Food for Thought: Can What We Eat Influence Our Mental Health?

We dug into the latest research in nutritional psychiatry to find out.

When the pandemic hit, Jenny Lee headed to the grocery store like everybody else, stocking up on dry pasta, canned sauces and frozen food—mostly processed foods with a long shelf life. “Not only were we in a really bad situation, we were eating like shit,” says the 36-year-old from Stoney Creek, Ont. It’s not like Lee had never used a canned pasta sauce to pull together dinner before, but the frequency with which she was cooking with processed foods increased as she worked her way through the stockpile.

Her diet was also less diverse than when she’d been able to go out and grab a salad at lunch. And she just felt bad—her anxiety spiked, she wasn’t sleeping, she felt constantly sluggish as a result, and then felt guilty for not being able to care for her toddler, Miles. “They tell you that, at two, [kids] should only have an hour of screen time—I was like, yeah, not during COVID,” says Lee. “We were just surviving.”

It made sense she was tired and anxious. Miles was home from daycare and both Lee and her husband were working from home, juggling video-call schedules so someone was always able to watch Miles. What didn’t make sense was how bloated she was. By the fall, she felt like she was five months pregnant—Lee could barely bend over because her stomach was so distended. She also had other symptoms she recognized as anxiety, like tightness in her jaw, numbness in her limbs and heart palpitations. Lee was used to dealing with anxiety, but the pandemic kicked it into high gear and the physical symptoms she was experiencing concerned her.

She saw her family doctor and went down several investigative rabbit holes—blood tests, an ECG, tests examining her organ functionality. There didn’t seem to be an underlying problem. Then she went on a high-gluten diet for three months to test for celiac disease, and that’s when she noticed the impact of upping her intake of bread, pizza and pasta was having on her. “My anxiety just skyrocketed,” Lee says. “It felt like suffocation—like I couldn’t even get a full breath in.”

(Related: 8 Women Share the Impact the Pandemic Has Had on Their Mental Health

She started working with a naturopath last fall, who encouraged her to eat more anti-inflammatory foods and cut out refined sugar to heal her gut. But it wasn’t until she started seeing a therapist a few months later that she really started to understand the connection between what she ate and how she felt. During the first two sessions, Lee’s therapist asked about her diet, and worked with her on how she could add healthy foods like fresh vegetables, and crowd out others, like processed foods.

Lee and her therapist are not alone in using food as one tool to combat mental health concerns like depression and anxiety. There is increasing evidence of a relationship between what you eat and your mental health. As we learn more about the gut-brain connection, some researchers say the makeup of your gut microbiome—the unique mix of bacteria, fungi and other micro-organisms—can impact mental health, and that diet might play a considerable preventative role when it comes to conditions like depression, anxiety and ADHD. The way you eat can also impact brain plasticity—the ability your brain has to make new connections, adapt and grow. This is all informing the approach of nutritional psychiatry, a burgeoning field in mental health research—one that might radically change how we think about the connection between food and mood.

Nutritional psychiatrists, like Dr. Uma Naidoo, director of nutritional psychiatry at Massachusetts General Hospital, use reorienting a patient’s relationship to food as an additional tool to help manage their patients’ mental health concerns. “It’s not an overnight fix or a cure-all,” says Naidoo, who is on the faculty at Harvard Medical School and the author of This is Your Brain on Food. “It’s a slow and steady lifestyle change.”

Guidance is lagging behind evidence

Lee’s family doctor told her to “eat better” but didn’t really break down what that means or why. And that’s a common experience—people aren’t generally given dietary tips as part of their mental health treatment plan. While a psychiatrist or therapist might ask if you have an appetite, it’s much less common that they ask what you’re eating. Which is funny, considering that for physical ailments like heart disease, doctors usually advise patients to cut simple carbs and sugar and eat more fresh produce.

Dr. Drew Ramsey, a nutritional psychiatrist and assistant professor of psychiatry at Columbia University, says one reason food isn’t talked about at the doctor’s office in relation to mental health is that the evidence illuminating the importance of the gut-brain connection and its implications for mental health is relatively new.

While there have been some exciting studies over the last decade showing a correlation between diet and mental health, they were often small, and not randomized control studies—the gold standard in scientific inquiry. But a 2017 study changed that. The SMILES study out of Australia was a significant one, as it was the first randomized control trial seeking to answer the question, “If I improve my diet, will my mental health improve?”

Led by Felice Jacka, director of the Food and Mood Centre at Australia’s Deakin University, the 12-week study followed 67 participants—33 in the intervention group, and 34 in the control group. Those who participated were all over 18, all were experiencing a major depressive episode and scored low on a scale measuring diet quality—meaning they weren’t eating much fibre, lean protein, or fruit and veggies, and their diet was high in sweets, processed meat and salty snacks.

One group received dietary counselling from a clinical dietician over seven sessions—weekly during the first four weeks, then every other week. Those who were part of the dietary support group were given serving suggestions for 12 specific food groups, including whole grains, fruits and vegetables, nuts, fish and eggs, and were asked to give up refined sugar, fried food and processed meats. The control group was also provided with a session of the same length and frequency, but the goal was stated to be social support, i.e., creating the feeling someone was “befriending” them.

Both groups filled out a depression rating scale before and after the intervention, and participants’ scores after 12 weeks were compared to their baseline score. Almost a third, 32 percent, of those in the dietary group were in remission from their depression, compared to 8 percent in the social support, a difference the researchers found to be statistically significant. It’s also a meaningful result because some participants were already being treated for their depression, says Ramsey.

The mind-gut connection

When Lee first spoke to her family doctor about how she was feeling, she was given prescriptions for an anti-depressant and three other medications to deal with the physical symptoms she was experiencing. She wanted to get her anxiety under control, and while Lee isn’t anti-medication, she wanted to try something she felt was more natural first.
Nutritional psychiatrists like Ramsey and Naidoo see diet as one more tool that can be used to manage mental health issues—they each also provide psychotherapy and prescribe medication, which, in addition to dietary guidance, can be part of a treatment plan.

Researchers are now exploring the implications of the gut-brain connection on our ability to treat disorders like depression. The vagus nerve connects the gut and the brain, delivering messages both ways, and is the main part of the parasympathetic nervous system, which helps regulate your immune system, mood, digestion and more.

Your gut microbiome—the trillions of bacteria, viruses and fungi hanging out inside you—is unique to you, which helps explain why people react differently to certain foods, and why something like a low-carb diet doesn’t have the same effect on everyone. It turns out that the makeup of your microbiome may also have an impact on your mental health.

An illustration of a figure inside a gut with microbes floating around, meant to illustrate the mind-gut connectionImage: Gracia Lam

And that might start before you’re born. “Our results suggest that, during pregnancy, maternal adherence to the Mediterranean diet—rich in legumes, vegetables, fish, and healthy fatty acids, and lower in red meat—may promote behavioural and emotional well-being in children,” reads a 2018 study of 325 mother-child pairs in the United States. And the inverse has also been found. A 2013 study by Jacka and others of over 23,000 mothers and children in Norway found that unhealthy diets during pregnancy were correlated with behavioural and emotional problems in their children.

But evidence also suggests that your microbiome isn’t static; you can influence the makeup of your microbiome with what you eat.

While Naidoo is excited about further research on the gut-brain connection and the implications it may have for diet, she notes that “nutritional science is very uniquely underfunded compared to pharmaceutical drug trials.” She adds that collecting data on diet is difficult for a number of reasons, including that it’s hard to get people to accurately recall what they ate and compare it to a modified diet. And although the SMILES trial was encouraging, Naidoo notes it was still a pretty small number of subjects.

While many of these findings still need more research to support them unequivocally, we have amassed enough evidence to encourage a move away from the typical North American diet, which is high in salt, sugar and saturated and trans fat.

The problem with the Western diet

“People are eating things in packages instead of eating real food,” says Bonnie Kaplan, a professor emerita at the University of Calgary’s Cumming School of Medicine. By real food, Kaplan means the kind of food her parents and grandparents ate: fresh fruits, vegetables, legumes, nuts and fish.

There is evidence that a Western diet isn’t just contributing to obesity and heart disease, but that it’s associated with increased likelihood of experiencing anxiety, depression and cognitive issues.

“A lot of folks are living in a brain-food desert,” says Ramsey. “There’s a lot of food and a lot of calories, but there aren’t the foods that are best for our health and our mental health.”

(Related: Canada’s Dietitians Are Lacking in Diversity–But Things Are Changing

A 2020 review of the evidence in the journal Frontiers of Psychology in relation to the Western diet and brain function is clear: “A [Western diet] rich in fats, sugar, and salt alters gut microbiota composition and is associated with obesity, chronic inflammation, allergies, diabetes, autoimmune disorders, depression, metabolic syndrome, and neuropsychiatric disorders.”

There is also evidence that a diet high in sugar and saturated fat contributes to inflammation, which may in turn contribute to both depression and anxiety. Inflammation is one way the body heals itself, like the swelling that occurs around a wound when you cut yourself. But sometimes the body can create chronic inflammation, which can lead to many different illnesses, including mood disorders. “Inflammatory factors cause more depression, but as you get depressed your inflammatory factors go up,” says Ramsey. But certain foods, such as leafy greens rich in folate, can reduce or regulate inflammation.

A diet high in processed food is simply not giving the brain what it needs to perform optimally, write Kaplan and psychologist Julia Rucklidge in their book The Better Brain. They make the argument that the lack of nutrition in the Western diet has led to a lack of resilience. We aren’t more stressed or depressed than previous generations, but because of our lack of micronutrients, we aren’t able to withstand the impact of stressors as well as previous generations.

There’s no magic bullet

Research often focuses on one vitamin or mineral’s effect on one condition or disease, but Kaplan says that’s where science has us tripped up—it’s about a whole range of nutrients we need.

When we talk about nutrition, we’re almost exclusively taking about macronutrients: carbs, proteins, fats—the stuff you see on nutrition labels at the grocery store. Kaplan and Rucklidge argue we don’t talk about micronutrients enough, which are another set of vitamins and minerals, like omega-3 fatty acids, zinc and folate. Evidence shows broad-spectrum multinutrients have more benefits for mental health conditions compared to multinutrients with limited vitamins and minerals. Kaplan and Rucklidge encourage broad-spectrum supplements in addition to dietary changes to stock up on these micronutrients we may not be getting in our diet.

Ramsey takes a different approach, preferring that patients get their nutrients from food—which has elements to offer that a pill doesn’t, like fibre, bacteria and phytonutrients.

What foods feed the brain 

Along with Dr. Laura LaChance, a psychiatrist and lecturer at McGill University, Ramsey undertook a systematic review of research on nutrients that help prevent and treat depression by analyzing 213 studies to find which nutrients out of a list of 34 had clinical evidence that could support prevention of and recovery from depression. From this, they created the Antidepression Food Score. They found 12 nutrients were particularly important to brain health: folate, iron, long-chain omega-3 fatty acids (EPA and DHA), magnesium, potassium, selenium, thiamine, vitamin A, vitamin B6, vitamin B12, vitamin C and zinc. And they also identified the top foods that contained these nutrients, including oysters, leafy greens and peppers.

Researchers—including Kaplan, and Naidoo and Ramsey—broadly agree that the Mediterranean diet is not only great for your physical health, but also for brain health. This includes fish, nuts, seeds, fresh fruits and vegetables, legumes and olive oil, among other food. These foods are rich in a number of the nutrients identified by Ramsey and LaChance, ranging from oysters high in iron, which helps produce serotonin and dopamine, to chickpeas high in vitamin B6, which can help prevent inflammation.

In his book Eat to Beat Depression and Anxiety, Ramsey offers a six-week plan for those who want to incorporate more of these nutrients into their diet. He suggests introducing one new category a week—the first week is leafy greens, with suggestions for how to get things like kale, spinach and watercress into more meals, along with recipes like a green shakshuka. The second week moves to add more “rainbows” to meals—a variety of fruits and veggies like broccoli, bell peppers and eggplant. Week three is seafood, the following week tackles nuts, beans and seeds, and finishing with fermented food on week five. (Week six encourages readers to examine their “food roots”—where does your food come from and what is your connection to it?)

Kaplan and Rucklidge advise using the 80-20 rule: eat nourishing foods 80 percent of the time, and enjoy other foods—without worrying about nutrients—for the remainder.

One concern that often comes up with moving towards fresh foods and away from processed food is that they cost more. But eating well doesn’t have to be expensive—Ramsey shopped at Walmart while writing his book to ensure the tips and recipes he included were accessible. He created a guide, on his website, on how to eat healthy on a budget, encouraging people to buy in bulk where it makes sense, and not to shy away from frozen items like fish, fruit and veggies. He also notes that one of the unexpected outcomes of the SMILES trial was that participants saved over $100 a month on food when they switched to a healthier diet.

What we don’t know yet

A 2019 review of the existing literature on nutritional psychiatry found much of what has been observed is correlation, not causation—nor do we have a deep understanding the underlying factors. Additionally, many of the studies have been too small or not randomized, so generalization isn’t always appropriate until we have more randomized control trials.

Further, personalized medicine, whereby a treatment plan is tailored to a patient based on unique factors like their genome sequence, is an exciting field of research and commercial possibility, but researchers say there isn’t enough evidence for its application yet in this sphere. There also isn’t enough evidence to know whether the companies offering to sequence your microbiome to provide an optimal custom diet might actually be effective, or even how to personalize diets or supplements yet (although studies have shown certain bacterial strains are present in those with ADHD or schizophrenia, and that certain microbes are missing in people who are depressed). “Even if you got your own gut microbiome analyzed, it’s too soon to know which [bacterial] strains could correct any specific mental health problem,” write Kaplan and Rucklidge in The Better Brain.

(Related: How to Build a Strong Microbiome to Improve Your Gut Health

Kaplan points out that what she might need for optimal serotonin conversion might be different from anyone else. “There’s no test in the world for that yet,” says Kaplan, adding that’s why she advocates the broad-spectrum approach to taking multinutrients as a second step to a whole-food-first approach. “It’s a shotgun approach, but it’s a safe shotgun approach.”

While personalized medicine isn’t an option, food plans are slowly becoming part of mental health plans—the Food as Medicine program run by the Mood Disorders Association of B.C. is one example. Since 2016, psychiatrist Dr. Leslie Wicholas has used dietary interventions with her patients, working with about 450 people. She recently presented findings from 157 patients who participated in an eight-week program, 80 percent of whom had moderate to severe symptoms of depression. There were two groups, one with a primary diagnosis of depression, the other with fibromyalgia. After weekly two-hour sessions led by Wicholas and a naturopath, both groups had statistically significant improvement in their depressive symptoms.

“Positive treatment outcomes in depression were correlated to how closely people followed the dietary recommendations—those who followed the directions completely tended to respond better,” writes Wicholas in an email.

For Ramsey, there’s additional appeal in encouraging a patient who is feeling really low, if they can afford it, to just go ahead buy that $9 salad they love rather than trying to put a meal together themselves when they don’t have the energy. “Maybe the medication is going to take a month to work, maybe my interpretation about you and your family and relationship problems is going to take years,” he says. But having a healthy meal is going to be immediately satisfying. “At the end of that meal, you’re like, ‘I really like that and I know that these foods are good for my mental health.”

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Originally Published in Best Health Canada