Nutritional Psychology – How Diet Affects Our Brain

Do you ask for a super-sized helping of fries with your fast-food burger? Or do you prefer a chicken salad with light dressing on the side? Whichever dietary choice resembles your own, nutrition has a vast impact on how we think, feel, and behave.


Nutritional psychology explains how nutrition determines cognitive skills, mood disorders, and intelligence.


Nutritional psychology is the study of nutrition and how it relates to mood, behavior, and mental health. The foods we eat influence psychological, behavioral, cognitive, perceptual, sensory, and psychosocial patterns. This area of study has the goal to implement education to the masses about nutrition and its connection with mental health.


Most people think of the nervous system running up the spine to the brain.

However, did you know that a large portion of the nervous system is in our gastrointestinal tracts? From chewing food to absorption and even elimination, the gut is home to millions of nerve cells, hormones, and enzymes – each performing a whole slew of functions. This is why it is commonly referred to as our “second brain.”

Together, the gastrointestinal tract and its connections are called the enteric nervous system.


Gut bacteria line the stomach and intestines to help with digestion.

These bacteria make neurotransmitters that not only control digestion, but also control key cognitive processes like memory, mood, and learning.

In fact, Serotonin is a particularly prominent neurotransmitter in the gut. Bacteria create nearly 95 percent of the body’s serotonin. This helps to stabilize mood and trigger peristalsis (contractions of the stomach and intestines to digest food). When serotonin levels are off, it can cause symptoms of nausea, vomiting, and constipation.

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However, serotonin is not the only neurotransmitter. GABA and dopamine are also very important. Studies have allowed experts to document things like mood changes in the presence of “functional gastrointestinal disorders” (tummy problems) such as irritable bowel syndrome.

It was once also thought that emotions and disorders like anxiety and depression result in bowel symptoms. However, scholars at John Hopkins now believe that an unhealthy gastrointestinal tract leads to anxiety and depression. In other words, we now think it’s the opposite – guts affect the brain.


The food we consume literally has the power to alter brain structure.

A 2018 study published in the Journal of Neuroscience reveals interesting results in brain imaging and grey matter when it comes to food. Patients who made food choices based on whether a food item is healthy rather than on taste or indulgence showed an increased volume of grey matter in the prefrontal cortex. Judging grey matter “volume” in these areas can be helpful in predicting various eating disorders including obesity and anorexia nervosa.

Food also affects neurons (nerve cells in the brain).

Diets with a high fat and sugar content have fewer synapses in the brain’s hippocampus. These are the connections that transmit signals to other cells in the body. Fewer neurons mean the brain is less efficient at neuroplasticity. It cannot adapt as quickly. Instead, the hippocampus becomes inflamed as the cells respond to harm.


The term obesity means someone has a body mass index (BMI) of 30 or greater. And, there are more than 400 million obese adults worldwide.

Being overweight has a vast impact on the body. Although someone who is obese is prone to developing heart disease, diabetes, and hypertension, the brain is particularly affected. Scientists have attributed multiple cases of cognitive impairment to obesity.   

The brain of obese individuals is vulnerable to cerebral atrophy. The brain literally shrinks. As the brain volume decreases in size, the likelihood of memory impairment increases with age. A lack of brain volume makes it difficult to resist over or binge eating – which fuels the vicious cycle.


The first line of defense against the obesity epidemic is to take on a healthy diet and lifestyle.

Diet and exercise are key to shedding the extra pounds because it burns more calories than one expends. However, restricting caloric intake is potentially detrimental to psychological health.

Studies show that caloric restriction is linked to depression – a mental health disorder where someone experiences unexplained sadness, anxiety, loss of interest, low motivation, and interrupted sleeping and eating patterns for more than 2-weeks.

Some male subjects went from consuming 3,200 calories to 1,600 calories of foods such as potatoes, turnips macaroni, milk, bread, chicken, and rutabagas. As a result, these men reported a multitude of symptoms, including…

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  • Dizziness
  • Cold intolerance
  • Fatigue,
  • Muscle aches
  • Edema
  • Reduced sex drive
  • Low attention spans
  • Poor concentration
  • Psychological distress

Some even went to a psychiatric hospital for self-mutualization and suicide attempts.

But on the other hand, other studies show that the risk for dementia and cognitive decline is lessened by a lower caloric intake. The combination of studies shows us that the quality of food choices is important. For our brains to thrive, we require a range of foods from all food groups to avoid nutritional deficiencies or physiological dips.


Carbohydrates are the body’s main source of fuel.

When we consume carbohydrates, the body breaks them down into glucose. The nerve cells use the glucose in the bloodstream for energy. Restricting carbohydrates, like so many modern day dieters do, is depriving the body of its main source of fuel. Thus, cognitive skills are affected.

Researchers at Tufts University tested this hypothesis. The study divided women into two groups based on “low-carb” and “low calorie” diets. They also had cognitive skills tests before , during, and after the study. Those on low carbohydrate diets presented with poor memory performance within a week of their diet.

In the average Western diet, the type of carbohydrates has an impact too.

Refined, processed carbohydrates result in repeated spikes in blood glucose levels. This triggers the rapid release of stress hormones that increase anxiety and mood disorders.


Fast comprises 70 percent of the human brain. So, fats are critical for brain development. When the body does not have sufficient carbohydrates available, it uses fat to perform necessary functions. Psychiatrists at Harvard University discovered that the amount of fat an individual consumes has little impact on brain function; however, the form of fat does.

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Omega-3 fatty acids are beneficial dietary fats. We find them everywhere – like in fish, walnuts, and chai seeds. Other fats, like saturated fats, are good in moderation and come from meat, coconut, and dairy products. It’s best to avoid hydrogenated fats (i.e. trans fats) that are processed or deep-fried.


Vitamins and minerals are also related to brain function.

The body is exposed to free radicals. Free radicals are unstable cells that damage healthy cells. The result is disease, aging, and illness. Vitamins and minerals contain radical-fighting substances known as antioxidants.

The following vitamins and minerals are essential:

  • Iron — Adults and children who are anemic score lower on cognitive tests.
  • B Vitamins — B vitamins for the brain include B12, B6, and B9 (folate). When B vitamins are lacking, the body cannot convert homocysteine into protein. As homocysteine builds up, cognitive performance suffers.  
  • Vitamin C — Vitamin C aids in iron absorption, but it does affect the brain directly. It is responsible for building the myelin sheath that allows the nerves to communicate. Vitamin C helps with manufacturing neurotransmitters like dopamine and serotonin.
  • Vitamin D — Sunlight and some foods give us Vitamin D. Similar to vitamin C, vitamin D works with nerve growth. Experts claim vitamin D activates certain enzymes to produce neurotransmitters and reduce inflammation.
  • Vitamin E — Vitamin E is the main vitamin that combats neurodegeneration in the brain by reducing oxidative stress. When compounded with other vitamins, it improves memory and cognitive thinking processes.
  • Zinc — Deficiencies in zinc reflect issues with language and numbers. Patients with Alzheimer’s disease tend to have a zinc deficiency, which provides evidence that zinc aids in cognitive function.
  • Magnesium — Unrefined grains (i.e. buckwheat), green leafy vegetables, and nuts (i.e. almonds, cashews) are sources of magnesium. This deficiency is common in third-world countries and vegetarians.


Dementia is an umbrella term for neurodegenerative illnesses that cause impaired cognitive skills.

Those with dementia experience memory loss, confusion, difficulties with language, and problem-solving abilities that all interfere with normal daily functioning. The most common form of dementia is Alzheimer’s disease.

Published in April 2020’s edition of the American Academy of Neurology, people who mostly eat snack foods (i.e. cookies, cakes), processed meats, and starchy foods such as potatoes, have a higher risk of dementia than people who eat from a diverse range of food groups.

Also, previous studies confirm that greater caloric intake is associated with Alzheimer’s.  

Alzheimer’s Association has actually put out a dietary guideline for the world to use. It’s also a treatment for the condition. Patients have an increase in memory and an overall reduction in the progression of the disease. There are two recommended diets…

  • DASH Diet—DASH stands for The Dietary Approaches to Stop Hypertension. It promotes a diet to lower blood pressure, which reduces stress on the nervous system. Someone following the DASH diet should reduce their intake of excessive amounts of sodium, fats, red meats, full-fat dairy products, sweets, sugary beverages and to consume lean meats (i.e. poultry, fish), whole grains, nuts, fruits, and vegetables.

  • The Mediterranean Diet—The Mediterranean diet limits red meat, replaces butter with healthy alternatives and focuses on a diet of fruits, fresh vegetables, nuts, and whole grains. People in this diet should eat fish and poultry twice a week adn replace salt with speices.


Much like a diet of fruits, green leafy vegetables, whole grains, lean meats, nuts, and seeds are healthy for the brain, there are many foods that have the opposite effect. The chemicals in the foods we eat are stored throughout the body, including the brain and nervous system.

Soft Drinks

Sugary soft drinks include high fructose corn syrup. High fructose corn syrup is 55 percent fructose and 45 percent glucose. The inflammatory substance incorporated into our favorite beverages is known to impair memory. For example, high fructose corn syrup affects brain function because of it leads to insulin resistance. When the body is unable to bring blood glucose levels to normal ranges, the increase levels are damaging to the brain.

Refined Carbohydrates

Refined carbohydrates are processed grains like white flour. They have a high glycemic index in which the body reacts with a spike in blood sugar levels. Studies of the elderly proved that the risk of dementia and mild cognitive impairment is nearly doubled in the population who received over half of their dietary caloric intake from unhealthy carbohydrates. Whole, unrefined grains, fruits, and vegetables are healthier alternatives.

Trans Fats

Naturally occurring trans fats in meat and dairy products are not dangerous in controlled amounts. However, hydrogenated vegetable oil, margarine, pre-packaged desserts, frosting, and shortening are foods hiding the brain’s silent killer. Synthetic trans fats are harmful to cognitive function, as well as cardiac health. It advances inflammation.

Artificial Sweeteners

“Sugar free” is not always the healthier option. Aspartame and artificial sweeteners are in sugar free products. Aspartame is made from the amino acids aspartic acid and phenylalanine. If aspartame is consumed, the body breaks it down into methanol which is toxic in large amounts.

Studies show artificial sweeteners provoke behavioral changes, depression, and learning difficulties. Participants consumed 11 mg of aspartame for every pound of body weight. After eight days, they scored lower on cognitive tests, were irritable, and had increased rates of depression in comparison to control subjects.


Alcohol impairs the way in which the brain communicates and decreases brain volume. Those who frequently consume alcohol typically develop a B vitamin deficiency, which is connected to poor cognitive transparent pharmacy functioning. Most detrimental effects stem from episodes of binge drinking. But it’s young people should avoid alcohol because it interferes with brain development. Teenagers who drink are susceptible to risky behaviors and alcohol dependence into adulthood.


So, what diet is best for your brain?

Low carb, high carb, high fat, low fat, calorie restriction? “Best” easing habits don’t come in any single diet. It is learning to be intuitive with your body’s nutritional needs, consuming a diet as colorful as the rainbow, and incorporating a variety of foods from all food groups. It is about establishing a balance that allows your body and brain to thrive.


American Academy of Neurology. (2020, April 22). Which foods do you eat together? How you combine them may raise dementia risk: Study finds ‘food networks’ centered on processed meats, starches may raise risk. ScienceDaily. Retrieved November 22, 2020 from

Harvard University. Protect your brain with “good fat.” Retrieved from

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