- Teens with unhealthy eating habits may be more likely to have depression, according to new research.
- A high- sodium, low-potassium diet (such as one with a lot of fast food and not much produce) was linked to more severe symptoms of depression.
- These results suggest eating more fruits, vegetables, and whole grains could help improve mental health. But more research is needed to address other diet and lifestyle factors, as the study doesn’t prove cause and effect.
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New research has found a diet high in sodium and low in potassium, like one with lots of fast food and few fresh fruits and vegetables, may be linked to more severe symptoms of depression in teens.
For the study, published August 23 in the journal Physiological Reports, researchers looked at 76 middle-school students in urban Alabama. They compared self-reported depression symptoms with the teen’s sodium and potassium levels, measured by a urine test, over the course of a year and a half.
Researchers at the University of Alabama at Birmingham found that teens with higher levels of sodium and lower levels of potassium were more likely to report frequent symptoms of depression, even after adjusting for other factors like age, baseline depression levels, and body mass index.
They also found that sodium seemed to have a cumulative effect on mood over time: Depressed teens with a high sodium intake weren’t necessarily depressed at the beginning of the study.
The findings suggest a diet high in salt and low in potassium could be harmful to mental health over time, and eating more fruits, vegetables and other whole foods might help mitigate depression symptoms.
Researchers were careful to note that the study included mostly low-income, African-American teens, a group already at greater risk of both poor diet and depression, according to sociological research.
The data was part of a larger study on how teens in disadvanataged communities respond to violence, explained Sylvie Mrug, lead author of the study and chair of the psychology department at UAB. The researcher had taken urine samples to test for stress hormones, but the tests also proved to be a strikingly accurate assessment of sodium and potassium in the teens’ diets, Mrug told Insider.
Participants’ family income levels ranged from less than $5,000 to more than $70,000 annually. Researchers didn’t find a connection between family wealth and either depression or sodium intake, suggesting that teens of different background could face the same risks in their diets.
This study adds to growing evidence that food can influence mental health
Poor diet has long been associated with risks of mental health issues, according to the study’s authors, although it’s not clear how.
“This study confirms what we already know, which is processed foods are bad for the brain and for mental health,” said Dr. Drew Ramsey, assistant clinical professor of psychiatry at Columbia University who was not involved in the study.
But while previous research has relied on participants’ self-reported eating habits, a method which has been found to be biased, this study more accurately assessed people’s diets by comparing sodium and potassium levels in participants’ urine.
They found that high sodium and low potassium often went hand in hand, suggesting that teens who eat a lot of salty foods, like chips and other snacks, also tend to eat fewer healthy foods like fruits and veggies. And, when teens did have both high sodium and low potassium intakes, they were most likely to report depression symptoms, researchers found.
Teen girls seemed to be most vulnerable to the impact of diet on their mental health — the connection between sodium and potassium levels and depression was stronger for girls than for boys. And previous research has shown that teen girls tend to be more at risk of depression overall.
“That makes sense because we know around age 13 to 15 is when girls start to experience more depression symptoms compared to boys,” Mrug said. “That difference in symptoms continues through adulthood.”
Researchers have a few theories on how sodium and potassium levels impact the brain. It might influence the production of neurotransmitters, such as the stress hormone cortisol. It could also interact with the gut microbiome, the colony of healthy bacteria that live in our stomach and are linked to a growing number of health factors, from improving sleep to curing cancer.
But it is clear the teenagers are more vulnerable than adults to side effects of a bad diet, since their brains are still developing.
This research is a promising sign that shifting to healthier eating habits in youth could lead to better mental health over time.
“Nutritional psychiatry is a way to engage with people about their mental health using food and nutrition as a starting point,” Ramsey said. “Research like this is encouraging because it tells us we have a piece of mental health at the end of our forks. It’s not a panacea, but it can make a difference.”
However, these results will need to be repeated with sample size larger than 76 people, the researchers noted. And more dietary factors, like sugar intake, need to be studied to fully understand how food and mood are related.
Mrug said her team is currently working on a new three-year study of middle school students to compare diet with emotional, behavioral, and academic outcomes.