Can Salt Shake Off the Blues?

The role of salt in human history is long and varied. As they have for thousands of years, camel caravans continue to plod across the Sahara, transporting salt slabs to civilization from mines located in the desert’s interior. Salt has been used as currency and as a food preserver and enhancer. In addition, it contains sodium, which is crucial to maintaining complex functions in the bodies of humans, mammals and some plants. But in recent years, salt has been demonized for its contribution to high blood pressure and heart disease, and people are encouraged to cut way back on consumption. That’s not easy for most, and a fascinating new study offers a hint as to why that may be. Salt, it appears, may be something of an antidepressant.

Scientists from University of Iowa depleted rats’ stores of sodium by giving them a drug that caused the kidneys to flush it out. They also deprived the rats of salt in their diet. Researchers followed up with behavioral tests to see whether there was any change in how the animals reacted toward things they usually enjoyed. There certainly was a change — the rats lost interest in activities that they had previously relished, including pressing a bar that stimulated a pleasure pathway in their brain. The inability to experience pleasure is called anhedonia and it is a well-established symptom of depression. To find out more, I called the study author, Alan Kim Johnson, PhD, who is a professor of psychology at the University of Iowa. Dr. Johnson says his interest in the topic was motivated by a paper published in the mid-1990s that suggested that a group of people who had chronic fatigue and low mood may have had sodium deficiency. The subjects were told not to restrict their salt intake, and most were also given a drug that reduced sodium loss from the kidneys. Once their sodium balance was restored, both problems disappeared. Since Dr. Johnson has long been interested in and done research into how the brain is involved in high blood pressure, this led him to wonder if changes in mood might be a reason people continue to crave salt even though they are told it is bad for them.

Dr. Johnson emphasized that his study does not imply that people should consume salt to combat depression, or that excess amounts of it are healthy. He merely wants people to recognize that salt is much more complex than simply being “bad for you.” How salt contributes to or detracts from health and well-being is not yet fully understood. Dr. Johnson noted that, “It may even be true that, in some cases, low sodium levels can promote hypertension by causing the body to overreact through changes in hormones or nervous system responses.” Although we think of salt depletion as rare, Dr. Johnson notes that it is common among people working or playing sports outside in warm weather or on salt-restricted diets. He suggests that individuals who find themselves beset by low mood should ask their physician whether a recent change of diet or exercise routine might have resulted in decreased levels of sodium in the body. He also agrees it may not be such a bad idea to enjoy a small bag of chips or salted nuts after jogging or tennis on a hot day.