Even though you can’t call your penchant for junk food an ‘addiction,’ the brain does have a similar pathway for both drugs and salt.
Until now it wasn’t clear which receptors in the brain control salt cravings, although previous research has shown that the opioid system – our reward circuitry – is definitely at play.
Now a team of Aussie scientists have built on over four years of investigations, and found the specific receptor by studying salt-deprived mice. The research was published today in the Proceedings of the National Academy of Science (PNAS).
Blocking the craving
Salt is a trace mineral our bodies need for optimal function. So, just like with food and other pleasant things, we have brain circuitry that rewards us for seeking out salt, explains lead researcher Dr Craig Smith from Deakin University and the Florey Institute of Neuroscience and Mental Health.
The researchers deprived mice of sodium, and then gave them a salty drink and three different opioid blockers. Seeing which blocker worked to stop their salt cravings helped them pinpoint the specific opioid receptors that control the need for salt. Furthermore, the researchers traced the cravings back to an emotion-processing brain region called the central amygdala.
“Essentially, [opioids] are a group of neurotransmitters that have been known for a long time to be involved in reward for when we do things like socialise, have sex or eat food,” says Smith.
He explains that salt cravings work similarly to drug addiction, in that the opiate system originally evolved in animals as a mechanism for controlling salt intake, but can be hijacked by opiate drugs such as heroin and morphine.
However, Dr Zoltan Sarnyai, a neuroscientist and drug addiction expert from James Cook University, emphasises that the study does not talk about 'salt addiction.'
“[The study] is about a principal motivational mechanism in the brain, to obtain enough salt for animals that live far away from oceans where the salt concentration is low,” he tells SBS Science.
Medication against junk food?
Sarnyai says that people who are already eating lots of high-sodium foods are unlikely to be depleted of salt like the mice in the study. However, the findings could potentially lead to future treatments for people who struggle to maintain a low sodium diet.
“As excessive sodium consumption has negative health consequences such as hypertension and cardiac dysfunction, a better understanding of how the brain processes information related to salt appetite might in the future lead to therapeutic interventions,” he tells SBS Science.
Smith says the next step in the research will be to see if the results can be translated into human subjects, making new medications a possibility.
“If you have a drug that makes you crave salt less, that might also mean that you crave junk food less,” he says. “So you’ll be able to, using less willpower… choose healthier food options.
“Another long-term future direction would be to try and determine that therapeutic angle, developing drugs which can result in less salt craving and perhaps promote better dietary choice and habits.”