By Margarita Nahapetyan
Salt is a natural antidepressant and helps people to improve their mood - this way scientists are explaining why Americans tend to consume too much of it.
University of Iowa psychologist Kim Johnson and colleagues, performed series of tests on rats, and found that when the animals are deficient in sodium chloride, common table salt, they experience no pleasure in things they normally enjoy, like drinking a sugary beverage or pressing a bar that stimulates a pleasant sensation in their brains. "Things that normally would be pleasurable for rats did not elicit the same degree of relish, which leads us to believe that a salt deficit and the craving associated with it can induce one of the key symptoms associated with depression," Professor Johnson said.
According to the experts, when a sense of pleasure in generally favorite activities is being lost, this could be one of the most important signs of psychological depression. And, the assumption that salt is a substance that naturally helps to boost mood, could explain why people like to over-ingest it, even though it is a known fact that salt contributes to high blood pressure, heart disease, stroke and other health-related problems. The worldwide average daily salt intake for a person is about 10 grams per day, which is by nearly 5 grams greater than is recommended by the U.S. Food and Drug Administration, and approximately by 8 grams above the amount that is actually needed by human body.
As a food preservative, salt was first discovered around 2000 B.C. It used to be a scarce luxury at that time, and because of its value Roman soldiers were paid in salt. The word salary, that is presently used to describe wages, is derived from the Latin "salarium" for salt. Even after the invention of mechanical refrigeration in the 19th century, that, in turn, lessened the need for salt, the consumption continued to increase because people got used to the taste and it had become relatively cheap. Nowadays, 77 per cent of our salt intake comes from processed and restaurant foods, such as frozen dinners and fast food.
The scientists believe that evolution could have played a significant role in people's cravings for salt. Humans evolved from early creatures that lived in salty oceans, and after moving to a land, the body was still in need for sodium and chloride in order to allow fluids pass in and out of cells and to help nerves transfer information throughout the brain and body.
Another factor, according to experts, that plays an essential role in making sure that there is enough salt in the body, is behavior. Animals, like humans, have a taste system that enables them to detect salt, as well as the brain that fixates the location of salt sources. A pleasure mechanism in the brain is being activated the moment salt is being ingested. In other words, when the body needs salt, it always figures out how and where to find it and conserve it. However, the experts today find more and more evidence showing that salt is a very addictive substance, and compare it even to a drug.
One of the addictive symptoms of salt, the scientists believe, is that people are using it anyway, even being aware of its harmful effects on health. Many individuals are being warned to decrease salt intake due to health-related issues, but they are unable to do so because they like the taste and find foods that are low in sodium too soft and tasteless. Another strong symptom of addiction is the development of intense cravings when drugs are withheld. Investigation and tests by Johnson and colleagues showed that there were similar changes in brain activity of the rats whether they were denied drugs or salt-deficient.
Kim Johnson, who practices psychology and integrative physiology in the College of Liberal Arts and Sciences and pharmacology in the Carver College of Medicine, published the results of the study in the July issue of the journal Physiology & Behavior in collaboration with Michael J. Morris and Elisa S. Na, University of Iowa graduate students.