It's Official: Junk Food IS Addictive
.jpg)
A couple of recent studies - one involving humans and another involving rats - have given extra weight to the notion that junk food is as addictive as cocaine or amphetamines.
The human junk food study
In one study by Dr Eric Stice and his team of psychologists at the University of Oregon, published in the Journal of Neuroscience, the chemical processes triggered by the high quantities of fat, sugar and salt hidden in foods such as burgers and milkshakes were found to produce the same sort of cravings as hard drugs, tobacco or alcohol.
Using brain imaging and genetic studies to compare obese and lean individuals, the researchers found that the same biochemical pathways were involved in responses to junk food and substances that are recognised to be highly addictive.
The mechanism involves stimulation of pleasure sensors buried deep within the brain known as dopamine D2 receptors. Dopamine is a neurotransmitter and hormone which is released as part of an inbuilt reward circuit for survival behaviours such as eating, sex and breastfeeding.
The amount of pleasure derived from eating correlates with the amount of dopamine released. Evidence from these studies shows that obese individuals have fewer dopamine (D2) receptors in their brains relative to lean individuals and that they may overeat in order to compensate for this deficit. Whether these individuals have an inherited deficiency of dopamine receptors or whether it has been induced by overeating is not clear.
"You see an initially elevated response in the reward circuitry; but then it reduces. As people overeat, their brains become desensitised to food clues, and that produces weight gain."
Dr Eric Stice
Constant or excessive stimulation of the dopamine cell receptors mean that these receptors become down-regulated by the cells involved. This means that either their sensitivity is reduced or their actual numbers are reduced in order to protect the cell from overstimulation. When this occurs, more junk food is required to achieve the same pleasurable feelings of satisfaction and the weight piles on.
The rat junk food study
In another unrelated study published in the journal Nature Neuroscience, researchers Professor Paul Kenny and Paul Johnson of Florida Scripps Research Institute, Florida found rats used to an unhealthy junk food diet voluntarily starved rather than eat healthy food.
The researchers fed rats on healthy food or healthy food plus unlimited access to junk foods and within a short period of time, the rats with access to the junk food began to eat compulsively and quickly became overweight eating twice as many calories as the rats on the healthy diet.
The researchers theorised that the rats had become addicted to the dopamine released when eating the junk food. In order to test their theory, they took the rats from the first experiment and hooked their brains up to a device that directly stimulated their D2 receptors when they ran on a wheel. Rats exposed to the junk food diet ran on the wheel for longer than those on a normal diet, suggesting that their D2 receptors had become desensitised.
In another test of the dopamine addiction hypothesis, the researchers blocked the D2 receptors in healthy rats who rapidly became compulsive eaters. Further, in the interests of true scientific investigation they demonstrated that even when being electrocuted whilst eating junk food, the addicted rats kept eating.
The truly shocking part of this is that the profound desensitisation of their pleasure response occurred after just five days of eating a junk food diet. Some fear that some of the biochemical changes induced might be permanent, although more research is needed.
Other research has corroborated the findings of these two studies with a report published in the Journal of Psychoactive drugs identifying a link between an inherited resistance to dopamine and addiction to sugar and alcohol. This may explain why even when people know all the facts, they still seem unable to combat their addiction to junk food.
About dopamine
Dopamine is one of the neurotransmitters produced primarily by the adrenal glands and the nervous tissue of the body and the nerves which produce dopamine are referred to as dopaminergic. Dopamine receptors are found throughout the brain, in the hypothalamus and in some other body tissues such as the heart, kidneys and immune cells.
Dopamine regulates many functions in the brain including:
-
Behaviour
-
Cognition
-
Voluntary movement
-
Motivation
-
Punishment and reward
-
Sexual function and gratification
-
Sleep
-
Perception of pain
-
Mood
-
Attention
-
Memory and
-
Learning.
Dopamine disorders are associated with a decline in memory, attention and problem-solving and are thought to contribute to conditions such as attention deficit disorder (ADD), schizophrenia, autism, and drug and alcohol abuse.
Drugs such as amphetamines, heroin and cocaine exert their pleasurable effects by increasing dopamine levels over tenfold. This causes flooding of the nerve synapses with dopamine, but a lesser effect is also obtained with alcohol and nicotine. Psychosis and schizophrenia are known to be caused by excessive dopaminergic stimulation and anti-psychotic medications act largely as dopamine antagonists.
Excessive stimulation of the dopamine receptors results in down-regulation and this may result in experiencing reduced motivation, a lack of pleasure, a shortened attention span, weight gain, fatigue, sexual dysfunction, drug-seeking behaviour and in becoming diabetic.
Conversely, understimulation of dopamine receptors may result from the presence of toxic metals such as mercury and this can cause the symptoms listed above associated with downregulation in addition to being a known cause of Parkinson's disease in which the affected person becomes unable to coordinate movement.
In fact, so profound is the effect of dopamine upon human behaviour that some authorities suggest that one of the primary differences between modern humans and our forbears was a transition towards becoming high-dopamine as a result of eating more meat.
Lawyers such as Professor Banzhaf of public interest law at George Washington University are already planning action against the food industry on behalf of people suffering obesity-related diseases stemming from childhood consumption of junk food based upon these findings.
In another unrelated study into rats and junk food, published in the journal Nature Neuroscience, researchers Paul Johnson and Paul Kenny in Florida Scripps Research Institute, Florida rats used to an unhealthy junk food diet voluntarily starved rather than eat healthy food.
The researchers fed rats on healthy food or healthy food plus unlimited access to junk foods and within a short period of time, the rats on the junk food diet began to eat compulsively and quickly became overweight eating twice as many calories as the control rats.
Since dopamine can also be released by pleasurable activities such as food or sex, Kenny and Johnson speculated that food addiction could develop in the same way.
To test whether the rats had, in fact, become habituated to dopamine, the researchers took the rats from the first experiment and hooked their brains up to a device that would directly stimulate their D2 receptors when they ran on a wheel.
Rats eating a junk food diet ran on the wheel significantly longer than rats fed a normal diet, suggesting that their receptors had indeed become desensitized. This "profound" desensitization occurred after just five days on a junk food diet.
They are not experiencing rewards the way they should," Kenny said. "When you experience that, one way of feeling better is to go back to the junk food."
"They lose control. This is the hallmark of addiction."
In another test of their addiction hypothesis, the researchers used a virus to block the D2 receptors in healthy rats. All those rats soon became compulsive eaters.
Conducte other experiments that showed that even when electorcuted when eating junk food, the addicted rats ignored the discomfort and kept eating.
When the researchers removed the junk food only provideing healthy rat food, the rat volutnarily starved for 2 weeks.
dopamine-junk food connection was actually put forward by former FDA Commissioner David Kessler in his best-selling book, The End of Overeating.
"Food can be highly addictive," said author and nutritional supplement producer Jordan Rubin. "When people describe overeating and weight loss as a battle, this is why."
He called for more research into which individual components of junk food, such as MSG, might be behind its addictive effects.
Obesity researcher Ralph DiLeone of Yale University noted that more research is needed into the long-term effects of such addiction, even if an animal later switches its diet and loses weight.
"They might be a normal weight, but how they respond to food in the future may be permanently altered," he said.
Suggesting yet another area for future research, Kenny has expressed hope that better biochemical understanding of food addiction might someday enable the development of a drug or vaccine as a treatment for compulsive eating.
Further resources
|
You might also be interested in the following:
|
.jpg) |
How We Are Wired for Addiction
Obesity and Food Addiction
Book Review: Molecules of Emotion
Addictions
Depression and Mercury Toxicity
Research: Depression and Mercury Toxicity
For a comprehensive approach to detoxification and diet refer to The Natural Recovery Plan book
|
|
|
Or for all media use the Search facility at the top of the page
|
|
Junk Food is Addictive: Article summary
This article looks at recent human and rat studies that indicate that junk food is highly addictive and that this effect is mediated by the dopamine (D2) receptors in the brain. The actions of dopamine, and the up- and down-regulation of dopamine receptors in response to under- or over-stimulation are examined.
Click the icon for the blog version of this article
|
Click the icon if you would like to republish this article
|
|
|
|
To receive a FREE report and the newsletter fill in your email details in the box on the top left.
The Natural Recovery Plan Newsletter December 2010 Issue 12. Copyright Alison Adams 2010. All rights reserved
Dr Alison Adams Dentist, Naturopath, Author and Online Health Coach www.thenaturalrecoveryplan.com
|
"Great information about mercury, Alison. It is 20 years since I last placed an amalgam in a patient's mouth and NOBODY has ever asked me to put an amalgam filling in instead of the tooth-coloured, metal free alternatives!"
