In the U.S., an estimated 3.2 million adolescents between the ages of 12 and 17 suffer from depression, defined as having at least one major depressive episode in a year. This accounts for 13.3% of adolescents, who experience a period of at least two weeks with a depressed mood, loss of interest in daily activities and other symptoms, such as problems with sleep, appetite, energy, concentration or feelings of self-worth.1
Depression among adolescents is on the rise, increasing by 30% in the last 10 years.2 Many factors may be to blame, but one that continues to fly under the radar is diet, particularly an unhealthy one based on processed foods and fast foods.
Junk Food Diet Linked to Depression in Teens
Researchers at the University of Alabama at Birmingham looked into the role two dietary factors play in symptoms of depression among adolescents, in this case African-American teens who may be at an increased risk of both unhealthy diet and depression.
They analyzed the excretion of sodium and potassium in the urine of 84 urban, low?income adolescents. Higher levels of sodium in the urine can be an indication of a diet high in sodium, such as processed foods and salty snacks. A low level of potassium, meanwhile, is indicative of a diet lacking in fruits, vegetables and other healthy potassium-rich foods.
As might be expected, higher sodium and lower potassium excretion rates were associated with more frequent symptoms of depression at follow up 1.5 years later. “This study was the first to demonstrate relationships between objective indicators of unhealthy diet and subsequent changes in depressive symptoms in youth,” the study noted.3
It’s possible that eating foods high in sodium and low in potassium may lead to depression by negatively influencing neurotransmitters and neural function during a time that is particularly vulnerable.
“Given the substantial brain development that occurs during adolescence, individuals in this developmental period may be particularly vulnerable to the effects of diet on the neural mechanisms underlying emotion regulation and depression,” the researchers wrote. In addition, poor diet could influence depression by disturbing the gut microbiome, which could further influence brain function.4
Past studies have also confirmed the diet-depression link among children and teens. When researchers systematically reviewed 12 studies involving children and adolescents, an association was revealed between unhealthy diet and poorer mental health, as well as between a good-quality diet and better mental health.5
The consumption of junk food has also been associated with psychiatric distress and violent behaviors in children and adolescents, which includes worry, depression, confusion, insomnia, anxiety, aggression and worthless feelings, as well as physical fighting, being a victim and bullying.6
Unhealthy Diet Linked to Depression in Adults, Too
While teens may be especially vulnerable to the negative effects of a poor diet, adults, too, may suffer mentally from a diet based on unhealthy foods. An inflammatory diet, which can include one high in processed foods, was associated with recurrence of depressive symptoms in women, for starters.7
Likewise, in 2018, a systematic review and meta-analysis with a total of 101,950 participants also found an association between a pro-inflammatory diet and risk of depression.8 People who ate a pro-inflammatory diet were 1.4 times more likely to suffer from depression.9 “Thus, adopting an anti-inflammatory diet may be an effective intervention or preventative means of reducing depression risk and symptoms,” according to the study.10
Sugar intake, a known inflammatory food, is also specifically linked to common mental disorder and depression. Research published in 2002 also found a “highly significant correlation between sugar consumption and the annual rate of depression.”11
Men consuming more than 67 grams of sugar per day were 23% more likely to develop depression over the course of five years than those whose sugar consumption was less than 39.5 grams per day.12 Several potential mechanisms were discussed for why a high-sugar diet may influence depression risk, including:13
Sugar may decrease levels of brain derived neurotrophic factor (BDNF), leading to hippocampal atrophy in depression
Consuming sugar may increase circulating inflammatory markers, which could lead to depressed mood
A high-sugar diet may cause an exaggerated insulin response, influencing hormone levels and mood
Sugar has addiction-like effects, which could influence dopamine and mood
A high-sugar diet may lead to obesity, which could contribute to depression via inflammatory pathways as well as psychosocial factors
Eating Real Food Is Key for Good Mental Health
You can improve your mood and your mental health by tweaking your diet for the better. Researchers even compiled a list of five key dietary recommendations for the prevention of depression, based on current published evidence. The basic premise is to eat real food. The five strategies include:14
Follow “traditional” dietary patterns
Increase consumption of fruits, vegetables, nuts and seeds
Eat lots of foods rich in omega-3 fats
Replace unhealthy foods with wholesome nutritious foods
Limit your intake of processed foods, fast foods, commercial bakery goods and sweets
That last one is truly essential, in part because of the additives in processed foods, such as emulsifiers. Previous research has shown that adding the food emulsifiers CMC and P80 to the diet leads to low-grade inflammation, obesity and metabolic abnormalities in mice, while disturbing gut microbiota.15
Because your gut and brain communicate via your gut-brain axis, altering microbes in your gut can influence anxiety and behavior, leading researchers to speculate that consuming emulsifiers may also influence mental health and behavior.
Likewise, in 2015, it was previously found that low concentrations of emulsifiers (CMC and P80) induced low-grade inflammation, obesity and metabolic syndrome in mice.16 “Depression and inflammation fuel one another,” researchers wrote in the American Journal of Psychiatry, adding that in the case of inflammation, “depression fans the flames and feasts on the heat.”17
Making sure you’re getting enough anti-inflammatory omega-3s in your diet, either from wild Alaskan salmon, sardines, herring, mackerel and anchovies or a high-quality animal-based omega-3 supplement, is also crucial for optimal mental health. B vitamins are also important, and low levels of B vitamins are common in patients with depression, while vitamin B supplements have been shown to improve symptoms.18
Further, in a study of 9,700 vegetarian (including a small number of vegan) men, vegetarians were more likely to suffer from depression than meat eaters, even after adjusting for variables like job status, family history and number of children.19 Vegetarians tend to have lower intakes of omega-3 fats, vitamin B12 and folate, which could affect depression risk.
In the case of folate, it helps your body produce mood-regulating neurotransmitters, including serotonin and dopamine. One 2012 study found people who consumed the most folate had a lower risk of depression than those who ate the least.20 Addressing nutrient deficiencies, as well as optimizing your diet, are keys to mental health and should be first-line strategies to treating depression.
How to Get Teens to Eat Better
It’s clear that your mental health depends, at least in part, on what you eat. Less clear is how to get teenagers — a population keen on junk food — to eat better. One simple tip? Let teenagers know they’re being manipulated by food marketers.21 Students who read an exposé that revealed the manipulative practices used by marketing companies chose to eat less junk food and drank more water instead of soda.
Students who read about the junk food industry’s manipulation also chose healthier foods for the remainder of the school year — a period of about three months. Tapping into teens’ natural desire to rebel against authority proved to be an effective way to prompt significant changes in dietary choices.
Teaching children to eat right from a young age can alter their health significantly, even beyond mood and depression. In one study, eating fast food three or more times per week was associated with an increased risk of severe asthma, rhinitis and eczema.22
Children who eat more fast food also progress slower academically, with test score gains about 20 percent lower in children who ate the most fast food compared to those who ate none.23 One British study also revealed that kids who ate a predominantly processed food diet at age 3 had lower IQ scores at age 8.5.24
Junk Food Marketing Targets Youth
Yet, children are exposed to junk food marketing 27.3 times a day, at home, in public spaces and even at school. Marketing for sugary drinks, fast food, candy and snack foods were the types most commonly encountered by the children in one study.25
With the continual barrage of marketing and junk food’s highly addictive nature, it’s easy for teens to fall into a trap of unhealthy eating. As a result, even the World Health Organization is calling for more protections for children from the harmful effects of junk food and junk food marketing:26
“Food advertising and other forms of marketing have been shown to influence children’s food preferences, purchasing behaviour and overall dietary behaviour. Marketing has also been associated with an increased risk of overweight and obesity in children.
The habits children develop early in life may encourage them to adopt unhealthy dietary practices which persist into adulthood, increasing the likelihood of overweight, obesity and associated health problems such as diabetes and cardiovascular diseases.”
Depression, unfortunately, can also be added to those health problems, so in addition to modeling healthy eating behaviors for your teen by eating right yourself, have a serious conversation about the profit-driven motives behind junk food ads. It just may prompt your teen to rebel in a good way and choose healthier, real foods instead of processed junk.
Finally, if you think your teenager is suffering from depression, keep a close watch for signs they may be contemplating suicide. If there are any doubts, please call the National Suicide Prevention Lifeline, a toll-free number: 1-800-273-TALK (8255), or call 911 or take your teen to your nearest hospital emergency department for help.