National Geographic News
Tourists on a salt flat in Chile.

People explore the salt flats of Chile's Atacama Desert.

Photograph by Melissa Farlow, National Geographic

Brian Handwerk

for National Geographic News

Published July 19, 2011

Drugs such as heroin and cocaine may owe some of their addictive powers to an ancient instinct—our appetite for salt.

In a new study of mouse brains, scientists show that the patterns of gene regulation stimulated by salt cravings are the same gene patterns regulated by drug addiction.

Salt appetite is a craving millions of years in the making, with likely roots in the salty seas where life on Earth began. (Related: "Is Salt Nature's Antidepressant?")

"Land dwellers face a problem in that sodium is a trace element, so they have to have a strategy to ingest sodium, and salt craving or sodium appetite is evolution's answer to that," said study co-author Wolfgang Liedtke, an assistant professor of medicine and neurobiology at Duke University.

Salt appetite can be so strong that animals short on sodium will put life and limb at risk to satisfy the hunger. Mountain goats, for instance, are known to cling to sheer cliffs to access a salt lick, even when a misstep means certain death. (Related pictures: "Goats Scale Dam in Italy.")

The new finding suggests that drug addictions may be so hard to overcome in part because cocaine and opiates—both derived from plants—exploit the brain mechanisms critical for salt appetite.

"Cocaine can usurp the ancient [neural] systems that have made animals better survivors," Liedtke said.

The research offers some of the first evidence for addiction processes previously theorized by other experts, added study co-author Derek Denton of the University of Melbourne and the Florey Neuroscience Institute.

Salt Cravings Lead to Rapid Brain Change

Denton, Liedtke, and colleagues used several techniques to figure out which genes in mammal brains were activated by salt cravings, such as withholding salt from test mice or increasing their salt needs by giving them the stress hormone ACTH.

The team noticed that, almost as soon as the salt-depleted mice started drinking salt water, the patterns of gene regulation triggered by the need began to reverse.

The rapid response is a surprise, because it means brain changes in the mice occurred before significant amounts of salt had moved from the stomach to the bloodstream.

"It was stunning and perplexing to see that just ten minutes of drinking salty water led to a complete change of the whole sophisticated and elaborate genetic program," Duke's Liedtke said.

(Related: "Cocaine, Spices, Hormones Found in Drinking Water.")

Addiction Drivers Still Unknown

It's possible that the research may lead to new treatments for drug addiction that don't rely on "cold turkey" abstinence, which is less likely to be successful against such strong, instinctual cravings.

Overall, though, Liedtke cautions that the new study doesn't fully explain the neural drivers of drug addiction.

"Sodium appetite is a healthy instinct. Heroin addiction is a disease that can kill a human," he said. "To go from a healthy instinct to a malady, other things must be happening in the brain."

The salt-appetite research was published online in the early edition of the Proceedings of the National Academy of Sciences.

3 comments
M. Oliveira
M. Oliveira

Hi , did my first note go threw. my ipad crashed on me in the middle of writing im so mad. :-!!!!    P.S. i see this is wrote in Sept. 2013 . i hope everything is still going good for you. i wish you the best. :-) 

Jack Raush
Jack Raush

I do believe that us drug addicts(myself included) have found them selves putting them in the direst situations just to score. And even though we know that this life is not safe, we continually force ourselves into situations which put us at some of the highest risks, so when we try to quit we find our selves so out of balance that our cravings overcome us and put us at risk again, but we don't care and go try again. Personally, after years of addiction to opiates, meth, crack, IV coke, etc etc. I am a garbage can as they would call it but my main drugs of choice were the ones listed above. So when I went cold turkey I was having seizures(from my benzo addiction to klonopin) and terrible effects from quitting to the point that my health was failing, even though when I was using my health was perfect. After 8 months cold turkey I was dying. literally, my teeth were getting cavities which they never had before even through my meth addiction, my heart rate was incredibly out of wack to the tune of 180/115,  but all counselors and doctors refused to write prescriptions that actually did anything for me as my tolerance to all drugs is extremely high and Im a drug addict, so in their eyes I don't need any drugs. Anyway I decided to put myself on methadone after the worst 8 months of my life and as soon as I did, I was feeling better, I'd found the salt lick, or at least part of it, but this time it wasn't at the top of a cliff, it was in the safest environment you can think of, medical supervision, but after a few months, my psychiatric symptoms started coming back, the depession the anxiety, the pain, so I decided to go to a doctor, that most would call shady because he prescribes addictive drugs to addicts but he does it safely and is forerunning a new idea, giving addicts what they want and need. So now I'm on lamictal for mood stabilization, adderall for meth cravings and ADD, Klonopin or generalized anxiety disorder, xanax for panic attacks, and methadone for cravings, pain anxiety, and sleep. 90% of doctors would never prescribe these drugs to a drug addict, but since I'm under constant surveilance through urine testing, counseling, meetings, and GCMS testing to show the levels of drugs in my system, plus my morning drugs are dispensed through my methadone clinic and they give me small takehomes to the order of 2-3 pills, of the addictive drugs for the afternoon doses. This SAVED MY LIFE. I'm no longer looking for the salt lick, as its come to me in the form of legal prescriptions, and its no longer dangerous it is supervised. And this is something we should start to understand as so many drug addicts suffer from mental issues and chemistry imbalances, making them self medicate and self medicate poorly as the drugs aren't pure and its not supervised. I am one of the lucky ones that was given this chance to medicate myself properly with what I need to balance myself and although most people would find this disgusting that you give a drug addict addictive drugs it is what they need in many cases to make them feel normal, happy, calm, so that they can focus on fixing their lives instead of thinking about that salt lick, going crazy, until they relapse. What do you think about my plan? Do you think its dangerous, stupid, a new way to help the addicted? Please lets start a discussion on the pros and cons of replacement therapy as I think more people need to know how it works and why it helps so much better than treatment, and abstinence alone.

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