What we put in our mouths directly impacts our mood, according to a new study, and understanding the connection between diet and mental health can help us make better food choices and experience less daily stress. The gut and the brain are constantly communicating with each other, via what's called "the gut-brain axis," and nutritional compounds in the food we eat can have a dramatic influence on our stress levels.

A new study that followed 300,000 people over nine years has found that people who eat more fruit and vegetables are less stressed than those who don't eat these healthy whole foods. The mood-boosting benefits of fruit and vegetables are just one more benefit of a plant-based diet, which has already been proven to help reduce the risk of heart disease, as well as type 2 diabetes, and even certain cancers (especially those cancers related to obesity), and other lifestyle conditions like high blood pressure.

American is experiencing a mental health crisis

More Americans than ever are experiencing mental health conditions such as stress, anxiety, and depression according to Mental Health America. The reporting of these conditions has "skyrocketed since 2019," with 93 percent reporting more anxiety and 62 percent reporting more depression since the pandemic began. While this is a multi-faceted problem, anything that an individual can do to improve their mental health is worth considering; one thing everyone has control over is what they eat.

A Gallop survey found that US and Canadian workers are among the most stressed in the world, ranking highest for daily stress levels of all groups surveyed: 57 percent of US and Canadian workers (the two are lumped together in this survey) reported feeling stress on a daily basis, up 8 percentage points from the prior year, according to the June 2021 report.

Unfortunately, when stressed, we often try to soothe ourselves by stress eating, and reach for the exact foods that will make our mental health situation worse, such as processed junk food and sugary snacks. Reaching for healthy foods such as fruits and vegetables has been proven to help mitigate those anxious or depressed feelings, according to past studies.

The latest evidence backs up the impact of food choices on our mental health. An extensive study examined the association between fruit and vegetable intake and mental health disorders. The data from nearly 300,000 Canadians over the age of 12 showed that increased fruit and vegetable intake was associated with less depression and other symptoms of psychological stress.

If certain foods help us to manage stress, it makes sense that we add them to our diets. However, many people don’t make the link between what they eat and their emotional health and their dietary choices, or even understand how food choices affect their mental health.

At the start of this year, the American Psychological Association conducted a Harris Poll that found that 84 percent of 2076 adults surveyed experienced emotions associated with prolonged stress. Participants cited the covid-19 pandemic, political unrest, and social divisiveness as contributing reasons.

Whether work-related stress, financial difficulties, or relationships, the unfortunate fact is that we live with ever-increasing numbers of stress, depression, anxiety, and suicide as a society.

What we eat impacts brain function, stress levels, and mental health

The connection between diet and mental health has been studied in the past but the new research from Canada shows a direct correlation between "greater [Fruit and Vegetable Intake, or] FVI was significantly associated with lower odds of depression" while the inverse was true: Those with  "perceived poor mental health status and previous diagnosis of a mood disorder and anxiety disorder" had the lowest intake of fruit and vegetables. The study was repeated over five waves of time and each time the researchers found the same results, confirming that the impact of our food choices on mental health is enormous.

The brain and gut are connected by a two-way system called the gut-brain axis which allows the brain to communicate with the gut and vice versa. The gut is sometimes referred to as ‘the second brain’ because it has millions of neurons (nerve cells) making up what’s called the enteric nervous system (ENS).

The gut-brain axis determines whether we are feeling stressed or relaxed. Through a complex system involving the hypothalamic-pituitary-adrenal (HPA) axis and the vagus nerve, our bodies activate one of two systems, the sympathetic response or parasympathetic response.

The sympathetic nervous system activates our stress response, or "fight or flight" response to stressors, whereas the parasympathetic nervous system tells our bodies to "rest and digest." Most of us have our fight or flight response switched on for long periods of time, creating havoc in our bodies, including the release of the stress hormone cortisol which tells the body to store fat for fuel to help us fight or evade the saber tooth tiger. Too often we’re in a constant state of hyper-stress, even when we’re simply working at our desk or stuck in traffic.

The gut-brain connection: What to eat for a healthy microbiome

Considering the gut-brain axis, it makes sense that what we put into our mouth ends up influencing our stress response. Eating healthy fruits and vegetables full of antioxidants, fiber and nutrients signals to the body and brain that all is well, that our cells are being replenished and nourished. An integral piece of this puzzle is the type of bacteria in our gut, also known as the microbiome since what we eat dictates the health and diversity of the trillions of microbes that inhabit the gut, and helps to determine not only our disease risk but mental health as well.

According to a 2019 review study, the microbiota-gut-brain axis is responsible for psychiatric, neurological, and neurodegenerative diseases. The authors indicate that the link between our gut, its bacteria, and the brain might influence our risk of depression, anxiety, eating disorders, and addiction.

Exactly what to eat to avoid stress or fight it when it hits

Once we understand the link between food and mood, we next need to consider what we should eat for our well-being. Often, when someone is stressed, they make poor food choices, either due to time constraints or comfort eating, which compounds the problem.

Switching to a plant-based diet could be the way forward, according to a new study that shows that people who eat more fruit and vegetables are less stressed.

The 2021 study published in Clinical Nutrition assessed dietary habits and stress levels among 8,689 Australian adults as part of the Australian Diabetes, Obesity, and Lifestyle (Study. The researchers found that participants with the highest intake of fruit and vegetables (at least 473 grams per day) had 10 percent less perceived stress than those with the lowest intake (243 grams a day or less).

Eat six to eight portions of fruit and vegetables a day

Fruit and vegetables contain an arsenal of beneficial nutrients to fight ill health, including vitamins, minerals, phytochemicals, and fiber. But just how much should we eat a day?

A standard serving in grams (g) is around 75g, so the most beneficial amount according to this study would equate to six or more servings per day.

The Dietary Guidelines for Americans recommend that people eat 2 to 4 cups a day of vegetables and 1½  to 2 cups of fruit per day, depending on someone’s age and sex. However,  research suggests increasing your fruit and vegetable intake to 8 servings a day can help reduce the risk of premature death and cardiovascular disease by up to 30 percent.

So the research indicates that to be your healthiest, physically and mentally, eat at least 6, and preferably 8 servings of fruit and vegetables a day. The ratio of how much fruit to vegetables favors eating more vegetables than fruit to avoid spiking your blood sugar, as this can also impact mood, concentration, and fatigue, and when blood sugar falls it can zap your energy and ability to focus.

Eat foods that feed good bacteria

A high fiber plant-based diet helps feed the good bacteria in the gut, which is another reason for eating more fruit and vegetables. Additionally, fermented foods can improve the diversity of the bacteria in your gut and create a healthier microbiome, so eat more of the following:

  • natural (plant-based) yogurt
  • sauerkraut
  • kimchi
  • natto
  • tempeh
  • kombucha
  • kefir

Get your healthy fats for brain health

Little known fact: The human brain is nearly 60 percent fat, and it needs essential fatty acids from foods to function correctly. Research indicates that omega-3’s have positive effects on mental health, and people eating a mostly plant-based diet need to get these beneficial omega-3 fatty acids from sources other than fish, such as algae, flaxseeds, hemp, and walnuts. Taking spirulina and chlorella can help provide the omega-3s your brain needs.

Additionally, for brain health, add healthy polyunsaturated fats such as nuts, seeds, olive oil, and avocado.

Foods that reduce stress and lower cortisol

It's essential to keep cortisol, the body’s stress hormone, in check, since chronically raised cortisol levels due to stress can dampen the immune response and impact physical and mental health. The American Institute of Stress (AIS) advises that dark chocolate, bananas, and garlic can all help lower cortisol levels. The AIS also recommends avoiding caffeine, processed foods, and sugary drinks, such as soda, which can all impact stress and mood.

Drink tea, particularly green

The AIS recommends drinking tea to reduce stress. This is because tea contains an amino acid, l-theanine, that can help you to relax. Matcha green tea is a particularly rich source of l-theanine, but other teas also contain it. In addition, herbal teas such as lemon balm, chamomile, and lavender may be effective for stress, although research is limited.

Bottom Line: For mental health, eat 6 to 8 servings of fruit and vegetables a day

A healthy plant-based diet that includes a variety of fruit and vegetables along with essential fatty acids such as omega-3 can help avoid the adverse effects of stress. Additionally, including fermented foods and green tea and avoiding caffeine and added sugar can support your gut and help to balance your cortisol levels.

For more great content like this, check out The Beet's Health & Nutrition articles.