High levels of sodium and low levels of potassium in foods normally found in unhealthy fast food restaurants might have something to do with teenage depression in the United States.

A new study from the University of Alabama at Birmingham (UAB) finds that one culprit in rising depression among U.S. teens might be a high fast-food, low plant-based diet. This basically means a high salt and low potassium intake.

UAB researchers analyzed urine from a group of middle schoolers and found high levels of sodium and low levels of potassium. They also observed signs of depression in this group, as well as in the parents of these kids. The participants consisted of 84 middle school girls and boys, 95 percent African-American from low-income homes.

Researchers tested this same group 1-1 1/2 years later again and noticed more signs of depression. They conclude a high sodium indicates a diet of processed foods and unhealthy snacks.

"High sodium, you've got to think of highly processed food," Sylvie Mrug, lead author and chair of the UAB psychology department, said. "This includes fast food, frozen meals and unhealthy snacks."

Mrug said low potassium is an indication of a diet bereft of healthy fruits and vegetables rich in potassium. These include bananas, sweet potatoes, spinach, tomatoes, oranges, avocados, yogurt and salmon.

The study also found higher urine levels of sodium and potassium at baseline predicted more signs of depression a year and a half later. This finding held true even after adjusting for variables such as blood pressure, weight, age and sex.

"The study findings make sense, as potassium-rich foods are healthy foods," according to dietitian Lisa Drayer, a CNN health and nutrition contributor.

"So, if adolescents include more potassium-rich foods in their diet, they will likely have more energy and feel better overall -- which can lead to a better sense of well-being and improved mental health."

UAB researchers only found an association between sodium and depression, and not a cause and effect, which means much more research on this needs to be done. But the UAB study will provide a valuable jumping-off point for future studies, especially since this study confirms that a high fast-food, low plant-based diet might be linked to depression, which is rising at frightening rates among teens.

Fast Food
Consuming too much salt increases water retention and raises the risk of hypertension over time. Photo by Gilly on Unsplash

Depression among middle school children is on the rise in the U.S. Federal government data revealed the rate of major depressive episodes among children 12 to 17 years old within the last year had skyrocketed by a massive 52 percent between 2005 and 2017.

Among older teens and young adults, the rate of depression, psychological distress and suicidal thoughts over the last year was even higher - 63 percent.

Researchers, however, admit other factors also contribute to the deadly depression trend among teens. Among these factors are overusing and misusing social media and a chronic lack of sleep.

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