Do the mixed messages about whether coffee is healthy leave you dithering about your morning cup of joe? If, like me, you need a good cup of coffee to start your day with gusto, it may be helpful to know that your response to coffee hinges on your genes. Some people have genetic variants that set them up to process caffeine quickly while others are “slow metabolizers,” meaning that coffee can make them jittery and anxious.
Coffee connects with your brain, potentially cranking it up and helping you to think more clearly. It can also lift your mood by, for instance, boosting levels of certain feel-good neurotransmitters. Accordingly, some studies show that drinking more coffee (and green tea) lowers the risk of depression.
- Coffee Supports Gut Health
Now we’re learning some of these benefits may spring from coffee’s impact on your gut bacteria. The gut is your “second brain:” The two are connected by a biological superhighway known as the gut-brain axis. Gut bacteria manage the flow of chemical messengers on this two-way route. They also produce some mood-enhancing substances themselves — for instance, about 90 percent of your body’s supply of serotonin (known as the happy hormone).
Coffee plays on this team because it’s high in phytonutrients, including polyphenols. Polyphenols are establishing a reputation as “superfoods” for your friendly gut bacteria. Research shows that drinking coffee diversifies these bacterial settlers, which supports emotional equilibrium.
Coffee is also high in antioxidants, which support the growth of bacteria that fight inflammation. Not only are people suffering from depression likely to show markers of inflammation, but their gut microbes also differ from those residing in healthier individuals.
- Microbes Shape Your Mood
Research shows that supplementing with specific strains of bacteria diminishes depression in certain individuals. Moreover, numerous studies indicate that fecal transplants of “healthy” or “depression-related” bacteria can alter behavior accordingly. Some researchers believe that unhealthy guts spark depression, in part by disrupting how the body processes certain nutrients.
Consider tryptophan. This essential amino acid that stimulates activity on the gut-brain axis, sparking serotonin production. Tryptophan helps to control inflammation and low blood levels of tryptophan are associated with anxiety and depression.
Basically, your gut bacteria mediate how your body processes tryptophan. A healthy microbiome makes efficient use of the tryptophan you provide but bacterial imbalance compromises your body’s ability to process the nutrient. Unsurprisingly, one study showed that supplementing with a specific probiotic fuelled the production of tryptophan.
- A Healthy Gut Keeps You Grounded
When your microbial ecosystem is humming along (with friendly bacteria in control), it’s producing neurotransmitters that help to keep you grounded. On the other hand, when “bad guys” dominate you are more vulnerable to losing a battle with the blues.
And here’s an ironic twist: Stress makes you vulnerable to craving foods that upset your microbial applecart. Studies show that distressed people prefer sweet or high-fat foods because they stimulate pleasure centers in the brain. Unfortunately, they can also reshape the bacterial composition of your gut, eroding your ability to handle stress.
Scientists have been surprised by how quickly a fast-food diet triggers an inflammatory response and sends your microbes heading south. After 10 days of eating only processed foods, one subject lost nearly half of the bacterial species residing in his gut. Predictably, research has linked fast food intake with the probability of feeling depressed.
- A Mood Boosting Diet
We’ve long understood the connections between mood and food — for instance that consuming complex carbohydrates like whole grains and legumes helps to keep you on an even keel. But now branches of science like nutrigenomics are identifying how these biological pathways work. The possibility of using “psychobiotic diets” to treat mood disorders is looming on the horizon and a new specialty, “nutritional psychiatry,” is springing up at medical institutions around the world.
While beneficial bacteria can support the brain, the body is an extremely complex system. Scientists acknowledge it’s doubtful we’ll find a magic microbial bullet that works for everyone. Similarly, if you’re keen to keep the blues at bay, focusing on specific mood-enhancing foods like coffee, green tea and dark chocolate is too limited. For many reasons the best strategy for buttressing emotional health is simple and two-pronged: avoid ultra-processed foods and eat a balanced diet featuring plenty of plant foods.
Research shows that eating a plant-focused diet for as little as one day boosts the ratio of “good guy” bacteria in your gut. The Mediterranean diet (focused on plant-based foods like whole grains, fruits, vegetables, legumes and nuts, plus healthy fats obtained mainly from fish and olive oil) is one of the most studied dietary approaches. It’s been shown to raise the ratio of beneficial gut bacteria and build resilience to stress.
Moreover, the Mediterranean Diet has been specifically linked with relief from depression. Nutritional psychiatry is rapidly developing but the preliminary findings are compelling. You can eat to beat the blues, in part because the friendly critters residing in your gut will help you to achieve that goal.
Judith Finlayson is the author of You Are What Your Grandparents Ate: What You Need to Know About Nutrition, Experience, Epigenetics, and the Origins of Chronic Disease. Visit her at www.judithfinlayson.com.