Salt-deprived rats are sad. They loaf around their cages, ignoring the sugar water that usually brings them joy. It’s classic depressed behavior.
I unwittingly ran a similar experiment on myself for the better part of 20 years. I was sweating buckets—unlike pigs, who don’t actually sweat by the way—on the jiu-jitsu mat, but wasn’t consuming enough sodium to replace my losses. I felt low-energy, foggy, and, as I think back, losing passion for my sport. I wasn’t giving my body what it needed, and my mood paid the price. Getting more salt was the remedy.
Compared to other factors, the link between sodium status and mood isn’t well-publicized. I want to change that. I’m not saying salt is a cure for depression, but I do believe it’s worth considering as part of a holistic approach to mood maintenance. Mental health is the fruit of many inputs. And oftentimes many things are out of our control, but getting enough sodium isn’t one of them.
Today, I’ll explore why we crave sodium, how sodium deficiency can affect the brain, why sodium cravings may impair mood, animal and human evidence on salt depletion and depression, and practical advice on sodium intake. Let’s start with a little trip back to the past to learn from our long-lost ancestors.
We Evolved to Crave Salt
The very building blocks of life evolved in the salty sea. And when our earliest ancestors crawled out of it, they didn’t stop needing sodium chloride (salt) to regulate vital bodily functions. Millions of years later, descendants of these ancestors—the early hominids—began roaming the hot plains of Africa. In this sweltering climate, salt was not only hard to find, but it was also rapidly depleted through sweating.
Natural selection pushed our ancestors to develop keener tastes for sodium when they needed it most. Hominids who prized salt flourished, and those who didn’t vanished. Something similar happened with herbivorous mammals. A plant-based diet provides scant sodium, so plant eaters evolved to cherish salty tastes. Think of the cow in salt lick heaven.
I’ll explore the neural and hormonal causes of sodium cravings now. Learning these mechanisms will help us understand how sodium deficiency impairs mood.
Sodium Appetite Can Impact Neural Pathways
Sodium appetite is largely regulated by the renin-angiotensin-aldosterone system. This trio of hormones fires up in response to low blood volume (a sign of sodium depletion) and yells HEY BOZO, eat some sodium! And until you do, I’ll minimize your sodium losses.
Specifically, the system interacts with brain regions to induce thirst and sodium appetite, and to increase sodium reabsorption in the kidneys. For example, two brain areas—area postrema and the nucleus of the solitary tract (which happen to be the names of my pet fish)—are sensitive to the sodium-retention hormones aldosterone and angiotensin II. When you’re low on sodium, your kidneys and adrenal glands take note and release these hormones, activating these brain areas to stimulate a desire for sodium.
Then there’s the nucleus accumbens, a brain region that influences reward and reinforcement. Anything to do with appetite and craving involves this hunk of gray matter, and sodium appetite is no different.
Here’s a further finding that blew my mind. In rats, sodium deficiency changes how the nucleus accumbens operates. The brain region starts to process salty tastes like it processes sugary tastes (as super rewarding!). Researchers call this phenomenon the hedonic shift.
So yes, the brain is a beehive of activity when we need more sodium, literally altering its neural pathways. As you’ll learn, this can be bad news for mental health.
Why Does Sodium Deficiency Alter Mood?
In 1954, Dr. James Old and Dr. Peter Milner designed a clever way to test pleasure-seeking behavior in rats. The experiment is fairly simple and has since been repeated many times. When a rat presses a lever, the action electrically stimulates a brain region linked to pleasure. Unsurprisingly, the rat keeps pressing this lever because it’s rewarding. But when sodium-depleted, rats tend to show disinterest in pleasure levers and sugar water. Why?
One hypothesis is that sodium deficiency makes salty tastes more rewarding at the expense of other pleasures. This makes sense from an evolutionary lens. Sodium is an essential nutrient—and prioritizing an essential nutrient over nonessential activities will increase the chance of survival. Specifically, a brain region called the rostromedial tegmental nucleus may tamp down enjoyment for other behaviors we might normally find pleasurable, like reading, skiing, or compulsively gulping sugar water. Meanwhile, the nucleus accumbens ramps up enjoyment of salty tastes via the hedonic shift. In other words, salt makes you happy when you’re sodium-depleted, but little else will.
Cortisol, the get-up-and-go stress hormone, may also be involved. When someone suffers from a sodium imbalance, their cortisol levels go WAY up. High cortisol, in turn, may drive depression, fatigue, and stress.
The final hypothesis suggests that the salt cravings—not the deficiency itself—may underpin symptoms of depression. How did researchers test this? They made sodium-sufficient rats crave sodium anyway by administering an aldosterone precursor. What they found is that the rats—who craved sodium despite having no deficiency—stopped pursuing pleasure. Their perceived need for sodium made other rewards pale by comparison. Practically speaking though, this may be a moot point because craving and deficiency typically go hand-in-hand.
Human Evidence That Sodium Deficiency Impairs Mood
Most research linking sodium deficits to mood issues has been conducted on animals. However, data suggests that humans experience similar effects as our furry friends:
- In 2020, researchers found a significant link between low serum sodium and depression symptoms in 200 patients on dialysis.
- In 2005, researchers found higher levels of aldosterone in 65 clinically depressed patients vs. 65 age-matched controls. One cause of overproduction of aldosterone is hypovolemia (low blood volume) which can result from a lack of water or sodium.
- In 2001, The British Journal of Psychiatry published a community survey of 340 older adults correlating hypotension (low blood pressure) with less positive moods. Of course hypotension is a complex and multifactorial issue, but one of those potential factors is low blood volume which can be caused by inadequate fluid and sodium intake.
I’ll also mention the anecdotal evidence, not only from my past, but from many reports of folks following my work. The theme is clear: Sodium-deficient people feel MUCH better after bumping up their salt intake with LMNT or the salt shaker. Higher energy, fewer cramps, and better moods are more often the rule than the exception. Experiment yourself and listen to your body—you’ll feel the difference when you get it right.
Recap and Practical Thoughts
Here’s a quick refresher on what we covered today:
- Sodium scarcity pushed animals to crave salt via natural selection.
- Salt depletion makes rats (and that Robb Wolf guy) sad.
- Sodium deficiency instructs the dopamine system to make sodium more rewarding.
- When someone is sodium deficient, other typically pleasurable things become less rewarding.
- Salt-depleted humans often feel better after increasing their sodium intake.
The practical takeaway is to get enough sodium to support your body. Generally, I recommend 4–6 grams of sodium per day as a baseline for healthy folks. And if you’re quite active, you may need much more to replace what you lose via sweat. If you’re keen on exercise, you can learn how to be precise about your sodium intake by reading my articles on sweat rate and sweat sodium concentration.
I hope this article taught you something new and interesting! Stay Salty.