Salt: New Studies Show Hazards For Brain Function
The latest study to show a link between a high-salt diet and memory and thinking problems was done in mice. But earlier research on humans first suggested a link between high-salt diets and brain disorders as well.
In the newest study, researchers fed mice either 8 or 16 times the normal amount of salt in their diet. Within 8 to 12 weeks, the mice showed signs of memory and thinking problems. They had trouble telling new and familiar objects apart. It got harder for them to get through mazes. And they couldn’t build a nest as well. These behaviors are all central to a mouse’s interaction with the world.
“We translate that in humans to activities of daily living, and that’s what we would call severe cognitive impairment or dementia,” says Costantino Iadecola, MD, a professor of neurology and neuroscience at Weill Cornell Medical College in New York City and the study’s lead researcher.
For humans, impairment caused by excess salt intake would display as having memory problems, disorientation, and not being able to dress, cook, or pay bills. These symptoms are known to mimic Alzheimer’s disease and dementia.
Iadecola says the amount of salt he and his colleagues fed the mice was extreme. It likely would be 5 to 6 times the salt in a typical American diet.
The fact is; no one knows exactly how much salt Americans eat, because most of it is hidden in processed foods. The amount is probably underestimated.
Salt: Potential Game-changer
The study could change the conversation about diet with patients, says Pinky Agarwal, MD, a neurologist who specializes in movement disorders like Parkinson’s disease at EvergreenHealth in Kirkland, WA, and a fellow of the American Academy of Neurology. He says If a patient does not have hypertension, then salt is not discussed.
When doctors think about salt and patient health, they focus mostly on high blood pressure, cardiovascular disease, and stroke.
Salt: Why Do We Need It?
In the Iadecola study, when the mice ate their doctored food, the excess salt triggered a response in their small intestine. It started to produce large amounts of Th17, a type of white blood cell involved with the immune system. This led to a rise in levels of another component of the immune system, a protein called IL-17.
That was a problem for the mice, and it likely would be for humans as well. When the body produces too much IL-17, it can no longer supply enough of a chemical called nitric oxide, which is made by cells lining blood vessels. When nitric oxide levels drop, blood vessels cannot relax, which leads to less blood flow to the brain.
In short, nitric oxide is necessary for smooth brain functioning.
This discovery that salt can lead to memory and thinking problems via reactions in the gut is exciting, says neurologist David Hafler, MD. It demonstrates that diet can be a major influence in vascular dementia
This shows that dietary influences may be a major influence in vascular dementia.
Salt: Are The Effects Permanent?
The answer, happily, is no. Once the mice returned to their normal diet, their brain function returned to normal. That suggests that problems caused by eating too much salt may be reversed once you cut back. And, of course, these problems may be prevented by avoiding a high-salt diet in the first place.
The key question: is there a point at which the brain will begin to suffer permanent damage? The answer, currently, is unknown. But, the results of this study are clear: Use salt in moderation. Watching your salt intake may be an important step to preserve your brain function, memory, and prevent dementia.