The French lawyer Jean Anthelme Brillat-Savarin made a famous quote back in the late 18^th century: “Tell me what you eat, and I will tell you what you are.” In many ways, this statement reigns true when it comes to brain health. There are many foods that you can eat to improve brain function or drinks that can help you endure a long day at work. Diving deeper, science has begun to identify links between what you eat and the chances of you developing a cognitive or mental disorder. In this article, we will explore the research that examines these connections, endeavoring to answer: What's the link between your diet and mental health? How does what you eat affect cognitive functions, such as memory? How are the gut and central nervous system (CNS) linked, and why is this important? Are there specific foods or medical products that can keep your gut healthy and put you in a better mental space?

Diet and mental health

What you eat affects how you feel. Medical practitioners have long suspected a range of foods likely to cause headaches when eaten in excess, including sugar. High blood sugar levels have also been connected with anxiety, possibly linked to increased sugar cravings and blood sugar imbalances. In the spirit of these findings, multiple studies have also connected the overall composition of one’s diet to mental health outcomes: 

• The research linking diet to mental health issues has been growing for decades. A 2002 study determined that at the country scale, higher sugar consumption was associated with an increased rate of clinically diagnosed depression.
  
• A 2006 study determined that drinking copious amounts of sugar-containing soft drinks was positively correlated with mental health problems among adolescents. This included an increased prevalence of mental distress, problems with conduct, and hyperactivity.
  
• Diets distinguished by excessive sugar consumption drive inflammation, which has been  correlated with worse mental health, as determined in a 2014 systematic review of 12 epidemiological studies. Diets characterized by an excess intake of fats and sugars may actually result in malnutrition from an insufficient intake of essential nutrients (e.g., zinc, magnesium, vitamins) that are vital for cognitive functioning as well as overall physical health.
  
• Increased sugar consumption has also been linked with the occurrence of other mental health disorders. A 2018 study determined that increased dietary intake of refined sugar worsened the severity of schizophrenia and two-year outcomes of the disease. 

Diet and cognitive health

With diet having such strong effects on mental health, it stands to reason that the what you eat can also impact your cognitive functions: 

• A 2016 systematic review of five randomized control trials (RCTs) and 27 observational studies determined that adopting the Mediterranean diet reduced the risk of dementia and Alzheimer’s. In contrast, eating too much sugar or artificial sweeteners was associated with an increased risk of ischemic stroke and dementia.
  
• A 2020 mini-review that examined nine RCTs between 2017 and 2020 determined that people who adopted a healthy diet demonstrated enhanced cognitive functions, including memory functions and processing speed. These foods included omega-3 supplementation and foods typical of a plant-based diet.
  
• A 2017 mouse model study demonstrated that the mice that consumed a high-fat diet and sugary drinks had impaired brain insulin signaling, which led to inflammation of the nerves mediating brain activity and increased risk of Alzheimer’s disease pathology. Multiple studies have demonstrated similar findings among mice fed with a high-fat diet.
  

The gut-brain axis: Linking what you eat and brain function

The human body is an interconnected system that features interactions between all of its organs. Many of these interactions are bidirectional, meaning that the organs interact with each other in a two-way system. The gut-brain axis is one of these bidirectional systems, mediated by a subset of nerves called enteric nerves. Multiple mechanisms contribute to the everyday operations of the gut-brain axis. Each of these mechanisms involves the trillions of living microorganisms that reside in your gut. 

• Satiety control: Short-chain fatty acids (SCFAs) are a class of fatty acids that your gut microbes produce as they digest foods that your small intestine cannot digest. These compounds exert many beneficial effects on your body that range from regulating gut inflammation to maintaining gut integrity. For the nervous system, SCFAs act on enteroendocrine cells, a subset of cells in your gut that produces two peptides called glucagon-like peptide-1 (GLP-1) and peptide Y.Y. (PYY). GLP-1 and PYY act on your brain to make you feel full after eating a meal. 
  
• Neurotransmitter production: The bacteria living in your large intestines also produce molecules that impact how your nervous system behaves. These compounds, called neurotransmitters, act as chemical messengers that carry signals along the nerves that mediate your body’s movement and daily activity. Multiple bacterial species can produce neurotransmitters in your gut, such as Bifidobacterium species with gamma-aminobutyric acid (GABA) and Lactobacillus species with histamine, GABA, and serotonin. Neurotransmitters such as these diffuse from the gut to the enteric nerves, which then impact feelings of fullness and satisfaction from the brain.
  
• Induction of inflammation: Multiple factors can shape the structure and function of the gut microbiome, including medications taken and age. However, a person’s diet continues to play a critical role in the gut microbiome and health. For one, not taking care of the bacteria living in your gut can drive inflammation in your gut. The Western diet — lacking in fiber and high in added sugars, saturated fats, and salt — induces a constant, low-grade inflammation.

Going beyond “intra-gut” functions, it is becoming increasingly clear that gut physiology also interacts with your brain functions. New research has begun to more specifically link the composition of your gut microbiomes with mental health indicators and outcomes:

• A 2021 systematic review assessed the impacts of the gut microbiome composition on anxiety- and depression-associated disorders. After assessing 26 eligible studies, 18 of which assessed case-control comparisons for patients with depression, the researchers found a higher abundance of proinflammatory bacteria (e.g., Enterobacteriaceae and Desulfovibrio) among people with a mental health disorder. The same study also identified a lower abundance of bacteria that tended to produce short-chain fatty acids such as Faecalibacterium.
  
• A 2022 systematic review examined 44 studies that compared healthy controls with patients diagnosed with major depressive disorder (MDD), bipolar disorder (BD), and schizophrenia (SZ). Like the 2021 study, the review determined that patients with a mental health condition had lower abundances of bacteria able to produce short-chain fatty acids. The study also observed a higher abundance of bacteria that broke down glutamate and GABA, two chemicals that may control brain activity.
  

Transforming your diet and supplementation into brain health

The detrimental effects of a poor diet on brain health raise the importance of incorporating healthy foods into the meals you eat. With that in mind, here are a few suggestions you can take toward maintaining your cognitive function and mental health:

• Eat less highly processed foods: Highly processed foods contain a high concentration of fats, sugars, and digestible starch. Each of these compounds contributes to a high Glycemic Index (GI) value that increases the risk of type 2 diabetes (T2D). The insulin dysregulation observed among diabetics also impacts the brain, affecting mood and driving brain inflammation. Each of these mechanisms may explain the increased risk of all-cause premature preventable deaths in Brazil among those who ate more highly processed foods, in a study just published this month.To minimize the risk of adverse mental health problems, eat more whole and natural foods during your meals — and avoid packaged deli meats, white bread and sugar-sweetened cereals, hot dogs, cookies and similarly ultra-processed, high-sugar/fat food products.
  
• Incorporate more fish in your diet: Fish provides an excellent source of several nutrients essential for brain development and function. These include omega-3 fatty acids, proteins, and vitamins and minerals that can help protect against neurodegenerative disease and support mental health.
  
• Increase fruit intake: It may be tempting to fulfill your sweet tooth with a dessert that contains added sugars, but many sweet, fruity alternatives exist as well — providing myriad health benefits. Replace the snacks you eat with a fruit bowl and consider topping it off with savory nuts, which provide additional health benefits.
  
• Exercise more often: Exercise keeps your muscles strong and your cardiovascular system healthier. At the mental level, exercise also reduces blood sugar levels, thereby reducing the risk of inflammation in your brain. Even taking regular walks can boost your creativity, possibly by activating the parts of the brain that mediate higher cognitive functions.
  
• Consider trying a probiotic: Probiotics are microbes that provide a health benefit when ingested in sufficient quantities. Most probiotics are derived from fermented foods, but companies have made efforts to isolate and develop them specifically (as supplements) for enhancing your well-being. We recommend using Eden's daily synbiotic supplement, a 3-in-1 prebiotic, probiotic, and polyphenol superblend.

Key takeaways

When it comes to diet and mental health, what you eat plays a substantial role not only in your physical, but also your mental health. Veering off of a healthy diet increases the risk of mental disorders such as depression and anxiety. Eating a high-sugar, high-fat diet also increases inflammation in the brain, impairing brain activity and increasing the risk of cognitive decline. While elevated blood sugar levels play a role in these outcomes, the gut-brain axis — mediated by the microbes that live in your gut — also impacts your mental health. What you eat impacts how your microbes behave and in turn how your body reacts. Thus, keeping your gut and brain healthy requires a consistent habit of healthy eating and exercising. Doing so will help you keep your brain sharp and healthy for many years to come.