For years, research on healthy eating has focused primarily on physical health and the link between diet, weight and chronic disease. But the emerging field of nutritional psychiatry studies how foods can make us feel.
“Many people think about food in terms of their waistlines, but it also impacts our mental health,” said Uma Naidoo, a Harvard psychiatrist and director of nutritional and lifestyle psychiatry at Massachusetts General Hospital. “It’s a missing part of the conversation.”
The connection between the stomach and the brain is strong, and it starts in the womb. The gut and brain originate from the same cells in the embryo, Naidoo said. One of the main ways the brain and gut remain connected is through the vagus nerve, a two-way chemical messaging system that explains why stress can trigger feelings of anxiety in your mind and butterflies in your stomach.
Food can also influence the state of your microbiome, and some species of gut microbes have been linked to higher rates of depression. Even the brain chemical serotonin, which regulates mood, has a strong gut connection. Only 5% of your body’s serotonin is made in the brain; the rest is made, stored and active in the gut, said Naidoo, author of the new book “This Is Your Brain on Food.”
Nutritional psychiatrists say food shouldn’t replace other treatments for mental health, including therapy and prescription drugs, but it shouldn’t be ignored either. A number of studies have suggested that dietary changes can lead to meaningful improvements in mood and mental well-being.
“We have to eat; it’s a basic need,” said Naidoo, who is also a professional chef and instructor at the Cambridge School of Culinary Arts. “And food is also a very powerful lever in terms of our mental health.”
Debunking a Myth
Often people try to influence their mood by eating comfort foods such as ice cream, pizza or mac ’n’ cheese. The problem, experts say, is that while those foods typically offer a tantalising combination of fat, sugar, salt and carbs that make them hyperpalatable, they can actually make us feel worse.
Traci Mann, who heads the health and eating laboratory at the University of Minnesota, ran a series of studies to determine whether a person's preferred comfort food improves their mood. Participants were asked the following question: “What foods would make you feel better if you were in a bad mood?”
The most-common responses were chocolate, ice cream and cookies. The respondents also rated foods they enjoyed but would not normally eat to seek comfort.
Before each test, the participants watched film clips that were known to elicit anger, hostility, fear, anxiety and sadness. After the film, the viewers filled out a “negative mood” questionnaire to indicate how they were feeling. Then they were given a heaping portion of their favourite comfort food; a food they liked but didn’t view as a comfort food; a “neutral” food (an oat and honey granola bar); or no food at all. Everyone had three minutes alone to eat their food, or sit quietly. After the break, they filled out the mood questionnaire again.
Whether a participant ate comfort food, any food or no food didn’t make a difference in the person's mood. The factor that seemed to matter most was the passage of time.
“If you eat comfort food, you might feel better, but if you didn’t eat it, you would also feel better just with time going by,” Mann said. “People believe in comfort food, and they are giving it credit for mood improvements that would have happened anyway.”
Using Food to Treat Depression
Mann’s research found that traditional comfort foods don’t have a meaningful effect on mood, a growing body of research shows that improving the quality of a person’s diet can have a significant effect on mental health. An analysis of 16 studies found that dietary interventions significantly reduced depression symptoms.
The first intervention to test dietary changes as a treatment for depression included 67 patients, all of whom had poor diets consisting of a lot of processed and sugary foods, with very little fruits, vegetables or fibre. About half the patients were given nutrition counselling for a Mediterranean-style diet, as well as food baskets containing sample foods, recipes and meal plans. The rest of the group met weekly to chat and receive friendly support, but diet wasn’t discussed. At the end of the three-month study, the food group showed significantly greater improvement in depression symptoms, and a third of them had achieved full remission, compared to just 8% of the social support group.
The effect has been seen in larger studies, too. A four-year study of more than 10,000 university students in Spain found that people who closely followed a Mediterranean diet were at lower risk for depression. Australian researchers examined food diaries of 12,385 randomly sampled adults from an ongoing government survey. They found that higher fruit and vegetable intake predicted increased happiness, life satisfaction and well-being. The psychological gains were equivalent to moving from unemployment to employment. And people who changed their diet to include more vegetables saw mood improvements within two years.
There’s still much to learn about which foods and how much of them can improve mental health. One yearlong trial published in JAMA in 2019 found that a Mediterranean diet reduced anxiety but didn’t prevent depression in those at high risk.
Scientists know that about 20% of everything we eat goes to the brain, said Drew Ramsey, a psychiatrist and assistant clinical professor at the Columbia University Vagelos College of Physicians and Surgeons in New York. Critical neurotransmitters and receptors are made when you eat specific nutrients and amino acids, he said. Your glial cells, for example, which make up a substantial portion of the brain, are dependent on omega-3 fats. Minerals including zinc, selenium and magnesium provide the foundation for cell activity and brain tissue and the synthesis of neurotransmitters that directly affect mood. Iron, folate and vitamin B12 help your body produce serotonin.
“Our brains evolved to eat almost anything to survive, but increasingly we know there’s a way to fuel it to improve overall mental health,” said Ramsey, author of the book “Eat to Beat Depression and Anxiety.” “We know if you eat a bunch of garbage, you feel like garbage, but the idea that it extends into our mental health risk is a connection we haven’t made in psychiatry until recently.”
Try some new ‘brain’ foods
To help patients remember the best foods to eat to support brain health, Ramsey has devised a simple mantra: “Seafood, greens, nuts and beans — and a little dark chocolate.” He also hosts a free online cooking class (the next one is Feb 7) called “Mental Fitness Kitchen.”
For this week’s Eat Well Challenge, try adding some new foods to your plate that have been linked to better brain health. This list is based on suggestions from Naidoo and Ramsey. Much of the science on the possible brain benefits of various foods is still in its early stages, and eating these foods won’t result in mood changes overnight. But incorporating several of these foods into your meals will improve the overall quality of your daily diet — and you might notice a difference in how you feel.
Leafy greens: Ramsey calls leafy greens the foundation of a brain health diet because they’re cheap, versatile and have a high ratio of nutrients to calories. Kale is his personal favourite, but spinach, arugula, collards, beet greens and chard are also great sources of fibre, folate and vitamins C and A. If you’re not a fan of salads, add greens to soups, stews, stir fries and smoothies, or turn them into a pesto. He also recommends adding a small serving of seaweed (the “leafy green of the sea”) to your plate once a week as a source of iodine, fibre, zinc and additional phytonutrients.
Colourful fruits and vegetables: The more colourful your plate, the better the food is for your brain. Studies suggest that the compounds in brightly coloured fruits and vegetables like red peppers, blueberries, broccoli and eggplant can affect inflammation, memory, sleep and mood. Reddish-purplish foods are “power players” in this category. And don’t forget avocados, which are high in healthy fats that enhance the absorption of phytonutrients from other vegetables.
Seafood: Sardines, oysters, mussels, wild salmon and cod are sources of long-chain omega-3 fatty acids that are essential for brain health. Seafood is also a good source of vitamin B12, selenium, iron, zinc and protein. If you don’t eat fish, chia seeds, flax seeds and sea vegetables are also good sources of omega-3s. For those on a budget, canned salmon is a more affordable option, said Naidoo.
Nuts, beans and seeds: Try to eat between a half cup and a full cup of beans, nuts and seeds a day, says Ramsey. Nuts and seeds, including cashews, almonds, walnuts and pumpkin seeds, are a great snack, but they can also be added to stir fry dishes and salads. Black and red beans, lentils and legumes can also be added to soups, salads and stews or enjoyed as a meal or a side dish. Nut butters count too.
Spices and herbs: Cooking with spices not only makes your food taste better, but studies suggest certain spices may lead to a better balance of gut microbes, reduce inflammation and even improve memory. Naidoo especially likes turmeric; studies suggest that its active ingredient, curcumin, may have benefits for attention and overall cognition. “Turmeric can be very powerful over time,” she said. “Try incorporating it into your salad dressing or roasted vegetables,” or adding it to marinades, curries, sauces, stews or smoothies. “Adding a pinch of black pepper makes curcumin 2,000% more bio-available to our brain and body,” she said. “It’s an easy hack to do when you’re cooking.” Other spices that may support brain health include cinnamon, rosemary, sage, saffron and ginger.
Fermented foods: Fermented foods are made by combining milk, vegetables or other raw ingredients with microorganisms such as yeast and bacteria. A recent study found that six servings a day of fermented foods can lower inflammation and improve the diversity of your gut microbiome. Fermented foods include yogurt; sauerkraut; kefir, a fermented milk beverage; kombucha, a fermented drink made with tea; and kimchi, a traditional Korean side dish of fermented cabbage and radish. Coconut kefir is a nondairy option. Other fermented foods include miso, cottage cheese, Gouda cheese and some types of apple cider vinegar. You can also drink probiotic-containing “gut shots,” which are small bottles of fermented beverages, usually about two ounces in size, sold in many grocery stores.
Dark chocolate: People who regularly eat dark chocolate have a 70% reduced risk of depression symptoms, according to a large government survey of nearly 14,000 adults. The same effect was not seen in those who ate a lot of milk chocolate. Dark chocolate is packed with flavonols, including epicatechin, but milk chocolate and popular candy bars are so processed that they don’t have much epicatechin left in them.
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