Salt Cravings Linked to Addiction, Says New Study

By Dirk Hanson 07/15/11

Scientists studying the ancient appetite for salt believe that drug gratification makes use of the same evolutionary pathway.

Gateway drug?
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An instinct deeply imbedded in the human brain—the craving for sodium—has been the subject of a lot of talk in scientific circles the past few days. This rather mundane subject interested a team of Duke University Medical Center and Australian scientists, who have found that the ancient appetite for salt may have been a biological ancestor of today’s craving for addictive drugs.

Salt appetite has been evolving for more than 100 million years, the researchers argue, in the early online edition of Proceedings of the National Academy of Sciences, while psychoactive drugs and addiction are comparatively recent by comparison. Such drugs “likely reflect usurping of evolutionary ancient systems with high survival value by the gratification of contemporary hedonic indulgences.” In other words, primitive reward systems designed to make sure we don’t starve, or die of malnutrition, or die of thirst, or fail to propagate, have no defense against the artificial reward stimulation provided by alcohol, cigarettes, or heroin. In this theory, drugs of abuse are an evolutionary trick played on a human brain not evolved to cope with such chicanery.

“Though instincts like salt appetite are basically genetic neural programs, they may be substantially changed by learning and cognition," said co-lead author Derek Denton of the University of Melbourne and the Florey Neuroscience Institute. "Once the genetic program is operating, experiences that are part of the execution of the program become embodied in the overall patterns of an individual's behavior, and some scientists have theorized that drug addiction may use nerve pathways of instinct. In this study, we have demonstrated that one classic instinct, the hunger for salt, is providing neural organization that subserves addiction to opiates and cocaine." Deeply embedded pathways in the brain, furrowed by an ancient instinc, may explain why addiction treatment with the chief objective of abstinence is so difficult, said Denton.

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Dirk Hanson, MA, is a freelance science writer and the author of The Chemical Carousel: What Science Tells Us About Beating Addiction. He is also the author of The New Alchemists: Silicon Valley and the Microelectronics Revolution. He has worked as a business and science reporter for numerous magazines and trade publications including Wired, Scientific American, The Dana Foundation and more. He currently edits the Addiction Inbox blog. Email: [email protected]