Rock, sea, Himalayan pink — salt is the most central ingredient in our kitchens. A savory meal without the white stuff is unthinkable. And not even chocolate is safe because good chefs know that sweet with a dash of salt brings out the flavor that much more.
Yes, food tastes better when sprinkled with salt, the magic crystalline mineral. It’s hardly surprising, given that it is one of the five basic human tastes: sweet, salty, bitter, sour, and umami. And yet, the magic stuff that titillates our taste buds is also frequently referred to as a “silent killer”. A major contributor to hypertension, salt is linked to 2.3 million deaths worldwide.
The World Health Organization recommends that people not consume more than 5 grams of salt per day. To put that into context, a 200-gram tub of Pringles Salt & Vinegar has 4.6 grams of salt. Bad news for those who love to snack. And as if high blood pressure wasn’t bad enough, new research reveals that eating too much salt could also cause dementia.
So what makes salt unhealthy?
It’s the sodium contained in salt that’s harmful in excess. Standard table salt is approximately 60% chloride and 40% sodium. The human body needs sodium for healthy nerve function and muscle action. But too much sodium causes our bodies to retain more fluids. Consequently, blood volume increases and this creates pressure on the blood vessels. In other words, too much salt can effectively raise blood pressure.
Hypertension (the medical term for ongoing high blood pressure) is a major risk for stroke, heart conditions, and kidney disease. One study found that people who ate a lot of sodium, but not much potassium, had a 20% increased risk of death. Salt is called a “silent killer” because many people with hypertension don’t even realize that their blood pressure is consistently too high.
New research published in Nature warns that perhaps excess salt isn’t only bad for the heart, it could also lead to dementia. Scientists at Weill Cornell Medicine, Cornell University, found that mice fed high-sodium diets had difficulties performing memory tasks. When researchers examined the brain tissue of the mice, they noticed that tangles of a protein called ‘tau’ had accrued.
Accumulation of the defective form of tau is one of the hallmark signs of Alzheimer’s disease in humans. Tau proteins are important stabilizing molecules inside neurons, but chemical changes can damage them. When that happens, they clump together and form tangles inside neurons. Like a blocked pipe, this disturbs the signal transfer between synapses and the affected brain regions can’t function properly.
But how exactly did excess sodium cause cognitive decline in these mice? In 2018, Dr. Giuseppe Faraco, an assistant professor of neuroscience at the Feil Family Brain and Mind Research Institute at Weill Cornell Medicine, proposed that too much salt caused dementia in rodents because it restricted blood flow to the brain. Faraco noticed that sodium decreased nitric oxide levels in the brain — a compound that relaxes and widens blood vessels for blood to flow through more easily.
But Faraco and his team felt there was more to it. In the recently published follow-up study, they discovered that the drop in nitric oxide levels destabilized tau. The protein essentially comes off the cell wall and is then free to accumulate. It’s the nitric oxide that keeps the protein levels balanced. “This demonstrated that’s what’s really causing the dementia was tau and not lack of blood flow. […] There’s more than one way that the blood vessels keep the brain healthy,” said study co-author Dr. Costantino Iadecola, director of the Feil Family Brain and Mind Research Institute at Cornell.
Although the study used mice and the findings are yet to be verified in humans, the team’s message is clear: we should absolutely monitor how much salt we eat. Iadecola warns that “the stuff that is bad for us doesn’t come from a saltshaker, it comes from processed food and restaurant food. We’ve got to keep salt in check. It can alter the blood vessels of the brain and do so in a vicious way.”
What Iadecola may be referring to is recent evidence showing that 71% of the sodium Americans eat comes from foods prepared outside of their homes, such as processed foods or restaurant dishes. Only 5% to 6% of the sodium we eat comes from the saltshaker on our table or the salt we cook with. Salt is a powerful ingredient in many processed foods. Take Cheez-Its, for example. When food scientist John Kepplinger removed the salt in the popular cheese crackers made by Kellogg’s, something peculiar happened: the crackers lost their bright color, they took on a sticky texture, and they began to taste bland. Salt is the secret ingredient to many of your favorite food products.
So, how do you know whether there’s too much sodium in the meals you eat each day? Keeping a food diary and calculating the sodium content, even just for one week, can give you some clues as to where you may need to make cuts. But let’s face it: sodium diaries are impractical for most of us. Instead, you can check the label of processed foods for “sodium” or “Na” and cut down on products that exceed the daily recommended maximum of 5g. If you’re ordering food at a restaurant, ask for a salt-free meal. That way, you’re in control and can season it yourself with a little table salt. Ultimately, cooking for yourself using plenty of fresh ingredients is still your best option to keep salt intake down to a tablespoon a day. Bon appétit!