Sunday marks the end of daylight saving time (DST), a ritual paired with setting clocks back an hour. Debate over whether we should kill DST aside, what it immediately means is less after-work daylight. Evening light fades sooner. In New York City, where I live, the Sun sets before 5 p.m. in November.
For some, this increased darkness is a challenge for mental health. Seasonal affective disorder (SAD) is a type of depression characterized by the change in seasons — this means symptoms can last for about four to five months per year. While some people experience it in summer, it’s most often associated with winter. Scientists don’t completely understand what causes SAD, but it’s theorized to come back to the relationship neurotransmitters have with sunlight and an over-production of melatonin.
For treatment, there’s strong evidence supporting the use of bright light therapy, cognitive behavioral therapy, and an FDA-approved antidepressant called Wellbutrin XL. But lately, there’s conversation around another potential preventative measure, something perhaps so obvious it’s been overlooked: food.
A casual internet search will bring up a motley crew of articles claiming specific foods ease “the winter blues.” Whether or not that is true is complicated. Research does indicate there is a robust link between nutrition and mental health. But there is no one food that is sure to fix the problem.
Michael Berk is a professor at Deakin University in Australia and a co-author of a now-influential study on the possible therapeutic impact of dietary changes on moderate to severe depression. The “SMILEs” trial did indicate diet is a useful strategy, and three studies have successfully replicated its results.
Regardless, Berk emphasizes “there is no superfood or super supplement.”
“The major misconception that people have is that there is a single superfood or supplement that is going to solve this problem,” Berk tells me. “The evidence does not support this. It really is about a healthy whole diet, and is as much about what you do not eat as what you do eat.”
Eating for mental health
The SMILEs trial leaned on a modified Mediterranean diet, which includes 12 key food groups. These include, but are not limited to, whole grains, vegetables, fish, and olive oil. “Extra” foods, like processed meats and sugar drinks, were limited to no more than three per week. All alcohol — apart from two standard drinks of wine per day — was placed in the “extra” group as well.
Choosing the Meditteranean diet wasn’t a random act. Previous studies suggest it can protect against the development of depressive symptoms in older people, and strict adherence is associated with a lower risk of being diagnosed with depression.
“The key is a healthy whole diet that is largely unprocessed, avoids industrial large processed foods, and is largely plant-based and fresh,” Berk says.
He notes that while his study examined the Meditteranean diet, a traditional Norwegian or Japanese diet “would be equally useful.” Both emphasize fresh food, very little sugar, and are heavy on the vegetables.
Why are vegetables so essential? Let’s zero in on leafy greens — think food like kale, collard greens, and spinach. Kathleen Holton is an associate professor at American University and a nutritional neuroscientist. She tells me that leafy greens are an excellent source of multiple micronutrients and are “very helpful in preventing depression due to the folate and vitamin C that they provide.”
She emphasizes that “micronutrient intake is essential for optimal mental health” because vitamins and minerals serve as important cofactors in the production of neurotransmitters. A deficiency in micronutrients, like vitamin D and magnesium, can cause abnormal neurotransmission with the potential to lead to mental illness, Holton says.
"Micronutrient intake is essential for optimal mental health."
Holton notes that magnesium-rich foods are “especially important for individuals suffering from anxiety disorders,” so “high magnesium foods are helpful in combating poor mental health.” These foods include seeds, nuts, salmon, and buckwheat. (Because fish is not commonly consumed in the US but is the best source of dietary vitamin D3, Holton recommends people use cod liver oil in the fall, winter, and spring seasons.)
Whiles studies that find a link between a healthy diet and positive mental health are increasing, there needs to be more research that examines nutrition and SAD specifically. A 2020 review published in the journal Frontiers in Psychology identified just 11 studies on the subject, none of which had impressive sample sizes or duration periods. Their conclusion was that there is insufficient evidence for using “nutrient supplementation” as a single intervention for SAD and hypothesize that a combined-approach — using nutrition and various forms of therapy — could be key.
Ultimately, this area of study is still in its infancy. Berk notes that, while one might expect there would be more information on the relationship between diet quality and mental health, the whole field of nutritional psychiatry is only a few years old. Still, he says, “it is rapidly gaining ground.”
A perhaps unexpected twist to consider: Holton says one of the biggest misconceptions she encounters is the idea that a vegan diet will help a mental health condition. However, multiple of the nutrients thought to contribute to optimal mental health, like vitamin D3 and B12, are only found in animal foods.
“Thus, a vegan diet might actually increase a person’s risk of mental illness due to the nutritional deficiencies it can cause.”