Study shows that too much salt may cause cognitive impairment
Dear Doctor: I love salty foods, always have, and I don’t have high blood pressure or heart disease or anything like that. But I did see a story recently that said high-salt diets can affect the brain. How worried should I be?
Dear Reader: Our attraction to salt – researchers refer to it as “sodium appetite” – has long fascinated everyone from scientists to philosophers to poets. At a physiological level, our bodies require sodium, which plays a key role in fluid balance, and in nerve and muscle function. As cooks (and eaters) know, adding salt to almost any food makes it taste better. And scientists in Australia recently identified specific pathways in the brain’s emotional center, which light up when salt is consumed, a reward system of sorts.
Yet as your question acknowledges, and as research has shown, too much salt in the diet puts you at risk of high blood pressure and heart disease. Now, a recent study from Weill Cornell Medical College, the research unit and medical school of Cornell University, has added the potential for cognitive impairment to woes caused by too much dietary salt.
When scientists fed mice a high-salt diet, the flow of blood to their brains declined, and the vessels that carried that blood were adversely affected. The mice also began to perform poorly on cognitive tests that, before this change to their diets, they had aced. What was particularly interesting was that, rather than this decline arising from a spike in blood pressure, it appeared to be tied to chemical changes in the brain that were prompted by an immune response in the gut. When the mice were returned to a normal diet, they regained the cognitive ground that they had lost. Whether this same scenario will translate to humans is not yet clear.
As for your own sodium consumption, we believe that even absent physical symptoms like high blood pressure, overdoing it with salt is not a good idea. And if you don’t really know how much salt you’re eating, then you’re like the majority of Americans. That may be why, according to the American Heart Association, most adults consume more than 3,400 milligrams of sodium per day, which is 30 percent more than the organization’s recommended maximum of 2,300 milligrams per day. A whopping 70 percent of that sodium comes from prepared and packaged foods and from restaurant meals. The rest comes out of the salt shaker.
We think it would be wise for you to begin to keep track of your daily sodium intake. Packaged and processed foods will have the numbers you need on their nutritional labels. To be accurate, be sure to pay attention to serving size as well. As of May 7, restaurants with 20 or more locations have been required by the Food and Drug Administration to provide customers with a range of nutritional information, including calorie counts and sodium content. And if you’re a home cook, track the sodium levels – both in the ingredients you’re using as well as the salt you’re adding. Your body and maybe even your brain will thank you.
Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health.
Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.