The next therapies for mental health may be found in your local supermarket.
Illustrations by Mark Marturello
IF YOU’VE EVER buried your sorrows in a bowl of fettuccine alfredo or indulged in chocolate for a dose of cheer, you’re living proof of the connection between food and mood. It seems second nature to turn to food to assuage mental distress, and science is now capitalizing on the ways food influences brain activity to create novel therapies for mental health. Clinicians and others who counsel patients on diet and nutrition can capitalize on this knowledge, too.
If it seems far-fetched to envision nutrition-based psychological interventions, think of the profound ways foods and beverages affect mood and behavior, even in the short term. Drink just enough coffee and you can count on a quick dose of energy and improved concentration. Drink one cup too many and you’re in for an hour of shakiness and heightened anxiety.
Or how about that comfort food? Maria Barnes, Ph.D., DMU assistant professor of biochemistry and nutrition, helps explain the neurological basis for why we eat carb-rich or sugary foods when we’re looking for a fast and easy mood-booster.
“Eating a high-fat meal — or even seeing a picture of a high-fat meal — stimulates the same reward centers of the brain that taking a drug does,” she says. “Signals from the gut that inform the brain of our nutritional status directly or indirectly impact dopaminergic neurons and their projections located in the reward center of the brain. Release of dopamine from its neuronal terminals is what makes us feel good after we eat comfort food, and the memory of how we felt when we ate it motivates us to eat more of it. This helps explain why the thought of certain foods or even the smell of food pushes us to eat…even when we’re not hungry.”
Barnes is quick to point out that this fast fix is just that — a temporary stress-buster — and that habitual consumption of high-fat foods can lead to negative physical outcomes such as cardiovascular disease and obesity, to name just a few.
On the other hand, accumulating evidence suggests that good nutrition is a basic requirement for good mental health, and that a number of neuropsychological conditions — chronic stress, anxiety disorders, major depressive disorders, autism spectrum disorders, bipolar disorder and even schizophrenia — are influenced by what we eat and drink. Let’s take a look at some of the most recent developments.
Good for the body, good for the mind
Research studies that investigate the best overall dietary patterns for good mental health invariably arrive at a not-so-surprising conclusion: the foods and beverages that support optimal physical health are the same ones that support optimal mental health.
Persuading patients to choose, say, fruits and vegetables over “comfort food” could enhance their state of mind.
A nine-year study of nearly 300 Canadians, using data from the Canadian Community Health Survey, found that a higher fruit and vegetable intake was associated with lower odds of both depression and anxiety – even after controlling for age, gender, income, education, physical activity, chronic illness and smoking.1
A 2013 study of 281 young adults found that their mood was better on days they ate more fruits and vegetables. Fruit and vegetable consumption predicted positive mood for the next day as well. Researchers suggest seven to eight daily servings of fruits and vegetables for positive mood.2
A study of more than 15,000 participants who were followed for an average of eight and a half years found that a higher adherence to the traditional Mediterranean diet, a mostly vegetarian diet, or the Alternative Healthy Eating Index-2010 diet was associated with a reduced risk of depression. What do all of these diets have in common? An emphasis on fruits and vegetables, nuts and legumes, monounsaturated fats such as extra virgin olive oil and polyunsaturated omega-3 fatty acids from fish, alcohol in moderation and little or no processed meats, refined carbohydrates and sweets.3
The Western diet, the norm for many Americans, may impair learning, memory and mood regulation.
Now, want a glimpse of the flip side? A fascinating study in Australia examined the impact of the Western diet — characterized by red meat, fried food and soft drinks — on the hippocampus, the area of the brain associated with learning, memory and mood regulation. Using MRI data, researchers measured volunteers’ hippocampal volumes at baseline and again four years later. They found that higher consumption of the Western diet was associated with a 52.6 millimeter³ smaller left hippocampal volume on average. These results were independent of age, gender, education, employment status, depressive symptoms and medication, physical activity, smoking, hypertension and diabetes.
The remedy? A healthy diet. Though some hippocampal volume naturally declines as we age, researchers found that every one standard deviation increase in a healthy dietary pattern — characterized by fresh fruits and vegetables, salad and grilled fish — was associated with a 45.7 millimeter³ larger left hippocampal volume.4
The old adage has proved true — we are what we eat. But we can also say that in a very real way, we think and feel what we eat.
From belly to brain: the gut-brain axis
There are roughly 100 billion neurons in the brain and about 100 trillion bacteria in the gut — and they all “talk” to each other. Research into the gut-brain axis — which refers to the biochemical signaling taking place between the gut microbiome and the central nervous system — is changing the way we approach mental health.
In a recent study based upon 710 young adults, researchers found that frequent consumption of fermented foods — yogurt, kimchi, tempeh, kefir, soymilk, sauerkraut, pickles, miso soup and even dark chocolate — significantly lowered symptoms of social anxiety, especially in those who were prone to neuroticism.5 Why? Fermented foods are chockfull of probiotics, the live bacteria that, according to numerous studies, act on the gut microbiome to confer antidepressant and anti-anxiety effects.6
Lead study author Matthew Hilimire, Ph.D., assistant professor of psychology at the College of William and Mary, helps explain how probiotics affect the gut-brain axis — and thus how they can play such an outsized role in mental health.
“The preclinical literature in animal models suggests various possibilities, most dependent on the vagus nerve,” he says. “For example, the gut becomes less leaky, inflammation is reduced, BDNF [brain-derived neurotrophic factor] levels are altered, GABA [gamma-aminobutyric acid] receptor expression is altered and response to stress is lowered. Anxiety has gastrointestinal symptoms, so reducing gut inflammation reduces that aspect of anxiety. GABA inhibits the nervous system, which alleviates anxiety.”
In a very real sense, then, calming the gut calms the mind.
Hilimire and his team speculate that fermented foods have an anti-anxiety effect above and beyond the probiotics found in supplements because of the presence of peptides and other chemicals that affect the brain. They also found that among the fermented foods they studied, yogurt emerged as the star of the show. “An unpublished secondary analysis of our data suggests that the [anti-anxiety] effect is mostly carried by more frequent consumption of yogurt,” he adds. “Note that not all yogurts contain live cultures, though, so if you’re interested in consuming probiotics through yogurt, look for a statement about containing active live cultures.”
Dietary fats and mental health: the good, the bad and the deadly
Learning which fats to embrace, which to indulge in just occasionally, and which to avoid like the plague will show patients how to have their cake and eat it too when it comes to mood and mental health.
We’ll start with the deadly: trans fats. There’s really no safe amount when it comes to these industrially produced substances meant to prolong the shelf life of commercially produced foods. Trans fats — which usually show up on food labels as partially hydrogenated oils — are highly inflammatory and have consistently been shown to contribute to cardiovascular disease, type 2 diabetes, high cholesterol, obesity and even Alzheimer’s disease. What’s more, trans fats have been specifically linked to depression, aggression and poorer cognitive function.
Saturated fats, while not quite as deleterious to health as trans fats, are still known to contribute to a litany of negative health outcomes, and diets high in saturated fat have been linked with an increased likelihood of depression, in part because they promote neuroinflammation and negatively alter the gut microbiome.7 Saturated fats come from sources such as butter, cheese and red meat. Those who do eat these foods should do so in moderation.
On the other hand, “good” fats — monounsaturated fats from sources like avocados and olive oil and especially the omega-3 polyunsaturated fatty acids (PUFAs) — have positive effects on brain health and mood regulation.
Epidemiological studies have shown that societies with a higher intake of seafood — which is rich in omega-3 PUFAs — have a lower prevalence of depression and mood disorders. Conversely, patients with major depressive disorder show lower levels of PUFAs. Depressed individuals also have higher levels of inflammatory biomarkers, and proinflammatory cytokines can actually lead to depression.8 Omega-3 PUFAs are found in abundance in fatty fish such as salmon, herring, mackerel, tuna and sardines.
For people who aren’t fans of fish, omega-3 supplements are readily available and have proven effective for good mental health. A meta-analysis of 19 randomized clinical trials found that omega-3 PUFA supplementation exerted significant clinical benefit for those with depressive symptoms, major depressive disorder and bipolar disorder.9 If you’re looking for vegetarian sources of omega-3 PUFAs to recommend to patients, walnuts, flaxseeds and their oils are all excellent options.
Getting thirsty yet?
When it’s time to wash down all those fermented foods and healthy fats, plenty of beverage options support mental health.
Wine enthusiasts will be pleased to learn that there is clinical evidence demonstrating wine’s positive effect on mood. A study of more than 5,500 adults in Spain found that drinking two to seven glasses of wine per week led to less depression. But moderation is key: the same study found that weekly alcohol consumption above this level actually contributed to depression.10
Drinking certain beverages in the right amounts can be a “toast” to one’s mental health.
Those who are teetotalers rather than tipplers have no need to worry: both coffee and tea boast an antidepressant effect. A 10-year study of 50,000 women found that those who drank two to three cups of caffeinated coffee a day were 15 percent less likely to experience depression than women who drank little or no coffee. The odds were even better for those who drank four or more cups a day. Overall, these Java Janes had a 20 percent lower risk of depression.11
Tea gets top marks for protecting against depression as well. A meta-analysis of 11 observational studies involving nearly 23,000 people found that for every three cups of tea (green or black) consumed per day, the risk of depression fell by 37 percent.12 A study on an elderly Japanese population — 1,058 individuals ages 70 and older — found that those who drank four or more cups of green tea a day experienced a 44 percent lower prevalence of depressive symptoms than those who drank one or fewer cups per day.13 This is good news for a demographic at higher risk for depressive disorders co-occurring with other serious illness.
The polyphenols in fruits and vegetables, which should make up half our plates, exert a positive effect on cognitive function.
How is it that wine, coffee and tea support mental health? Part of the credit goes to polyphenols, compounds from plant-based foods that exert a positive effect on cognitive function, synaptic plasticity, mood and neuronal function. There are hundreds of polyphenols in a wide array of foods, but they happen to be found in abundance in wine, coffee and tea, as well as in fruits, vegetables, cocoa and spices.14 Green tea is an excellent source of the class of polyphenols called catechins. Green tea catechins have been shown to decrease depressive symptoms, possibly through the inhibition of monoamine oxidase. The polyphenol resveratrol, present in red wine, red berries and grapes, exerts anti-depressive and anti-anxiety effects by inhibiting noradrenaline and serotonin reuptake while increasing hippocampal serotonin and noradrenaline levels.15 Plant polyphenols are also known to attenuate inflammation, and in animal models they’ve been shown to increase BDNF and promote neurogenesis.16 Lower levels of BDNF have been linked with depression as well as schizophrenia.
Finally, individuals who eschew both alcohol and caffeine won’t be left out in the cold: Even plain water can boost mood and ward off depression. A study of 120 healthy young women found that higher habitual water intake was associated with better moods. The women who drank the least water (about one and a half liters a day) had the highest scores on a test of mood disturbance, as well as a higher incidence of depression. On the other hand, the women who drank the most water (just over three liters a day) had the lowest mood disturbance scores, and also reported the least depression, tension and confusion.17
Other studies have found that even mild dehydration — a body water loss of 1 to 2 percent — causes poor concentration, short-term memory problems, moodiness and anxiety.18 Fortunately, these symptoms subside quickly after sufficient hydration. Advise patients to keep that water bottle handy, especially when they need to be on their A-game.
An apple a day
While we haven’t reached the point of prescribing probiotics over Prozac, research does demonstrate a clear link between what we eat and drink and how we think, feel and behave. And though more research is needed with human volunteers, there’s already a substantial body of evidence confirming that a healthy overall diet is as important to mental health as it is to physical health.
Guiding patients to make small but significant changes to their diet is also a low-cost, accessible way, for most people, to achieve positive outcomes. “Even satisfying your sweet tooth with a piece of fruit rather than ice cream is a great first step,” says Barnes. “Fruits like apples, strawberries and grapes can be very sweet, they are all natural, and you can receive the benefits of the polyphenolic compounds they contain.”
It turns out that supporting patients’ mental health really can be as easy — and as delicious — as their next trip to the supermarket.
Endnotes
1 McMartin, S.E., Jacka, F.N., Colman, I. (2013). The association between fruit and vegetable consumption and mental health disorders: Evidence from five waves of a national survey of Canadians. Preventive Medicine, 56(3): 225-230.
2 White, B.A., Horwath, C.C., Conner, T.S. (2013). Many apples a day keep the blues away – daily experiences of negative and positive affect in food consumption in young adults. British Journal of Health Psychology, 18(4): 782-798.
3 Sánchez-Villegas, A., Henríquez-Sánchez, P., Ruiz-Canela, M., Lahortiga, F., Molero, P., et al. (2015). A longitudinal analysis of diet quality scores and the risk of incident depression in the SUN Project. BMC Medicine, 13:197.
4 Jacka, F.N., Cherbuin, N., Anstey, K.J., Sachdev, P., Butterworth, P. (2015) Western diet is associated with a smaller hippocampus: a longitudinal investigation. BMC Medicine, 13:215.
5 Hilimire, M., DeVylder, J.E., Forestell, C. (2015). Fermented foods, neuroticism, and social anxiety: an interaction model. Psychiatry Research, 228(2): 203-208.
6 Evrensel, A., Ceylan, M.E. (2015). The gut-brain axis: the missing link in depression. Clinical Psychopharmacology and Neuroscience, 13(3): 239-244.
7 Bruce-Keller, A.J., Salbaum, J.M., Luo, M., Blachard IV, E., Taylor, C.M., et al. (2015). Obese-type gut microbiota induce neurobehavioral changes in the absence of obesity. Biological Psychiatry, 77(7): 607-615.
8 Su, K.P. (2012). Inflammation in psychopathology of depression: clinical, biological, and therapeutic implications. BioMedicine, 2(2): 68-74.
9 Grosso, G., Pajak, A., Marventano, S., Castellano, S., Galvano, F., et al. (2014). Role of omega-3 fatty acids in the treatment of depressive disorders: a comprehensive meta-analysis of randomized clinical trials. Malaga, G., ed. PLoS ONE, 9(5): e96905.
10 Gea, A., Beunza, J.J., Estruch, R., Sanchez-Villegas, A., Salas-Salvado, J., et al. (2013). Alcohol intake, wine consumption and the development of depression: the PREDIMED study. BMC Medicine, 11:192.
11 Seppa, N. (2015). The beneficial bean: coffee reveals itself as an unlikely health elixir. Science News, 188(7):16-19.
12 Dong, X., Yang, C., Cao, S., Gan, Y., Sun, H., et al. (2015). Tea consumption and the risk of depression: a meta-analysis of observational studies. Australian & New Zealand Journal of Psychiatry, 49(4): 334-345.
13 Niu, K., Hozawa, A., Kuriyama, S., Ebihara, S., Guo, H., et al. (2009). Green tea consumption is associated with depressive symptoms in the elderly. The American Journal of Clinical Nutrition, 90(6): 1615-1622.
14 Gomez-Pinilla, F., Nguyen, T.T.J. (2012). Natural mood foods: the actions of polyphenols against psychiatric and cognitive disorders. Nutritional Neuroscience, 15(3): 127-133.
15 Nabavi, S.M., Daglia, M., Braidy, N., Nabavi, S.F. (2015). Natural products, micronutrients, and nutraceuticals for the treatment of depression: a short review. Nutritional Neuroscience, epub ahead of print.
16 Jacka, F.N., Cherbuin, N., Anstey, K.J., Sachdev, P., Butterworth, P. (2015). Western diet is associated with a smaller hippocampus: a longitudinal investigation. BMC Medicine, 13:215.
17 Munoz, C.X., Johnson, E.C., McKenzie, A.L., Guelinckx, I., Graverholt, G., et al. (2015). Habitual total water intake and dimensions of mood in healthy young women. Appetite, 92:81-86.
18 Riebel, S.K., Davy, B.M. (2013). The hydration equation: update on water balance and cognitive performance. American College of Sports Medicine’s Health & Fitness Journal, 17(6): 21-28.
