The connection between nutritional deficiencies and physical illness is well documented. But, did you know that there may be a connection between what you eat and how you feel mentally? Lifestyle factors such as lack of sleep, inactivity, and stress can lead to irritability and affect your mood. However, what you eat may also play a role.
An emerging area of science uses nutrition to enhance brain health. Known as Nutritional Psychology or Nutritional Psychiatry, this area of science recognizes the many roles that nutrients play when it comes to mood, behavior, and overall brain health. Nutrients allow chemical reactions to occur, support the function of cells and their ability to produce energy, reduce inflammation, and help with detoxification or removal of what the body does not want. Approximately 20-40% of the nutrients and energy we consume is used by the brain. When we eat, we are also feeding our brain [i].
The Connection Between the Gut and the Brain
From bite to brain: The quality of the food we eat directly and indirectly affects our brain and behavior. To function properly, the brain relies on appropriate nutrients, including lipids, amino acids, vitamins, and minerals, which we derive from food [ii]. Once food is digested and absorbed in the gastrointestinal tract, these nutrients eventually reach the brain. The array of food we eat also indirectly affects the brain through alterations in the trillions of bacteria colonized in the gut, the microbiota. These alterations include changes in the microbial composition, diversity, and activity of the gut. The brain’s capacity to regulate appetite and energy levels, for example, relies on certain metabolites (short chain fatty acids) produced by gut microbes [iii].
Playing telephone: Through bidirectional communication channels and multiple feedback loops known as the gut-brain-axis, the gut and its microbiome talk to the brain, particularly the cognitive and emotional centers of the brain, and the brain talks to the gut and its microbiome [iv]. Although not yet well understood, evidence suggests that interactions between the gut and brain occur through the vagus nerve, circulating blood levels, and the immune system. For example, neurotransmitters are chemical messengers produced in the gut that can transmit sensory signals through the vagus nerve to the brain and affect its function, including movement, emotion, learning, and memory. Reduced levels of some of these neurotransmitters are associated with symptoms of depression [v]. Precursors to neurotransmitters, like serotonin (associated with sleep, appetite, pain, and mood) and dopamine (associated with depression), are also produced by gut microbiota and travel through the blood to the brain. Once they arrive and accumulate in the brain, these precursors are transported across the blood-brain-barrier and taken up by neurotransmitter-producing cells where they then affect cognition and emotion. We obtain these precursors from our foods; the amino acid tryptophan (found in turkey and dark leafy greens) is a precursor to serotonin and the amino acid tyrosine (found in soy, peanuts, fish, and milk) is a precursor to dopamine. When there is a balanced gut microbiota, these amino acids can be metabolized and play their role in affecting the brain [v].
Trouble in the gut: When there is an imbalance in gut microbiota (or dysbiosis), various neurological disorders, including major depressive disorder, symptoms of depression, anxiety, mood, memory, and indicators of reduced quality of life can occur [iii]. In other words, the presence or absence of certain microbes can be brain altering. While advances in DNA sequencing and other technologies including the use of fecal transplantation, prebiotics, and probiotics continue to reveal the links among gut microbiota, the brain, and effects on mood and behavior, one thing is for sure: what you eat matters.
What to eat: Studies show that certain diets are associated with lower likelihood of developing depression. These include the Norwegian and Mediterranean diets which are characterized by a high intake of fruits, vegetables, whole grains, fish and lean meats [vi]. Additional foods like olive oil, low-fat dairy, and those with antioxidants are also associated with lower risk of depression [vii]. In one study of both male and female adults, self-reported levels of anxiety, stress, and well-being improved when a dietary pattern similar to the Mediterranean diet was followed regardless of BMI and lifestyle factors (physical activity, alcohol, and smoking), and the risk of depressive symptoms was highest among women who ate a pro-inflammatory diet [vi]. Similar to the Mediterranean diet, a plant-based diet was associated with positive changes in gut microbial composition and supports cognition [iv]. In one literature review of approximately 13 studies, a diet rich in fruits and vegetables was associated with self-reported increased life satisfaction, happiness, lowered stress, improved mood, and well-being, with vegetables having the greatest influence on total eating happiness [viii]. The DASH diet, characterized by a high intake of plant proteins, fruits, vegetables, low-fat dairy and restricted amounts of sodium, red meat, sweets, and sugar-sweetened beverages, is associated with improving symptoms of anger, depression, anxiety, tension, and vigor [ix]. A vegan diet may improve tension, depression, anger, fatigue, stress, and anxiety [ix]. On the other hand, a diet similar to the Western diet, characterized by a high intake of energy-dense, high-fat, high-sugar products, red and/or processed meat, refined grains, high-fat dairy products, butter, potatoes, high-fat gravy, and alcohol with low intake of fruits and vegetables, is associated with an increased risk of depression [vi]. The latter was also concluded in a meta-analysis of 21 cross-sectional and cohort studies from 10 countries, although not all studies adjusted for lifestyle behavior and environmental stressors [vii].
Inflammation: One possible link between diet and poor mental health and well-being is the inflammatory effect that certain foods may have on one’s body. The gut microbiome can trigger pro- and anti-inflammatory immune responses and inflammation in the brain [iv]. Chronic inflammation (elevated biomarkers of immune activity in the blood) is associated with depression and other mental disorders [x]. In one study of more than 40,000 women ages 50-77 followed over 12 years, those who ate a diet high in sugar-sweetened soft drinks, refined grains, red meat, diet soft drinks, and margarine (inflammatory foods), and low in red wine, caffeinated coffee, olive oil, and green leafy and yellow vegetables (protective foods) showed a greater risk of depression than those who ate a diet low in inflammatory foods and high in protective foods [xi].
Ultra-processed foods: Perhaps the greatest source of inflammatory foods for most Americans is highly processed foods known as ultra-processed foods. Ultra-processed foods are foods that are low-priced, shelf-stable, highly palatable (high fat, high sugar), industrial formulations derived from food combined with artificial additives such as preservatives, fillers, and dyes [xii]. A greater intake of ultra-processed foods is associated with greater odds of depressive and anxiety symptoms, trauma, and stress [xii]. When high amounts of sugar are consumed, free radicals and pro-inflammatory substances in the gut may be produced [ix]. A dietary pattern high in calories, saturated fat, and sodium may increase negative moods [ix, xiii]. In one study over a 5-year period, individuals ingesting the highest amounts of ultra-processed foods were significantly more likely to report mild depression, mentally unhealthy days, and anxious days per month [xiv].
Evidence suggests that emulsifiers, artificial food coloring, and other chemicals (eg. carboxymethylcellulose, polysorbate-80) alter the gut microbiota thereby fostering the body’s inflammatory response [xii]. Exposure to BPA used in plastic packaging may impact stress hormones and lead to anxious and depressive states, while certain artificial sweeteners (saccharine, aspartame) and MSG (monosodium glutamate) may affect neurotransmitters that regulate mood [xii].
Feelings derived from stress can influence appetite-related hormones (eg. cortisol) in our body and alter eating behavior. Emotional eating and comfort foods like ultra-processed foods are often sought in times of stress. Both the change in microbiota and hormones raise the desire for hyper-palatable foods leading to a higher risk of depression and other mood changes [vi, xii]. Eating ultra-processed foods such as potato chips once in a while may not be harmful, but a diet where ultra-processed foods become a staple may be.
While following an existing dietary pattern may be useful to improve mood, understanding the basis behind eating healthy diets may prove helpful. Deficiencies in certain vitamins, minerals, and additional nutrients are associated with serious cognitive and mood problems [xv]. The extent to which mild deficiencies also impact cognition and mood are still being researched, but here’s what we know:
- Vitamin B-12 and other B vitamins play roles in producing brain chemicals that affect mood and other brain functions, including cognitive function. Low levels of B-12 and other B vitamins such as vitamin B-6 and folate may be linked to depression [xvi]. A deficiency in B-12 is also associated with fatigue and lethargy [ii]. Vitamin B-12 is plentiful in animal products such as fish, lean meat, poultry, eggs, and low-fat and fat-free milk. If necessary, fortified breakfast cereals (unsweetened preferably) are also a good source of B-12 and other B vitamins [xv]. Reach out to Ina for good food sources of all B vitamins.
- Omega 3 fatty acids are needed for overall brain and nervous system functioning. They are essential in that our body does not produce them and they must be consumed in our diet. Omega 3 fatty acids can be found in fish, such as salmon, tuna, and halibut, other seafood including algae and krill, some plants, and seed and nut oils such as flax, chia, sunflower, soybean, and walnuts. Diets high in omega 3 fatty acids can reduce inflammation and improve mood [ix]. The Academy of Nutrition and Dietetics recommends fish be eaten at least twice per week by children and adults [xv].
- Magnesium inhibits inflammation. A low vegetable and whole grain diet is associated with low magnesium intake. Along with obesity, a diet deficient in magnesium has been associated with elevated inflammatory biomarkers in children [xv]. A Mediterranean Diet is high in magnesium and the link between a Mediterranean Diet and improved mood may be due to its high magnesium content [ix]. Foods high in magnesium include chlorophyll-rich vegetables, nuts, seeds, fatty fish like salmon and halibut, and whole grains.
- Vitamin D has many roles and contains anti-inflammatory properties. A deficiency in Vitamin D is associated with symptoms of depression and negative emotions [xvii]. Vitamin D can be obtained from sunlight (skin exposed to UV light produces Vitamin D) and diet. Foods high in Vitamin D include fatty fish, fish eggs or caviar, organ meats, egg yolks, and mushrooms.
- Protein is instrumental in repairing and building body tissues and can affect brain development, function, and physical and mental health. Many neurotransmitters in the brain are made from the amino acids in protein. A diet deficient in the amino acids tyrosine (used to make dopamine) and tryptophan (used to make serotonin) is associated with low mood and aggression [xviii]. Choose foods rich in lean, high quality protein such as meats, poultry, milk, other dairy products, eggs, and dark leafy vegetables. It is suggested that a plant-based diet rich in a variety of protein-rich foods like nuts, seeds, and legumes should provide adequate protein coverage, subject to individual needs [xix].
- Foods containing probiotics and foods serving as prebiotics may help the gut in its communication with the nervous system by maintaining a balance of good bacteria. As mentioned above, these bacteria and their by-products influence brain function and behavior. Discuss with your doctor and registered dietitian the possibility of supplementing with pre and probiotics. Supplementation of probiotics in older adults improved mental flexibility and reduced stress [xx]. Foods containing probiotics include plain yogurt, kefir, kimchi, kombucha, and sauerkraut. Prebiotics serve as food for the microbiota. Foods that act as prebiotics include asparagus, garlic, onions, walnuts, bananas, oats, apples, leeks, chickpeas, and lentils.
- Additional nutrients associated with depression or mood status are deficiencies in iron, iodine, chromium, selenium, zinc [xviii], vitamins C and E, phytochemicals and other antioxidants [ix]. Each of these nutrients is required for proper coordination, communication, and functioning within the body and nervous system. Ina can help you explore foods containing these nutrients.
What does all this mean?
Even though eating ultra-processed foods may make you feel good in the short term, in the long run it may not. As scientific researchers continue to work towards identifying the role and causal mechanisms that diet may have on mood, it is clear that an imbalanced gut flora and nutritional deficiencies can affect mental health. What foods will you choose for your next meal?
- Eat a diet rich in nutrient dense, whole foods such as the Mediterranean and DASH diets.
- Include foods containing antioxidant and anti-inflammatory properties such as salmon, kale, garlic, wild rice, and blueberries.
- Eat a rainbow of fruits and vegetables daily. The fiber in them is associated with improved brain health and function [iv].
- Ultra-processed foods containing sugar and fat can induce bloating, sluggishness, and promote negative feelings.
- Choose extra virgin oil for your salads. Extra virgin olive oil in particular has phenolic compounds that has anti-inflammatory properties [xxi].
- It is never too late to change your gut microbiota. Major diet changes in adulthood can modify the microbiota in just days [iii].
- Stress may cause increased gut permeability or leaky gut and inflammation which is implicated in chronic depression [xx]. If stressed, avoid the habit of reaching for sugar-ladened food providing a quick energy boost. Fluctuations in blood glucose can cause distinct changes in mood. Reach for fruits or vegetables (which are anti-inflammatory) with a healthy protein and/or fat to stabilize blood sugar levels.
- Focusing on what’s going well in your day instead of what’s going wrong may improve your health. Studies show that positive emotions can help deal with stress and improve energy [xxiii], and may help make better food choices.
- Look for interventions to reduce stress. Studies show that stress can reduce levels of micronutrients in your body [xxiv]. It may also affect the balance of good and bad bacteria in your gut, leading to more stress [xxv]. Try a 30 second body scan to relieve stress or mindful diaphragmatic breathing.
- Be mindful when you eat. Mindfulness eating is associated with improved mood, promotes awareness of satiety cues, and may help us make healthy snack choices [xxvi]. So, savor your food (its smell, taste, texture), consider the effort it took to grow, its connection to nature, and make healthy choices. It just might improve your mood!
As you consider the impact that diet, inflammation, and nutrient deficiencies may have on your mood, remember to reach out to your medical provider if you are experiencing any mental health issues. Taking care of your mental health is equally as important as taking care of your physical health and critical to optimizing overall well-being.
[i] Rucklidge JJ, Johnstone JM, Kaplan BJ. Nutrition Provides the Essential Foundation for Optimizing Mental Health. Evid Based Pract Child Adolesc Ment Health. 2021; 6:1, 131-154, doi: 10.1080/23794925.2021.1875342
[ii] Adan RAH, van der Beek EM, Buitelaar JK, Cryan JF, Hebebrand J, Higgs S, Schellekens H, Dickson SL. Nutritional psychiatry: Towards improving mental health by what you eat. Eur Neuropsychopharmacol. 2019 Dec;29(12):1321-1332. doi: 10.1016/j.euroneuro.2019.10.011
[iii] Oriach CS, Robertson RC, Stanton C, Cryan JF, Dinan TG. Foor for thought: The role of nutrition in the microbiota-gut-brain axis. Clin Nutr Exper. 2015; 6:25-38 doi:10.1016/j.yclnex.2016.01.003
[iv] Horn J, Mayer DE, Chen S, Mayer EA. Role of diet and its effects on the gut microbiome in the pathophysiology of mental disorders. Transl Psychiatry. 2022 Apr 20;12(1):164. doi: 10.1038/s41398-022-01922-0
[v] Chen Y, Xu J, Chen Y. Regulation of Neurotransmitters by the Gut Microbiota and Effects on Cognition in Neurological Disorders. Nutrients. 2021 Jun 19;13(6):2099. doi: 10.3390/nu13062099
[vi] Phillips CM, Shivappa N, Hebert JR, Perry IJ. Dietary Inflammatory index and mental health: A cross-sectional analysis of the relationship with depressive symptoms, anxiety and well-being in adults. Clin Nutr. 2017:1-7. doi: 10.1016/j.clnu.2017.08.029
[vii] Li Y, Lv MR, Wei YJ, Sun L, Zhang JX, Zhang HG, Li B. Dietary patterns and depression risk: A meta-analysis. Psychiatry Res. 2017 Jul;253:373-382. doi: 10.1016/j.psychres.2017.04.020
[viii] AlAmmar WA, Albeesh FH, Khattab RY. Food and Mood: The Corresponsive Effect. Curr Nutr Rep. 2020 Sep;9(3):296-308. doi: 10.1007/s13668-020-00331-3
[ix] Arab A, Mehrabani S, Moradi S, Amani R. The association between diet and mood: A systematic review of current literature. Psychiatry Res. 2019 Jan;271:428-437. doi: 10.1016/j.psychres.2018.12.014
[x] Haapakoski R, Mathieu J, Ebmeier KP, Alenius H, Kivimäki M. Cumulative meta-analysis of interleukins 6 and 1β, tumour necrosis factor α and C-reactive protein in patients with major depressive disorder. Brain Behav Immun. 2015 Oct;49:206-15. doi: 10.1016/j.bbi.2015.06.001
[xi] Lucas M, Chocano-Bedoya P, Schulze MB, Mirzaei F, O’Reilly ÉJ, Okereke OI, Hu FB, Willett WC, Ascherio A. Inflammatory dietary pattern and risk of depression among women. Brain Behav Immun. 2014 Feb;36:46-53. doi: 10.1016/j.bbi.2013.09.014
[xii] Lane MM, Gamage E, Travica N, Dissanayaka T, Ashtree DN, Gauci S, Lotfaliany M, O’Neil A, Jacka FN, Marx W. Ultra-Processed Food Consumption and Mental Health: A Systematic Review and Meta-Analysis of Observational Studies. Nutrients. 2022;14(13):2568. doi: 10.3390/nu14132568
[xiii] Hendy HM. Which comes first in food-mood relationships, foods or moods? Appetite. 2011; 58: 771-775. doi:10.1016/j.appet.2011.11.014
[xiv]Hecht, E., Rabil, A., Martinez Steele, E., Abrams, G., Ware, D., Landy, D., & Hennekens, C. Cross-sectional examination of ultra-processed food consumption and adverse mental health symptoms. Pub Health Nutr. 2022; 1-10. doi:10.1017/S1368980022001586
[xv] Mahan LK, Raymond JL. Krause’s Food & The Nutrition Care Process. 14th ed. Elsevier Inc.; 2017.
[xvi] Grajek M, Krupa-Kotara K, Biatek-Dratwa A, et al. Nutrition and mental health: A review of current knowledge about the impact of diet on mental health. Front Nutr.2022. doi: 10.3389/fnut.2022.943998
[xvii] Guzek D, Kołota A, Lachowicz K, Skolmowska D, Stachoń M, Głąbska D. Association between Vitamin D Supplementation and Mental Health in Healthy Adults: A Systematic Review. J Clin Med. 2021 Nov 3;10(21):5156. doi: 10.3390/jcm10215156
[xviii] Rao TS, Asha MR, Ramesh BN, Rao KS. Understanding nutrition, depression and mental illnesses. Indian J Psychiatry. 2008 Apr;50(2):77-82. doi: 10.4103/0019-5545.42391
[xix] Mariotti F, Gardner CD. Dietary Protein and Amino Acids in Vegetarian Diets-A Review. Nutrients. 2019 Nov 4;11(11):2661. doi: 10.3390/nu11112661
[xx] Kim CS, Cha L, Sim M, Jung S, Chun WY, Baik HW, Shin DM. Probiotic Supplementation Improves Cognitive Function and Mood with Changes in Gut Microbiota in Community-Dwelling Older Adults: A Randomized, Double-Blind, Placebo-Controlled, Multicenter Trial. J Gerontol A Biol Sci Med Sci. 2021 Jan 1;76(1):32-40. doi: 10.1093/gerona/glaa090
[xxi] Cicerale S, Lucas LJ, Keast RS. Antimicrobial, antioxidant and anti-inflammatory phenolic activities in extra virgin olive oil. Curr Opin Biotechnol. 2012;23:129–135. doi: 10.1016/j.copbio.2011.09.006
[xxii] Maes M, Kubera M, Leunis JC, Berk M. Increased IgA and IgM responses against gut commensals in chronic depression: further evidence for increased bacterial translocation or leaky gut. J Affect Disord. 2012 Dec 1;141(1):55-62. doi: 10.1016/j.jad.2012.02.023
[xxiii] Frederickson BL, Cohn MA, Coffey KA, Perk J, Finkel AM. Open Hearts Build Lives: Positive Emotions, Induced Through Loving-Kindness Meditation, Build Consequential Personal Resources. J Pers Soc Psychol. 2008;95(5):1045-1062. doi:10.1037/a0013262
[xxiv] Lopresti AL. The effects of psychological and environmental stress on micronutrient concentrations in the body: A review of the evidence. Adv. Nutr. 2020;1(11):103-112. doi:10.1093/advances/nmz082
[xxv] Madison A, Kiecolt-Glasser JK. Stress, depression, diet, and the gut microbiota: human-bacteria interactions at the core of psychoneuroimmunology and nutrition. Curr Opin Behav Sci. 2019; 28:105-110. doi:10.1016/j.cobeha.2019.01.011
[xxvi] Hsu T, Forestell CA. Mindfulness, mood, and food: The mediating role of positive affect. Appetite. 2021 Mar 1;158:105001. doi: 10.1016/j.appet.2020.105001