors predisposing to addiction are not yet 
fully understood.
Source: MedTerms™ Medical Dictionary
http://www.medterms.com/script/main/art.asp?articlekey=10177
Ecco il testo del comunicato della Princeton:
Sugar can be addictive, Princeton scientist says
Animal studies show sugar dependence
A Princeton University scientist will present new evidence today 
demonstrating that sugar can be an addictive substance, wielding its 
power over the brains of lab animals in a manner similar to many drugs 
of abuse.
Professor Bart Hoebel and his team in the Department of Psychology and 
the Princeton Neuroscience Institute have been studying signs of sugar 
addiction in rats for years. Until now, the rats under study have met 
two of the three elements of addiction. They have demonstrated a 
behavioral pattern of increased intake and then showed signs of 
withdrawal. His current experiments captured craving and relapse to 
complete the picture.
"If bingeing on sugar is really a form of addiction, there should be 
long-lasting effects in the brains of sugar addicts," Hoebel said. 
"Craving and relapse are critical components of addiction, and we have 
been able to demonstrate these behaviors in sugar-bingeing rats in a 
number of ways."
At the annual meeting of the American College of 
Neuropsychopharmacology in Scottsdale, Ariz., Hoebel will report on 
profound behavioral changes in rats that, through experimental 
conditions, have been trained to become dependent on high doses of 
sugar.
"We have the first set of comprehensive studies showing the strong 
suggestion of sugar addiction in rats and a mechanism that might 
underlie it," Hoebel said. The findings eventually could have 
implications for the treatment of humans with eating disorders, he 
said.
Lab animals, in Hoebel's experiments, that were denied sugar for a 
prolonged period after learning to binge worked harder to get it when 
it was reintroduced to them. They consumed more sugar than they ever 
had before, suggesting craving and relapse behavior. Their motivation 
for sugar had grown. "In this case, abstinence makes the heart grow 
fonder," Hoebel said.
The rats drank more alcohol than normal after their sugar supply was 
cut off, showing that the bingeing behavior had forged changes in brain 
function. These functions served as "gateways" to other paths of 
destructive behavior, such as increased alcohol intake. And, after 
receiving a dose of amphetamine normally so minimal it has no effect, 
they became significantly hyperactive. The increased sensitivity to the 
psychostimulant is a long-lasting brain effect that can be a component 
of addiction, Hoebel said.
The data to be presented by Hoebel is contained in a research paper 
that has been submitted to The Journal of Nutrition. Visiting 
researchers Nicole Avena, who earned her Ph.D. from Princeton in 2006, 
and Pedro Rada from the University of Los Andes in Venezuela wrote the 
paper with Hoebel.
Hoebel has been interested in the brain mechanisms that control 
appetite and body weight since he was an undergraduate at Harvard 
University studying with the renowned behaviorist B.F. Skinner. On the 
Princeton faculty since 1963, he has pioneered studies into the mental 
rewards of eating. Over the past decade, Hoebel has led work that has 
now completed an animal model of sugar addiction.
Hoebel has shown that rats eating large amounts of sugar when hungry, a 
phenomenon he describes as sugar-bingeing, undergo neurochemical 
changes in the brain that appear to mimic those produced by substances 
of abuse, including cocaine, morphine and nicotine. Sugar induces 
behavioral changes, too. "In certain models, sugar-bingeing causes 
long-lasting effects in the brain and increases the inclination to take 
other drugs of abuse, such as alcohol," Hoebel said.
Hoebel and his team also have found that a chemical known as dopamine 
is released in a region of the brain known as the nucleus accumbens 
when hungry rats drink a sugar solution. This chemical signal is 
thought to trigger motivation and, eventually with repetition, 
addiction.
The researchers conducted the studies by restricting rats of their food 
while the rats slept and for four hours after waking. "It's a little 
bit like missing breakfast," Hoebel said. "As a result, they quickly 
eat some chow and drink a lot of sugar water." And, he added, "That's 
what is called binge eating -- when you eat a lot all at once -- in 
this case they are bingeing on a 10 percent sucrose solution, which is 
like a soft drink."
Hungry rats that binge on sugar provoke a surge of dopamine in their 
brains. After a month, the structure of the brains of these rats adapts 
to increased dopamine levels, showing fewer of a certain type of 
dopamine receptor than they used to have and more opioid receptors. 
These dopamine and opioid systems are involved in motivation and 
reward, systems that control wanting and liking something. Similar 
changes also are seen in the brains of rats on cocaine and heroin.
In experiments, the researchers have been able to induce signs of 
withdrawal in the lab animals by taking away their sugar supply. The 
rats' brain levels of dopamine dropped and, as a result, they exhibited 
anxiety as a sign of withdrawal. The rats' teeth chattered, and the 
creatures were unwilling to venture forth into the open arm of their 
maze, preferring to stay in a tunnel area. Normally rats like to 
explore their environment, but the rats in sugar withdrawal were too 
anxious to explore.
The findings are exciting, Hoebel said, but more research is needed to 
understand the implications for people. The most obvious application 
for humans would be in the field of eating disorders.
"It seems possible that the brain adaptations and behavioral signs seen 
in rats may occur in some individuals with binge-eating disorder or 
bulimia," Hoebel said. "Our work provides links between the 
traditionally defined substance-use disorders, such as drug addiction, 
and the development of abnormal desires for natural substances. This 
knowledge might help us to devise new ways of diagnosing and treating 
addictions in people."
News from PRINCETON UNIVERSITY
Office of Communications
http://www.princeton.edu/main/news/archive/S22/88/56G31/index.xml?section=newsreleases

 fisica
[MEGA-CUT]
Tempo fa ho letto un articolo in cui facevano riverimento al BED e alla 
leptina proprio sui topi, somministrando la loro scarsa quantità di questa 
sostanza prodotta riuscivano a fargli evitare craving. A dire il vero, più 
ne somministravano e meno mangiavano, anche tenendoli a stecchetto per poi 
dargli il cibo.
Comunque, io so che la candida dà dipendenza da zuccheri e può dare disturbi 
compulsivi.
Ergo, anche alimentari vedi BED e bulimia...
Sarebbe auspicabile uno studio in tal senso che comprenda più elementi, 
senza trascurare nulla.