One of our favorite food additives has come under yet more fire from the medical profession. Now we find out that studies are saying a diet rich in salt can lead directly to cognitive impairment and early dementia. Yikes.
If we want to remain sharp, maybe it’s finally time to say goodbye to potato chips, nachos, mac ’n’ cheese and all those processed foods we love.
We have long known that salt — too much of it — is bad for us. Studies have shown that too much salt can cause hypertension, leading to physiological problems that could compromise longevity such as high blood pressure, heart issues, stroke, kidney diseases and vascular dementia.
A January 2018 study in Nature Neuroscience conducted at the Cornell Weill Medical School at Cornell University has drawn what doctors and scientists call a “gut-brain” connection, meaning what we ingest, like too much salt, can have a bearing on our mental functioning. At least, it has in mice. Previously, effects of salt on cognitive functioning were attributed to hypertension.
“This is new. It’s the first time a direct connection has been made between the gut and brain and has great potential, but it’s just a first step,” says Dr. Hamid Okhravi, associate professor of medicine/geriatrics at Eastern Virginia Medical School in Norfolk, Va., and director of the Memory Consultation Clinic at EVMS’s Glennan Center for Geriatrics and Gerontology.
In the study, mice were given a high salt diet — from 8 to 16 times greater than their normal intake of salt, which would translate to a very large amount in humans. They showed loss of brain function associated with memory and learning. The study revealed a startling 28 percent drop of blood flow in the cortex and 25 percent in the hippocampus. The mice did poorly on several tests, even solving mazes, a mice specialty.
The villain is a reduction in nitric oxide, which is generated in endothelial cells. It all starts when too much salt is introduced in the diet and our white blood cells go into high gear, producing an increase in IL-17 (Interleukin-17), a protein that suppresses nitric oxide flowing to the brain. The good news is that four weeks after returning to a normal diet, the mice regained normal brain functioning.
Rather than sounding the alarm too loudly, Okhravi issued a word of caution. “While this could be a breakthrough study, results we see in mice do not always translate to humans,” he says. “So, the next step, I think, would be to give healthy human volunteers a high-salt diet for a short period of time and see if it causes a drop in brain blood flow. A big discovery, at least in mice, is that blood pressure does not have to increase for salt to affect brain functioning. Salt may affect the brain with a different mechanism.”
Like Giuseppe Faraco, the first author of the study, Okhravi sees this new information about the connection between salt and the brain being used to combat other diseases — such as multiple sclerosis, rheumatoid arthritis and bowel diseases — by increasing nitric oxide. “But that’s all down the road,” he says.
So what does all this mean for the person in the street — or more to the point, at the dinner table or with a hand buried in a bag of chips watching TV? We probably don’t need to forsake all of our favorite things. At least not just yet.
Almost all of us can cut back on our salt intake. We need sodium for fluid balance and cellular homeostasis. But a 2015 study by the National Health and Nutrition Examination Survey quoted in the Journal of American College of Cardiology states that 90 percent of Americans ingest more sodium than the 2,300 mg recommended by the American Heart Association to maintain good cellular functioning. Almost 70 percent of the sodium in our diet comes from processed foods.
Okhravi suggests incorporating elements of the DASH diet — Dietary Approach to Stop Hypertension — as one way to keep our salt intake in check. The diet emphasizes vegetables, fruits and low-fat dairy products, with moderate amounts of whole grains, fish, poultry and nuts, as well as limited intake of red meat, sweets and fat.
In the meantime, as we await more tests, we would be wise to monitor our chip intake.