Why Food Affects Mood

Your brain gets a steady stream of information from your intestinal tract, where you digest food. What you eat can affect your mood. Learn more here.

The phrase “mind-body connection” betrays a long tradition of believing our minds exist outside our bodies. In fact, your mind is your experience of your brain, a part of your body. Your brain gets a steady stream of information from your intestinal tract, where you digest food.

Many foods, for example, are high in the amino acid tryptophan, including soy, cocoa powder, cashews, chicken breast, oats, and eggs. Evidence suggests that higher — but not the very highest — levels of tryptophan in your blood improve thinking and probably mood. One study even found that taking a tryptophan supplement might make some people more willing to give to charity.

Tryptophan competes with other amino acids to reach your brain, which limits how much you normally get from food. To see the full effects, in one double-blind study, researchers designed a drink formulated so tryptophan had unusually quick access to the brain. They then served it to a group of healthy young women who were hooked up to brain scans. With just one serving, the scans recorded desirable changes in their mental processing, including regulating activity in areas of the brain connected to mood.

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The reason might be that tryptophan converts in your body to serotonin — the brain chemical targeted in the most popular antidepressant drugs, selective serotonin reuptake inhibitors. You may be surprised to hear that 95 percent of the serotonin in your body is in your gastrointestinal tract, and that your gut contains more neurons than your spinal cord. Some people refer to those neurons as a “second brain.”

It’s more important than researchers previously thought. Scientists were surprised to learn that the vast majority of the fibers in the vagus nerve at the base of the skull — the entryway to your brain — carry information from your gut to your brain, rather than the other way around.

Your gut is home as well to tens of trillions of bacteria, which communicate with those neurons in still-mysterious ways. Your diet affects which bacteria flourish in your gut. In turn, evidence suggests the balance of gut bacteria affects mood and may play a role in mental and neurological healthy.

For example, an imbalance in gut bacteria can lead to chronic low-grade inflammation, an immune reaction, and slow the production of new brain cells — both tied to depression. You might say that the wrong diet makes your body behave almost as if it were fighting an infection, which drags down your mood.   

Researchers have found the connection between what happens in your digestive tract and your mood is more complicated than simply influencing inflammation levels. Mental disorders, including depression and anxeity, are often diagnosed along with gut problems. That suggests a two-way relationship between mental health and the microbiome in the digestive tract, according to a review of studies on the subject published in the journal Microorganisms.

In the not too distant future, as scientists continue to learn more how about how food impacts mood and mental health — including fermented foods that contain microorganisms that enhance beneficial bacteria in your gut —  specific foods may one day be part of a food “prescription” for better mental health.

Current favorite feel-good foods have emerged from centuries in which human beings tinkered with plants to enhance chemical properties people favor. Studies now back up what millions of people know: Dark chocolate and the caffeine in coffee and tea boost mood in many people. There’s also research indicating that fats in “comfort food” trigger signals from the gut to the brain that comfort us.

Other scientists are exploring the similarities between obesity and addiction, in which vulnerable people become increasingly attached to the emotional rewards triggered by a food or drug.

The best advice about which foods make you feel the best may be to pay attention to what you eat. Good health feels good, too.

Researchers who study the gut say it could be helpful to eat foods containing prebiotics and probiotics.

Prebiotics are typically high-fiber foods like whole grains, bananas, onions, and greens, which feed good bacteria in your gut. Probiotics are fermented foods, like sauerkraut and yogurt, which contain live microorganisms that help you maintain and improve the colony of good bacteria in your body.

Your best bet is to maintain your health and use food as a mood-booster sparingly. After a particularly tough day, a hot chocolate sundae could help temporarily, but over time cutting out sugar and eating more vegetables could make you feel far better. 

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