Nutrition and Mental Health: What’s the Connection?

While the media is making an effort to raise awareness of mental illness, the discussion is primarily focused on reducing the stigma around mental illness and the drugs and therapy used to treat it, rather than on interventions that address underlying causes of poor mental health. (4)

In the mainstream dialogue, discussion about the impact of nutrition on mental health is virtually absent. On the rare occasions when it is brought up, it’s often treated as a “profound” concept! (5) In all honesty, nutrition should be one of the first things brought up in the discussion about mental health due to its far-reaching impacts on the body and mind. Read on to learn about how the connection between nutrition and mental health and how a personalized, ancestral approach to food can help you restore a healthy body and mind. 

Nutrition has far-reaching impacts on the health of your body and your mind. Check out this article to find out how nutrition is linked with mental well-being, and learn 11 factors that influence your mental health. #nutrition #functionalmedicine #wellness

The Gut–Brain Axis and Mental Health

The relationship between nutrition and mental health is mediated by an influential structure within our bodies called the gut–brain axis. The gut–brain axis is a bidirectional communication network between the central nervous system (which is comprised of the brain and spinal cord), the enteric nervous system of the gut, and our gut microbes. The gut–brain axis also intersects with branches of the endocrine and immune systems, enhancing the complexity of this elegant system.

Signaling molecules created by gut microbes and cells of your intestine send messages to your brain along the gut–brain axis, influencing your mental and emotional functions. Signals also travel in the opposite direction, such that our mental and emotional states affect our gut function. Given the fascinating connections between the gut and brain, it should come as no surprise that the foods we eat ultimately impact our mental health.

Microbial Molecules Impact Mental Health

How exactly do our gut microbes communicate with our brains via the gut–brain axis? Research has revealed that gut microbes produce a variety of compounds that modulate brain function, including: (6)

• Neurotransmitters such as gamma aminobutyric acid (GABA), serotonin, norepinephrine, and dopamine
• Short-chain fatty acids, including butyrate and propionate
• Indoles, compounds derived from the amino acid tryptophan that have anxiety-promoting properties
• Bile acids
• Choline metabolites
• Lactate
• Vitamins including biotin and B12

After these metabolites are produced by gut microbes, there are three pathways by which they ultimately interact with the brain to modulate emotional behavior: (7)

1. Microbial metabolites activate fibers of the vagus nerve that originate in the gut and connect the gut to the brain.
2. Microbial metabolites stimulate the immune system within the gut and circulating immune cells in the blood upon entering the systemic circulation.
3. Microbial metabolites can be directly absorbed into the bloodstream and interact with other organs, including the brain.

Inflammation Intersects with the Gut–Brain Axis

These metabolites also interact with components of the immune system, including the gut-associated lymphoid tissue (GALT) in the gastrointestinal tract. This interaction helps to explain the link between immune dysfunction, chronic inflammation, and mental illness. (8)

Fortunately, we have a powerful tool available for modulating inflammation, gut health, and mental health: nutrition! While the relationship between food and mental health begins very early in life, as I’ll discuss next, it is never too late to improve your diet and your mental well-being.

Early-Life Nutrition Shapes Mental Health

The relationship between nutrition and mental health begins very early in life—in fact, it starts before birth. The fetal brain is highly sensitive to nutrient deficiencies due to its extreme plasticity, or its sensitivity to environmental inputs capable of altering its structure and function.

Research indicates that parental nutritional status plays a critical role in shaping an infant’s developing brain and future risk of mental health disorders. In preclinical studies, paternal deficiency of methyl-donor nutrients—choline, folate, and methionine—has been found to increase the risk of anxious and depressive behaviors in offspring by altering gene expression in sperm cells. (9) Maternal preconception nutrition status also has a significant impact, with maternal deficiencies of folate and choline significantly increasing the risk of childhood neurodevelopmental disorders. (10) Conversely, maternal intake of excess folic acid before and during pregnancy may have adverse effects on children’s mental health. (11)

After birth, an infant’s brain remains highly sensitive to nutritional inputs. The first 1,000 days of a child’s life represent a critical time window for optimizing nutrition and brain development. (12) Breastfeeding reduces the risk of mental health disorders in childhood by seeding the infant gut with beneficial bacteria and providing nutrients that support gut and brain development. Protein and micronutrient deficiencies in infancy epigenetically alter cognitive development, and may predispose the infant to mental health disorders down the road. (13, 14)

11 Nutritional Factors That Influence Mental Health

After birth and throughout the lifespan, a variety of dietary factors coalesce to impact mental health. These factors include:

• The standard American diet
• Gut dysbiosis
• Blood sugar dysregulation
• Inflammatory dietary triggers such as gluten
• Vitamin and mineral deficiencies

Conversely, nutritional components such as probiotics, prebiotics, essential fatty acids, and phytonutrients have protective effects on mental health.

1. The Standard American Diet

A growing body of epidemiological research links the consumption of a processed, refined Western diet with psychological disorders, including depression and anxiety. (15, 16) While reverse causation cannot be ruled out—people with poor mental health may be more likely to make unhealthy food choices—there are several plausible mechanisms by which a Western diet (aka the “standard American diet, or SAD”) may adversely impact mental health:

• It promotes a pro-inflammatory gut microbiome, which induces gut–brain axis dysfunction.
• It promotes deficiencies of nutrients that support optimal mental health, including omega-3 fatty acids and magnesium.
• It increases intestinal permeability, which is linked to anxiety and depression. (17) Zonulin, a protein increased in leaky gut, is involved in both gut barrier and blood–brain barrier disorders.

The SAD is a recipe for poor mental health, according to a growing body of research. Ultra-processed food consumption is linked to an increased risk of mental health disorders. (18)

Several components of the SAD disrupt the gut microbiota, which, in turn, affects mental health via the gut–brain axis. Carboxymethylcellulose and polysorbate 80, emulsifiers found in many processed foods, promote anxiety by triggering gut inflammation. Acellular carbohydrates promote a pro-inflammatory gut microbiome, which may, in turn, induce brain inflammation. (19, 20) Chronic stress exacerbates the harmful mental health effects of a Western diet by altering the omega-6/omega-3 fatty acid ratio in neuronal cell membranes, impairing neurotransmission. (21)

A higher dietary inflammatory index, a measure of the overall inflammatory potential of a diet, is associated with schizophrenia. (22) Given these findings, food should not be an afterthought in the treatment of mental health issues, but rather should be at the forefront of treatment.

2. An Ancestral Diet

In contrast to the SAD, traditional dietary patterns have been found to support robust mental health. (23)

For optimal mental health, I recommend that my clients eat a diet centered around the following foods:

• Non-starchy vegetables—at least three or four servings a day, unless contraindicated by gut issues
• Whole fruits
• Meat, poultry, seafood, and eggs
• Moderate amounts of starchy vegetables such as sweet potatoes, winter squash, and plantains
• Nuts and seeds
• Properly prepared grains and legumes, if tolerated
• Full-fat dairy, if tolerated

This well-rounded dietary template provides all the nutrients required by the body to support a healthy brain and balanced mental health.

3. Gut Dysbiosis

Fascinating research indicates that mammalian brain cells evolved in the colon, suggesting that our guts may, in fact, be our “first brains!” (24) Multiple lines of evidence indicate that gut dysbiosis influences the course of many mental health disorders.

Gut microbes produce an astounding array of metabolites that send messages to the brain, ultimately modulating cognition, emotions, and behavior. When the gut microbiota are compromised by factors such as antibiotics and processed foods, aberrant microbial signaling may result, contributing to mental health issues such as:

• Depression (25, 26)
• Anxiety (27)
• Bipolar disorder (28)
• Schizophrenia (29)
• Anorexia nervosa (30)

Several antidepressants and antipsychotics have been found to disrupt the gut microbiota, instigating a vicious cycle of dysbiosis and poor mental health. Fluoxetine, a selective serotonin reuptake inhibitor (SSRI), decreases anti-inflammatory bacterial species such as Lactobacillus johnsonii and Bacteroidales S24-7 while increasing dysbiotic bacteria and anxiety-like behavior in mice. (31) Lactobacilli may be adversely impacted by SSRIs due to the presence of biogenic amine transporters in their cell membranes, which enable them to inadvertently take up fluoxetine, a drug that appears to have toxic effects on them. Atypical antipsychotics, a class of drugs commonly used in people with bipolar disorder, may also trigger gut dysbiosis by decreasing gut microbial diversity. (32, 33)

Similarly, depletion of the gut microbiota by antibiotics has been found to induce anxiety and depression-related behaviors in mice by altering the availability of serotonin, a neurotransmitter that is made in significant quantities by commensal gut microbes. (34)

4. Blood Sugar Control

Blood sugar management is probably not the first thing (or even the second or third thing) that comes to mind when most people think about mental illness. However, a growing body of research indicates that dysglycemia is a crucial feature in mental health disorders.

In people with type 1 and type 2 diabetes, the degree of hyperglycemia is positively associated with the risk of depression. Poor blood sugar control may harm mental health by increasing gut and brain inflammation, thus compromising mental health. (35, 36) Insulin resistance in the brain may facilitate mood disorders by increasing the clearance of dopamine, a neurotransmitter that is frequently decreased in depression. (37)

Interestingly, antidepressant treatment may improve glycemic control in the short term, but worsen it in the long term, increasing an individual’s risk of prediabetes and diabetes, which, as I mentioned earlier, can impact mental health. (38)

5. Gluten

Mental health issues are common comorbidities in celiac disease and non-celiac gluten sensitivity (NCGS). (39) Gluten antibodies are elevated in people with bipolar disorder, major depression disorder, and schizophrenia. (40) Adherence to a gluten-free diet is associated with reduced depressive symptoms in people with celiac disease and NCGS as well as improved psychotic symptoms in patients with schizophrenia. (41, 42) Furthermore, a blinded gluten challenge after a gluten-free diet led to a return of depressive symptoms in individuals with NCGS. (43)

Gluten may impair mental health by increasing intestinal permeability, causing an escape of pro-inflammatory metabolites into the systemic circulation. Once in circulation, these metabolites travel to the brain, triggering an inflammatory response and neuropsychiatric problems.

6. Minerals

A handful of minerals are essential for mental health, due to their roles as cofactors for neurotransmitter-producing enzymes and their effects on neurogenesis.

Iron

Iron deficiency is known to impair the development of the human brain. (44) However, iron deficiency is also associated with an elevated risk of depression, anxiety, bipolar disorder, and attention-deficit/hyperactivity disorder (ADHD) in children and adolescents. (45) Iron deficiency may promote mood disorders by impairing the production of serotonin, dopamine, and norepinephrine.

Heme iron is the most bioavailable form of dietary iron, and it is found exclusively in meat, poultry, and seafood. Non-heme iron, found in plant foods such as spinach and whole grains, is far less bioavailable. Iron insufficiency and iron deficiency are common in vegans and vegetarians, and may explain why people on such diets frequently experience declines in mental health over the long term. (46)

Zinc

Zinc is an essential trace mineral second only to iron in abundance in the body. It is present in high concentrations in regions of the brain associated with emotional processing, including the hippocampus and frontal cortex. Zinc deficiency has adverse effects on mood. (47)

In clinical trials, supplemental zinc has been found to work synergistically with SSRIs to significantly reduce depression severity in major depressive disorder. (48) Zinc may improve depressive symptoms by increasing brain plasticity, balancing excitatory and inhibitory neurotransmission, and reducing the production of inflammatory cytokines. (49, 50)

Magnesium

Magnesium is the premier “calming mineral,” and it can do wonders for reducing anxiety and boosting mood. Magnesium supplementation has been found to reduce subjective anxiety and stress, and improves mild-to-moderate depression in adults. (51, 52)

Magnesium is a cofactor for enzymes involved in the degradation of norepinephrine and epinephrine, and is an antagonist at excitatory N-methyl-D-aspartate receptor, or NMDA, channels in the brain. It thus helps reduce excitatory neurotransmission, allowing the brain to enter “rest and digest” mode.

7. Vitamins

Several vitamins have been identified as critical dietary components for good mental health, including:

• Folate
• Vitamin B12
• Vitamin B6
• Choline
• Vitamin C
• Vitamin D

Folate

Folate is a member of the B vitamin family found naturally in leafy greens, liver, and legumes. It is also present in a synthetic form, folic acid, in fortified and processed foods.

A large body of research indicates that impaired folate metabolism, mediated by variations in the methylenetetrahydrofolate reductase (MTHFR) enzyme, can impair mental health. MTHFR converts 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate (5-MTHF). 5-MTHF subsequently participates in reactions involved in neurotransmitter production. Two MTHFR variants—MTHFR C677T and A1298C—reduce 5-MTHF availability, downregulating downstream pathways involved in mental health. Variants in MTHFR C677T and A1298C are linked to depression, anxiety, bipolar disorder, schizophrenia, and ADHD. (53, 54)

Individuals with these variants may benefit from an increased intake of natural food sources of 5-MTHF and 5-MTHF supplementation. Supplemental L-methylfolate has been found to improve depressive symptoms. (55)

Vitamin B12

Vitamin B12 works synergistically with folate to support homocysteine metabolism, methylation, and healthy neurotransmission. (56) Vitamin B12 deficiency promotes:

• Cognitive decline
• Irritability
• Personality changes
• Depression
• Psychosis

B12 supplementation alleviates symptoms of major depressive disorder when taken in conjunction with antidepressants. (57)

Vitamin B12 is found almost exclusively in animal products, including meat, poultry, fish, eggs, and dairy products. Along with iron deficiency, B12 deficiency may contribute to mood disorders in vegetarians and vegans.

Vitamin B6

Vitamin B6 is a crucial cofactor for enzymes involved in the synthesis of serotonin, dopamine, and epinephrine. (58) Vitamin B6 deficiency thus reduces neurotransmitter synthesis and is linked to depression and anxiety. Vitamin B6 works synergistically with magnesium to alleviate stress in healthy adults. It also relieves premenstrual syndrome-related anxiety. (59, 60) Good food sources of vitamin B6 include:

• Pork
• Poultry
• Fish
• Eggs
• Avocado

Choline

Little research has been conducted on the relationship between choline and mental health disorders. However, choline is a crucial nutrient for healthy brain development in gestation and infancy, and a deficiency of choline during these critical developmental windows may increase a child’s future risk of neuropsychiatric disorders. (61) Pregnant women should ensure that they get at least 450 mg of choline per day, and lactating women should consume at least 550 mg per day, to promote optimal brain development and future mental health in their offspring.

The best food sources of choline are liver, egg yolks, and beef, chicken, and turkey muscle meats. Cruciferous vegetables provide smaller amounts of choline.

Vitamin C

In epidemiological studies, a higher vitamin C status is associated with elevated mood. (62) While this observation could simply be because healthier diets tend to contain more vitamin C and are associated with reduced depression, several lines of evidence suggest that vitamin C has direct benefits for mental health. Vitamin C’s antioxidant properties may protect neurons against oxidative stress, and they may have epigenetic effects on genes involved in mental health. (63) Vitamin C is abundant in:

• Citrus fruits
• Kiwi
• Strawberries
• Bell peppers
• Broccoli

Vitamin D

More and more evidence continues to accumulate demonstrating the importance of vitamin D for mental health. Vitamin D supplementation results in statistically significant improvements in depressive symptoms. (64)

I recommend sun exposure as a primary source of vitamin D; however, if you live above 37 degrees north latitude, your body will make little, if any, vitamin D between October and April. If you use sunscreen religiously in the summer, your total yearly vitamin D production will amount to even less. To learn how to make the most of the sun exposure available where you live, check out the dminder app, which tells you how much time you need to spend outdoors (and at what time of day) to make a given amount of vitamin D via your skin.

Wild-caught seafood and pastured egg yolks also supply bioavailable vitamin D, albeit in much smaller amounts than sun exposure. In people who simply can’t get enough vitamin D from the sun and food, a supplement may be necessary.

8. Fermented Foods, Probiotics, and Prebiotics

Gut health is an intrinsic component of mental health. Consuming the right types of probiotics can help us support our gut health and mental health. Scientific and clinical interest in probiotics with targeted effects on the brain has led to the creation of a new term, “psychobiotics,” which are defined as live bacteria that confer mental health benefits. (65)

What are some common examples of psychobiotics?

• Lactobacillus rhamnosus is a particularly promising psychobiotic. It produces GABA, a calming neurotransmitter, and has been found to reduce postpartum depression and anxiety. (66)
• Lactobacillus plantarum alleviates stress and anxiety while enhancing memory and cognition in stressed adults. (67)
• Lactobacillus helveticus downregulates hypothalamic–pituitary–adrenal (HPA) axis activity while Bifidobacterium longum decreases self-reported mental distress. (68)

Psychobiotics show such promise that several nutraceutical companies are now developing or offering psychobiotics formulations. One psychobiotic with which I’ve had success in my clinical nutrition practice is Klaire Labs Target gb-X.

When talking about probiotics and mental health, we can’t forget to include a discussion of prebiotics. Prebiotics are dietary fibers that can be fermented by gut bacteria. Fructooligosaccharides and galactooligosaccharides, two types of prebiotic fibers, alleviated depression and anxiety in mice by increasing the growth of anxiolytic gut bacteria. (69) Prebiotics also increase the production of brain-derived neurotrophic factor (BDNF), linked to reduced depressive symptoms, and promote bacterial output of short-chain fatty acids, which induce vagus nerve signaling. (70, 71) Vagus nerve stimulation via an implanted device is currently a U.S. Food and Drug Administration-approved treatment for depression. Prebiotic fibers may represent a far less invasive option for enhancing vagal nerve tone by stimulating bacterial production of short-chain fatty acids. (72)

9. Essential Fatty Acids

The essential omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) demonstrate multiple mental health benefits. While DHA is critical for brain development, EPA appears to be the most effective omega-3 fatty acid for supporting mental health. EPA supplementation reduces depressive symptoms and may also regulate impulsivity and aggression. (73, 74) The ideal dosage of EPA appears to be 1 to 2 grams per day or a ratio of 2:1 to 3:1 EPA to DHA. (75)

Omega-3 fatty acids may support mental health by maintaining the fluidity of neuronal cell membranes, thus facilitating seamless, healthy neurotransmission. EPA may alleviate neuroinflammation by competing with arachidonic acid for metabolism by desaturase enzymes, thus reducing the production of pro-inflammatory arachidonic acid metabolites. (76)

10. Phytonutrients

Phytonutrients are chemical compounds produced by plants that help the plants defend themselves against pests and survive harsh conditions such as drought. The consumption of phytonutrients places mild stress on our bodies, upregulating signaling pathways that increase our resilience to future stressors and support cognitive health. Phytonutrients may also increase neuroplasticity by enhancing the production of BDNF and enhance calming GABA neurotransmission.

• Curcumin, a phytochemical found in the golden root of the turmeric plant, has recently been found to exert antidepressant effects in subjects with major depressive disorder. (77)
• L-theanine, an amino acid derivative found in green tea, has anti-anxiety properties. (78)
• Glucoraphanin and its metabolite sulforaphane are widely distributed in cruciferous vegetables, and have been found to modulate depression by upregulating the nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant pathway and supporting neuronal plasticity. (79)
• Cocoa flavonoids alleviate stress and brain inflammation, as indicated by electroencephalogram measurements. People who report eating dark chocolate regularly also report significantly lower odds of depressive symptoms, suggesting that cocoa-flavonoid-rich dark chocolate (in moderation) may support mental health. (80, 81)

11. Coffee, Tea, and Caffeine

Dietary stimulants, namely caffeine, have varying effects on mental health depending on a person’s genetics and other individual lifestyle factors. Some studies suggest that coffee and tea have protective effects against depression, perhaps due to their content of polyphenols and, in the case of tea, L-theanine, a calming amino acid derivative. (82, 83)

To determine whether or not caffeine is conducive to your optimal mental health, there are several things you can do.

Do genetic testing to determine your CYP1A2 status. CYP1A2 is a gene that codes for a liver enzyme of the same name that is responsible for metabolizing caffeine. CYP1A2 has several variants. People with the CYP1A2 genotype AA are “fast metabolizers,” meaning their livers break down caffeine quickly, whereas the CYP1A2 AC and CC genotypes yield slow caffeine metabolism. (84) Slow metabolizers may be more likely to experience anxiety and insomnia from habitually drinking coffee and other high-caffeine beverages. In contrast, fast metabolizers may be able to drink multiple cups of coffee a day without a hitch. (85) You can learn about your caffeine metabolism genetics with a genetic test such as 23andMe.

While this testing may be helpful, other genes impact caffeine metabolism and are not yet included in genetic testing panels, so we shouldn’t obsess too much over the results of a single genetic marker for caffeine metabolism. The best way to assess the effects of coffee and other caffeine-rich beverages on your mental health is to observe how you feel when you consume these drinks. If you feel anxious after one cup of coffee, then you should probably not consume it regularly.

Plant-Based Diets and Mental Health

I’ve mentioned several mental health-supportive nutrients that tend to be low in vegetarians and vegans, including iron and vitamin B12. However, I think it is worth reiterating the potential hazards of vegetarian and vegan diets for mental health.

Diets that omit animal products, including meat, seafood, and eggs, run the risk of causing deficiencies in many nutrients that are crucial for mental health, including:

• Iron (86)
• Zinc (87)
• Choline (88)
• Vitamin D (89)
• Vitamin B12 (90)
• Vitamin B6 (91)
• Omega-3 fatty acids (92)

Perhaps not surprisingly, several studies link vegetarianism with depressive symptoms. (93, 94) Anecdotally, many vegetarians and vegans find that their depression and anxiety dissipate, and their moods stabilize upon reintroducing animal foods to their diets.

Mindful Eating: Tying Together Mental Health and Food

Mindful eating is a way of eating that involves bringing your attention and awareness into the present moment as you eat a meal. Our minds are continuously bombarded with cues from our external environment that trigger emotional eating and other maladaptive eating behaviors. People with pre-existing mental health issues are more likely to engage in emotional eating. Mindful eating halts the vicious cycle of emotional, mindless eating, and may help you better manage food cravings and support better mental health. (95, 96, 97) Mindful eating is thus a powerful tool to use alongside nutrition care for supporting mental health.

To eat mindfully, focus your attention on your experience of food when you are eating a meal. Avoid answering emails, texting, or watching TV while eating. Savor the flavors and textures of your food, and enjoy it in the company of family and friends, as much as possible.

While nutrition is essential for building optimal mental health, it is but one piece of the puzzle. Lifestyle factors such as sleep, stress management, and exercise are also critical contributors to mental health. Check out Chris’s articles on sleep, stress, and movement to learn more about how to fine-tune these aspects of your lifestyle and create a foundation for optimal mental health. 

Diet and lifestyle are the primary factors in health and disease, and adopting an ancestral approach can prevent or even reverse chronic illness and improve overall health. When that approach is combined with the support of a trained Functional health coach, it can change lives.

If you’re interested in making a living while making a difference in peoples’ lives and their health, a career as a Functional health coach could be the right next step for you—and the ADAPT Health Coach Training Program can help you start that journey. Find out more about health coaching and the ADAPT Health Coach Training Program.