How Diet Influences Your Brain and Mood — BrainPost | Easy-to-read summaries of the latest neuroscience publications

Brain-body connections that allow food to influence mood

Our moods and emotions govern our lived experiences and are inextricably linked to the function of our brains and bodies. Ingesting certain macro- and micronutrients through our diet can impact the chemicals in our brain that contribute to many emotional states, such as happiness, sleepiness, and sadness. Food choice has been strongly implicated in both mental and overall health and well-being. Gaining insight into how the nutrients that make up our food affect our brain and behaviour could help us understand how to improve our mental health and overall well-being through our dietary choices.

The role of the vagus nerve

One of the primary pathways through which the brain and body communicate is a bidirectional superhighway known as the vagus nerve. The vagus nerve is the 10th cranial nerve and the longest cranial nerve in the body– starting at the base of your neck, and innervating the brain as well as the organs of the body, including the heart, lungs, stomach, intestines, and liver. Through the vagus nerve, the brain receives information regarding the state of our organs, such as how distended our gut is, how full our intestines are, and how quickly our heart is beating. It can also send motor signals back to the organs, such as telling our heart or our guts to slow their pace. This nerve is one way in which the brain and body are connected and can integrate our emotional states, mood, and well-being.

Food and neurotransmitters

The production of neurotransmitters such as serotonin, dopamine, and norepinephrine relies on appropriate levels of critical building blocks that we receive from food, such as amino acids, fats, carbohydrates, and minerals. For example, the amino acid L-tyrosine, is a precursor to dopamine and norepinephrine, while both tryptophan (a different amino acid) and carbohydrate-rich foods increase the production of serotonin. Depending on the number of precursors present in the food you eat, you may produce more or less of a certain neurotransmitter. Importantly, imbalances in these neurotransmitters have been associated with numerous neuropsychiatric illnesses, and affect our mood and alertness.

Neurotransmitters are also released in anticipation of and in response to certain foods. For example, the locus coeruleus has been found to release norepinephrine to activate the lateral hypothalamus (the nucleus that regulates food intake) during food preparation. This increases alertness around food, which can lead to feelings of excitement, but also anxiety. Additionally, ingestion of certain foods can induce dopamine release, potentially leading to cravings that cause us to seek out more of that food. For example, certain neurons in the stomach will release dopamine in response to sugar. Interestingly, this is not related to the rewarding sweet flavor of sugary foods, but to specific sugar-sensing neurons in the gut; the same dopamine response occurs even if the sweet taste of sugar is masked. This indicates that there are certain circuits in the body that drive behaviour towards certain types of food based on information that comes directly from our bodies, and not necessarily from our cognitive appraisal of how much we “like” that food.

Brain-derived neurotrophic factor (BDNF) is an abundant signaling molecule intimately related to both cognitive function and metabolic regulation in the brain. BDNF is involved in reshaping synaptic connections in the context of learning and memory but also plays a role in energy mentalism, appetite suppression, and energy balance in the body. Importantly, low serum levels of BDNF have been identified in individuals with psychiatric diseases, such as schizophrenia and depression, and it is thought to be a key player in mediating the positive effects of antidepressants on the brain. Several studies have investigated the relationship between diet and BDNF and found that diets rich in polyphenols were associated with elevated levels of BDNF. Interestingly, these micronutrients may play a role in disease prevention and longevity as well.

Omega-3 fatty acids

Omega-3 fatty acids are an integral part of neuronal cell membranes and play a key role in several central nervous system functions including neurotransmission, gene expression, neurogenesis, and neuronal survival. These fatty acids can be found in fatty fish, eggs, flax seeds, hemp seeds, and chia seeds, and can also be ingested as supplements in capsule or liquid form.

If ingested in the correct ratios (i.e., high omega-3 relative to -6), these fatty acids may have antioxidant and anti-inflammatory properties. In one human study, a low dose (20 mg) of the antidepressant Prozac, a serotonin reuptake inhibitor, and a high dose (1000 mg) of EPA, an essential fatty acid high in omega-3, were found to have similar antidepressant effects. Taken together, the two compounds had synergistic effects, suggesting that the omega-3 fatty acids may amplify the effects of antidepressants. The shift in omega-3 to -6 ratio has been shown to lower inflammation in the body and increase heart rate variability, both of which may improve symptoms of depression and allow antidepressants to do their work.

Micronutrients such as B and D vitamins, zinc, and more

In addition to adequate levels of amino acids, carbohydrates, and fats, our brain, and body also rely on numerous minerals and micronutrients to function optimally. When we are nutritionally deficient in certain micronutrients such as vitamin B12, vitamin B9 (folate), vitamin D, or choline, we may experience symptoms like depression, low mood, fatigue, cognitive decline, and irritability. Similar results have been found for trace minerals such as calcium, zinc, copper, iron, and selenium. Often, diets high in processed food can put individuals at greater risk for nutritional deficiencies, increasing the likelihood of negative impacts on both mood and general cognitive function. Vitamin supplementation has been found to combat cognitive impairment and energy metabolism in both rodent and human studies.

Conclusions on diet and mental well-being

The nutrients within our food likely have profound effects on our brain and body, affecting both our health and how we feel. Prioritizing and promoting diets that are healthy for our brains may have important benefits for our daily lives. Furthermore, food is a critical component of cultural heritage and can connect us to family and friends, as well as places. Understanding how our mood and well-being are impacted by all these factors can help us to better understand and regulate our emotions and our overall health.

References +

Bremmer JD et al., Diet, Stress and Mental Health. Nutrients, 2020.

Gomez-Pinilla. Brain foods: the effects of nutrients on brain function. Nature Review Neuroscience, 2008.

Gravesteijn E et al., Effects of nutritional interventions on BDNF concentrations in humans: a systematic review. Nutritional Neuroscience, 2022.

Jazayeri S et al., Comparison of Therapeutic Effects of Omega-3 Fatty Acid Eicosapentaenoic Acid and Fluoxetine, Separately and in Combination, in Major Depressive Disorder. Australian & New Zealand Journal of Psychiatry, 2008.

Lachance L & Ramsey D. Food, Mood, and Brain Health: Implications for the Modern Clinician, Missouri Medicine, 2015.

Meeusen R & Decroi L. Nutritional Supplements and the Brain. Int J Sport Nutr Exerc Metab, 2008