The microbiota-gut-brain axis: you are what you eat!
How many of us are maintaining a balanced diet during the quarantine of COVID-19 pandemic? Indeed, it is very challenging for everyone to keep a healthy diet while staying home. Limited groceries, reduced shopping times, and increased boredom (or anxiety) can motivate people to abandon their healthy eating intentions and consume whatever is around, including plenty of fast food and processed food. Also, people are facing more uncertainty in the midst of the pandemic, we don’t know what’s going happened next and how bad things might get. The growing anxiety threw our healthy eating plan to the wind, but you might have also noticed that the intake of an unbalanced diets can make a depressed mood worse. How does this happen? And what can we do about it?
The food we eat gives our bodies the nutrients they need to function properly. Those needs can differ among individuals with different family background, different dietary habits, and living in different countries. We need a variety of different foods, the ideal “balanced diet”, to provide enough nutrients for good health. Colorful fruits and vegetables, whole grains, beans, nuts, dairy products, seafood, lean meats and poultry are all suggested. However, the emergency of fast foods and processed foods are changing people’s eating habits to an unhealthy way. These foods are fancy, convenient but contain higher calories and low micronutrients. Their intake has been shown to strongly correlate with an increased risk of obesity, heart disease, type-2 diabetes and so on, which now put tens of millions of people at greater risk for COVID-19 complications. You might be also surprised to know that certain foods can impact our mood, in particular, anxiety levels.
A recent study carried out by scientists in Canada investigated the association between multiple factors and risk of developing anxiety [1]. They analysed approximately 26,991 participants who had been a part of the Canadian Longitudinal Study on Aging (CLSA) and found that people who have poor diet quality which are low in fruits and vegetables but high in fat and sugar are far more likely to be diagnosed with anxiety. Many earlier studies also supported that unhealthy diets like a high-fat diet can induce anxiety and depression. These observation studies made us aware of the undeniable link between diet and mental health. But how does this connection work?
Certain nutrients in foods increase the production of neurotransmitters such as serotonin (the “happy” hormone) and dopamine and make you “feel relaxed”. Evidence has shown foods enriched in zinc (e.g. oysters, liver and egg yolks), omega-3 fatty acids (e.g. fatty fish) and B vitamins (e.g. avocado and nuts) could reduce anxiety. Increasingly, more research has been conducted to understand how gut microbiota-the trillions of microorganisms in the gut that perform important functions in the metabolic and immune system-utilize and produce both macro and micronutrients to regulate the gut and brain health, which makes up the microbiota-gut-brain axis. It is found that anxiety can be alleviated by eating foods that promote healthy gut bacteria. There are several different routes of communication between diet, microbiota and brain, for example, when you eat nutrition-enriched food, the gut microbiota will produce neurotransmitters and short-chain fatty acids like butyrate. The butyrate has powerful anti-inflammatory effects and help reduce abnormal intestinal permeability (“leaky gut”). Low fiber, high-sugar and high-fat foods (collectively known as western diet) can perturb the normal gut microbiota, which causes less short-chain fatty acids to be produced. Ultimately, the gut barrier will become penetrable, and we can become more susceptible to infection and mental disorders.
The discovery of the microbiota-gut-brain axis has triggered intense interest in the application of microbial regulation on anxiety. Probiotics, offering specific healthy microbiota like Lactobacillus and Bifidobacterium, can be effective at reducing anxiety. Intriguingly, researchers at the Shanghai Medical Health Center reviewed 21 studies on the effect of food on anxiety [2]. They found that a prebiotic approach, consuming a diet with fiber enriched foods that selectively simulate certain bacterial populations in the gut, is more effective than taking probiotics with a poo diet. Important specific ingredients in prebiotics likely include culinary spices such as black pepper, cinnamon, ginger, rosemary and turmeric, and proanthocyanidins (PAs) enriched food like grapes, apples, blue berries, pecans and pistachio nuts.
In summary, promoting a diet diverse in fruits and vegetables as well as the use of pre- and probiotics can be effective to reduce anxiety and maintain a healthy mind. If I could offer one further piece of advice, drinking enough water to stay hydrated and regularly exercising will boost your immunity and may make you feel less anxious during this hard pandemic.
By Xiaoyuan Zhou
Sources:
The Gut-Brain Axis. You are what you eat! Source: BioRender (2020). Gut-Brain-Axis. Retrieved from https://app.biorender.com/biorender-templates/t-5ceff118a992a00035b823d7-gut-brain-axis