For years, research on healthy eating has focused primarily on physical health and the relationship between diet, weight, and chronic disease. But the emerging field of nutritional psychiatry studies how food can make us feel.
"A lot of people think of food in terms of waistlines, but it also influences our mental health," says 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 begins in the womb. The gut and the brain originate from the same cells in the embryo, Naidoo said.
One of the main ways the brain and gut stay connected is through the vagus nerve, a two-way chemical messaging system that explains why stress can trigger anxious feelings in the mind and butterflies in the stomach.
Food can also influence the state of our microbiome, and some species of gut microbes have been linked to higher rates of depression.
Even serotonin, the brain chemical that regulates mood, has a strong connection to the gut. Only 5% of the body's serotonin is produced in the brain; the rest is made, stored and activated in the gut, said Naidoo, author of the new book What Food Does to Your Brain.
Nutritional psychiatrists say diet shouldn't replace other mental health treatments like therapy and prescription drugs, but it shouldn't be ignored either. Several studies indicate that dietary changes can lead to significant improvements in mood and mental well-being.
"We have to eat; it's a basic necessity," says Naidoo, who is also a professional chef and professor at the Cambridge School of Culinary Arts. "And food is also a very powerful tool when it comes to our mental health."
Dismantling a myth
People often try to influence their mood by eating so-called comfort food, such as ice cream, pizza or pasta. The problem, experts say, is that while these foods often offer a tempting combination of fats, sugars, salt, and carbohydrates that make them high-calorie, they can actually make us feel worse.
Traci Mann, who directs the Food and Health Laboratory at the University of Minnesota, conducted 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 answers were chocolate, ice cream and cookies. Respondents also rated foods they liked but wouldn't normally eat for comfort.
Before each trial, the participants watched movie clips that elicited anger, hostility, fear, anxiety, and sadness. After the movie, viewers filled out a "negative mood" questionnaire to indicate how they felt.
Next, they were given a hearty serving of their preferred comfort food; a food they liked but did not find comforting; a "neutral" food (a bar of oatmeal and honey); or no food. Everyone had three minutes alone to eat their food or sit quietly. After the break, they filled out the questionnaire about their mood again.
Whether a participant ate comfort food, any food, or no food made no difference to the person's mood. The factor that seemed to matter most was the passage of time.
"If you eat comfort food, he may feel better, but if he doesn't eat comfort food, he'll just feel better over time," Mann said. "People believe in comfort food and attribute to it an improvement in mood that would have happened anyway."
Using food to treat depression
Mann's research found that traditional comfort foods have no significant effect on mood. A growing body of research shows that improving the quality of a person's diet can have a significant effect on their mental health. An analysis of 16 studies revealed that nutritional interventions significantly reduce symptoms of depression.
The first intervention to test dietary changes as a treatment for depression included 67 patients, all of whom had poor diets consisting of many processed and sugary foods, with very little fruit, vegetables or fiber.
About half of the patients received nutritional counseling on a Mediterranean-style diet, as well as food baskets with food samples, recipes, and meal plans. The rest of the group met weekly for chat and peer support, but did not discuss the diet.
At the end of the three-month study, the diet group showed significantly greater improvement in depression symptoms, and a third of them had achieved complete remission, compared to just 8% in the social support group.
The effect has also been seen in larger studies. A four-year study of more than 10,000 university students in Spain showed that people who faithfully followed a Mediterranean diet had a lower risk of depression.
Australian researchers analyzed the food diaries of 12,385 adults who were part of a random sample from an ongoing government survey. They found that higher fruit and vegetable intake predicted greater happiness, life satisfaction, and well-being.
The psychological benefits were equivalent to going from being unemployed to being employed. And people who changed their diet to include more vegetables saw improvements in their mood within two years.
Much remains to be learned about which foods and how much of them can improve mental health. A year-long trial published in JAMA in 2019 concluded that a Mediterranean diet reduced anxiety but did not 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 clinical professor at Columbia University's Vagelos College of Physicians and Surgeons in New York.
Critical neurotransmitters and receptors are made when specific nutrients and amino acids are ingested, he said.
Glial cells, for example, which make up an important part of the brain, depend on omega-3 fats. Minerals, such as zinc, selenium, and magnesium, form the basis of brain tissue and cell activity, as well as the synthesis of neurotransmitters that directly affect mood. Iron, folate, and vitamin B12 help the body produce serotonin.
"Our brain evolved so that we would eat almost anything to survive, but we are seeing more and more clearly that there is a way to feed it to improve overall mental health," said Ramsey, author of the book Eating to Beat Depression and Anxiety.
"We know that if we eat a lot of junk, we feel really bad, but the idea that this extends to mental health risk is a relationship that we haven't made in psychiatry until recently."
Try some new "brain" foods
To help patients remember the best foods to support brain health, Ramsey has devised a simple mantra: "Seafood, vegetables, nuts and beans, and a little dark chocolate." He also teaches a free online cooking class (next one is February 7) called "Mental Fitness Kitchen."
For this week's Eating 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 regarding the possible brain benefits of various foods is still in its infancy, and eating these foods won't lead to mood swings overnight. But adding a number of these foods to your meals will improve the overall quality of your daily diet, and you may notice a difference in how you feel.
green leafy vegetables
Ramsey says that green leafy vegetables are the foundation of a brain health diet because they are cheap, versatile and have a high nutrient-to-calorie ratio. Kale is her favorite, but spinach, arugula, cabbage, beet greens, and Swiss chard are also great sources of fiber, folate, and vitamins C and A.
If you don't like salads, add vegetables to soups, stews, stir-fries, and smoothies, or turn them into a pesto. Ramsey also recommends adding a small serving of seaweed (the "sea greens") once a week as a source of additional iodine, fiber, zinc, and phytonutrients.
Colorful fruits and vegetables
The more colorful the plate, the better the brain food. Studies indicate that compounds in brightly colored fruits and vegetables, such as bell peppers, blueberries, broccoli, and eggplant, can affect inflammation, memory, sleep, and mood. Reddish-purple colored foods are very important in this category. And don't forget avocados, which are high in healthy fats that enhance the absorption of phytonutrients from other vegetables.
fish and shellfish
Sardines, oysters, mussels, wild salmon, and cod are sources of long-chain omega-3 fatty acids, essential for brain health. Fish and shellfish are also a good source of vitamin B12, selenium, iron, zinc, and protein. If you don't eat fish, chia seeds, flaxseeds, and sea vegetables are also good sources of omega-3s. For those on a budget, canned salmon is a more affordable option, says Naidoo.
Nuts, legumes and seeds
Try to eat between a half cup and a cup of legumes, nuts and seeds per day, says Ramsey. Nuts and seeds, such as cashews, almonds, walnuts, and pumpkin seeds, make a good snack, but can also be added to stir-fries and salads.
Black and red beans, lentils and legumes in general can also be added to soups, salads and stews or enjoyed as a meal or side dish. Nut butters also count.
spices and herbs
Cooking with spices doesn't just make food taste better. Studies also indicate that certain spices can 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 cognition in general. "Turmeric can be very powerful over time," she says.
"Try adding it to salad dressings or roasted vegetables," or including it in marinades, curries, sauces, stews, or smoothies. "Adding a pinch of black pepper makes curcumin 2,000% more bioavailable to the brain and body," she explained.
"It's an easy trick to do when cooking." Other spices that can support brain health include cinnamon, rosemary, sage, saffron, and ginger.
fermented foods
Fermented foods are made by combining raw milk, vegetables, or other ingredients with microorganisms such as yeasts and bacteria.
A recent study found that six daily servings of fermented foods can reduce inflammation and improve the diversity of the gut microbiome.
Fermented foods include yogurt; sauerkraut; kefir, a fermented milk drink; kombucha, a fermented beverage made from tea; and kimchi, a traditional Korean dish of fermented cabbage and radish. Coconut kefir is a non-dairy option.
Other fermented foods include miso, cottage cheese, Gouda cheese, and some types of apple cider vinegar. You can also take a small two-gram bottle of probiotics, which are sold in many health food stores.
Bitter chocolate
People who regularly eat dark chocolate have a 70% lower risk of symptoms of depression, 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 chocolate bars are so processed that they don't contain much epicatechin.
Tara Parker-Pope © New York Times
Translation: Elisa Carnelli
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