An Introduction to Nutritional Psychology

What science has on diet’s relationship with mental health

These days, it seems like every diet is always somehow inextricably linked to mental health — whether it be some foods groups claimed to trigger a slew of hormonal release, causing imbalance, or instead hold stance of the opposing argument, such as fish oil’s antidepressant effect. Research and studies have followed suit, with a scrambling barrage of evidence all over the internet about diet and its impact to the human mood.

The link between diet and mood may seem far-fetched and mere headline-grabbing stunts, but the theory behind nutritional psychology is actually pretty sensible and straightforward. Dietary changes, such as cutting back on junk foods — highly processed meats, sugars, unhealthy oils — can change the way our brains function on a cellular level. This in return triggers a positive impact on mental health.

Dr. Eva Selhub, a Clinical Associate of the world-renowned Benson Henry Institute for Mind-Body Medicine at the Massachusetts General Hospital, says that the fuel that keeps our brain running comes from food, and so what you eat directly affects the structure and function of your brain and, ultimately, your mood.

Your diet is a lot like fuel for your car, and like an expensive car, your brain is able to function at peak levels when it gets only premium fuel. Makes sense, right? “Eating high-quality foods that contain lots of vitamins, minerals, and antioxidants nourishes the brain and protects it from oxidative stress, which can damage cells”, says Dr. Selhub.

And just like an expensive car, damage is inevitable if you consume anything other than premium fuel. If contaminants from impure oil (such as what you get from processed or refined foods) get to the brain, it has little ability to get rid of them. When translated to day-to-day functioning, impairment will ensue.

Dr. Eva Selhub claims that “diets high in refined sugars, for example, are harmful to the brain.” We’ve all heard of the horrifying effects that sugar poses to weight gain, but Dr. Selhub adds that “[sugars] also promote inflammation and oxidative stress. Multiple studies have found a correlation between a diet high in refined sugars and impaired brain function”. And guess what, studies have found that sugars can even worsen symptoms of mood disorders, such as depression.

How does that happen? Well our gastrointestinal tract, or what we often refer to as the gut, plays a major role in here. As the unit responsible for the entire digestion process, our gut is lined with millions of epithelial cells, which helps absorb nutrients, specialised cells, which helps produce digestive enzymes, and nerve cells. In fact, there are over one hundred million nerve cells in the gut.

The nerve cells act as a supervisor who overlooks the entire digestion process, to ensure they work in unison, as needed, when needed. But that’s not the only role it plays. It also produces 90% of our body’s serotonin, which is a neurotransmitter that helps regulate sleep and appetite, mediate moods, and inhibit pain. So as a collective system of organs and cells, our gastrointestinal tract do not just help digest food, but also guide our emotions.

The food we eat greatly affects the types of bacteria that reside in our guts, and that matters since that’s where our serotonin power-plant is located. Two papers published in 2019 showed that when microbiota-containing fecal matter humans with schizophrenia or depression is transplanted into rodents, the animals exhibit behaviours that are similarly seen in humans.

Dr. Drew Ramsey, a psychiatrist and professor at Columbia University, says that “if you’re missing certain nutrients, such as vitamin B12, iron and omega-3 fatty acids, you may get depressed.” Additionally, studies have also shed light on the unseemly health effects of the western diet, showing that it is associated with changes in the size of the hippocampus, a tiny organ in the brain that’s responsible for memory and learning.

The evidence don’t end there. There is a growing body of research revealing previously unknown correlations between diet and mental health. This 2015 paper highlights that certain foods increase systemic inflammation, which may be a key aspect for the development of chronic diseases, including depression.

The gut microbiome is again called into action here, as they protect the intestinal lining by forming a barrier to ensure the body is well protected against toxins and potentially lethal pathogens. The collective impacts of a healthy microbiome sees your nutrient absorption improve, suppresses inflammation, and activate neural pathways via serotonin to control mood and appetite.

The latest research on probiotic consumption — composed of live microorganisms which boosts your gut microbiome — also show improvements in symptoms for depression and anxiety.

Though these findings are promising, let’s not forget that the field of nutritional psychology is still quite young. Most studies are currently based on animal models and employ short-term observations, which may shield us from vital clues and information as to the long-term efficacy and safety of diets formulated based on these findings.

This promising field has already birthed new institutions and courses, which offer certifications in nutritional psychology in as short as 9-month courses — most of which even lack requirements for prior certification in science. This is an obvious red flag, signifying the lack of important safeguards, such as standardised treatment protocols or formal training requirements — or regulations of any kind.

“That’s reason enough, experts say, to take a good, skeptical look at anyone who calls themselves a nutritional psychologist before signing up for their take on yesterday’s breakfast”, writes science journalist Brittany Risher. The theories seem sound, the framework is there, and the people seem ready, but we just have to be a little bit more patient.

One piece of actionable advice we can take away from this is to start becoming more thoughtful with the foods we eat. Pay attention to how eating different foods makes you feel — not just as you’re eating — but the next day. Dr. Selhub suggests “eating a ‘clean’ diet for two to three weeks, cutting out all processed foods and sugar, and then seeing how you feel.”

After evaluating your feelings and overall wellness, slowly re-introduce foods back into your diet, one by one, while taking notes about how you feel, noticing even the slightest changes in mood or other feelings.

“When some people “go clean”, they cannot believe how much better they feel both physically and emotionally, and how much worse they then feel when they reintroduce the foods that are known to enhance inflammation.”

Considering the current circumstances, now seems like a good time to experiment with different food groups. Perk up your mental ears, sink your thoughts into your feelings, and observe how your feeling and mood changes with different meals. And don’t forget to social distance, exercise, wash hands, and rest well while you’re at it.

Junior doctor, writer, photographer, and part-time social media strategist. Receive weekly updates from me ⤵

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