Let's assume that you've just had your tonsils removed, or that you hurt your back and have been prescribed opiate medications such as hydrocodone or oxycodone to treat the pain. Or perhaps your child has been prescribed Adderall for the treatment of ADHD. What if I told you that following the Centers for Disease Control and Prevention's low-salt guidelines—that is, consuming less than one teaspoon of salt per day, a recommendation that they put forth to basically all healthy Americans—could be placing you or your loved ones at risk of becoming addicted to these medications? Or what if this low-salt advice was predisposing you to sugar addiction? What if you were deficient in salt even if you weren't consciously restricting your sodium?
We all love salt. Just a pinch can make almost any food savory and delicious. But sometimes salt can taste even better than usual, even more rewarding. This occurs when we become salt depleted (also known as salt deficient). If your daily habits include drinking three cups or more of coffee, working out for an hour, or taking medications that are diuretics (including many blood pressure meds), then you could be in a state of salt deficit, even if you don't limit your salt intake. And if you're one of the 25 percent of Americans who has been advised to follow a low-salt diet, whether because of high blood pressure or kidney disease, then you are very possibly in a state of deficit.
Very simply, salt depletion enhances our liking for salt. Without this enhanced liking, we might not ever seek it out and eat more of it during times of need. But a salt deficit might not merely sensitize the brain to the effects of salt; it also sensitizes the brain to other substances, such as certain drugs (cocaine), and medications (amphetamines, such as Adderall, and opiates, such as morphine). Even refined sugar may now be even more rewarding, and thus more addictive.
There is good evidence to back up this idea: Sodium balance is an evolutionary adaptation that is tightly regulated for sustaining life for all vertebrates. Because of this, sodium depletion stimulates an increased salt "appetite" in which animals and humans will seek out salt and consume more of it. This behavior (seeking-out and bingeing) resembles that which occurs in those who are addicted to drugs of abuse. An enhanced reward from salt during salt depletion is a survival mechanism that may now be working against us, as the changes that occur in the brain during sodium depletion mimic that of repeated drug use.
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The myth that salt is addictive, and that the more you eat the higher your tolerance, doesn't reflect the historical data on salt consumption. Indeed, we used to consume up to ten times as much salt as we do today. Our ancestors consumed so much more salt than contemporary humans because it was their main method of food preservation. (Now that the fridge has replaced salt as the main food preservative, we consume much less sodium than we used to.)
What's remarkable is that when a population has free access to salt—when its consumption isn't impacted by either by scarcity, conscious restriction, or on the flip side, use as a preservative—intake consistently lands at three to five grams of sodium per day. It doesn't rise above that level, suggesting that our tolerance or cravings for salt do not go up the more we eat. This suggests that our bodies, not an addiction, control our salt intake. And for the last 8,000 years, we have been consuming a diet higher in salt than we do today.
Furthermore, data shows that salt depletion sensitizes the dopamine system, which is implicated in drug cravings. Sodium depletion has been found to cross-sensitize with amphetamine (a drug known to cross-sensitize with cocaine. Cross-sensitization is a phenomenon that occurs between drugs of abuse, where the use of one drug leads to enhanced effects (and increased abuse potential) of the other. But in this case, sodium depletion, rather than a drug of abuse, is increasing the reward and abuse potential.
Periods of enhanced salt liking only last until the depletion has been corrected, and once corrected, inhibitory signals will turn off the "liking" and turn on the "aversion" signal. This is what I like to refer to as our "salt thermostat," the system by which our body controls our salt intake to ensure optimal health and survival. It seems that the low-salt guidelines could be 'priming' or 'sensitizing' our brains for an excessive reward from refined sugar and drugs of abuse.
Almost 30,000 people die in the United States every year from overdosing on prescription opioids, cocaine, and heroin (this number is rising at an alarming rate). If there is a possibility that some of these overdose deaths could be linked to the low-salt guidelines, it may be time to revisit this advice. Salt deficit is also fairly common. In those with chronic kidney disease (affecting an estimated 31 million people in the United States), the prevalence of low blood levels of sodium is as high as 30 percent. And around 3 to 6 million people in the United States are diagnosed with [hyponatremia](http://www.elseviercme.com/sites/elseviercme.com/files/users/4/910544 hyponatremia article722_14.pdf), or low sodium levels in the blood, every year. Hyponatremia is also very common in those with heart failure and in the elderly.
Sodium depletion early in life (e.g., in utero or shortly after birth) from a pregnant mother adhering to low-salt advice can also predispose children to become addicted to sugar and drugs of abuse. Indeed, salt depletion during these susceptible times seems to chronically activate the salt-liking reward system. While more research is needed to advance this idea, this is just another reason why we should be skeptical of the advice to consciously restrict our salt intake—other reasons including the dubious connection between salt and blood pressure levels, the impact of sodium restriction on weight, among others.
The low-salt guidelines, which began in 1977 with the release of the first US dietary goals, should not supersede salt appetite, which developed over 100 million years of evolution. When it comes to salt intake, our body and brain probably know best. Eating the level of salt that our body drives us to consume, rather than trying to consciously restrict our salt intake (as the low-salt guidelines would have us do) will help ensure that we avoid salt deficit. And if you suspect you may be low in salt because of overtraining at the gym, your insatiable coffee habit, or use of medications, see a doctor. Otherwise, take these guidelines with—well, you know.
James DiNicolantonio is a cardiovascular research scientist at the Saint Luke's Mid America Heart Institute. Parts of this story were excerpted from his new book The Salt Fix, out now. Read This Next: There's No Proof Epsom Salt Baths Actually Do Anything