*Disclaimer: I am not a registered dietitian, naturopath, doctor, or other type of healthcare professional. This is simply the product of my own research and opinions, not to be used to replace the recommendations of a registered healthcare professional.
The brain is the most powerful and complex organ in the body and is responsible for our every thought, movement, emotion, speech, memory and perception. One of the ways in which we can optimize these cognitive processes are through food!
Most of our brain matter consists of the three main macronutrients: fatty acids (fats), amino acids (proteins) and monosaccharides (carbohydrates); as well as micronutrients (vitamins and minerals). In order to understand why we need an adequate amount of these micro and macronutrients in our diet, we must first discuss the role of these three main classes of nutrients in our cognitive functioning and brain composition.
Summary of the 3 Main Macronutrients
Starting with carbohydrates, this is the group that includes sugars and their main function is to provide the brain with its primary source of energy; glucose (a type of sugar). If the brain doesn’t receive adequate glucose, the communication between neurons and chemical messengers become severed over time, resulting in negative effects associated with information processing, neurotransmitter formation and energy levels.
Next up is fats. The main functions of dietary fats include: 1) to serve as structural components of cell membranes, 2) helps absorb vitamins and minerals, 3) acts as hormone precursors; and 4) long-term energy storage. Eating dietary fats provides you with the essential fatty acids and fat-soluble vitamins you need to keep your body functioning properly. These fatty acids can be grouped into two main types: saturated fats and unsaturated fats (monounsaturated and polyunsaturated fatty acids). More than 60% of your brain is composed of fats, specifically omega-3 and omega-6 fatty acids (two types of unsaturated fats). Your brain needs these unsaturated fats to support cognitive processes - which is a fancy way of saying that you need fats in order to improve your thinking, memory, judgement, and problem-solving abilities.
Lastly, amino acids are the building blocks of proteins and play a primary role in controlling the body’s cellular processes. All proteins are composed from the same pool of 20 amino acids, including the 9 essential ones that cannot be synthesized by the body; and must be ingested through food. Although the majority of our brain matter is made up of fats, proteins play a vital role in the synthesis of various neurotransmitters and neuromodulators, including dopamine and serotonin:
- Involved in feelings of reward, motivation, memory, attention; and regulating body movements.
- Low levels of dopamine have been linked to reduced motivation and enthusiasm for things that would commonly excite a person.
- Dopamine synthesis requires the amino acid Tyrosine, which directly converts to L-DOPA (the precursor to Dopamine).
- This is involved in the regulation of mood, social behaviour, appetite, emotions; as well as motor, cognitive and autonomic functions.
- Serotonin is commonly referred to as the "happy chemical". Studies have found a strong link between depression, anxiety, OCD and low levels of serotonin. However, it is unclear whether low serotonin levels are what causes depression, or whether depression causes the fall in serotonin levels.
- Serotonin synthesis requires the precursor amino acid, Tryptophan, which is found in protein-rich foods such as chicken, egg, turkey, tofu and soy.
Maximize Your Brain's Potential
Now that I have covered a brief summary of the functions behind these three types of macronutrients, I will discuss some of the scientific literature, in order to emphasize why it is critical to be mindful of your food choices in order to improve your brain health. It is well researched that nutrition has significant effects on cognitive functioning, specifically for regulating emotion, memory, learning and sleep. For the purpose of this post, I will be referring to studies investigating the effects of the Mediterranean diet on brain function, as it involves the consumption of all food groups, without any exclusions, unlike the ketogenic, vegan/vegetarian, and paleo diets. The Mediterranean diet is abundant in fruits, vegetables, whole grains, legumes and healthy fats. It also favors lean sources of protein like fish and poultry, rather than red meats (which are higher in saturated fats).
To begin, let’s discuss blood sugar. Remember, glucose is the brain’s primary source of energy, so it’s important to eat an adequate amount of carbohydrates. However, it is important to note that not all carbohydrate sources affect blood sugar the same way. It is necessary to avoid eating excess simple carbohydrates (like refined sugars) that instantly spike your blood sugar; and instead, opt for complex carbohydrate choices (like high-fiber foods) that provide your brain with a steady influx of glucose rather than a sharp spike and rapid fall. To put it simply, when your blood sugar spikes, the glucose is getting into your blood stream quickly, but will also drop at that same rate - which leaves you feeling lethargic, irritable and hungry. The ranking of how different carbohydrate sources affect blood sugar levels is known as the glycemic index. Carbohydrates with a low glycemic index release glucose slowly, giving the brain a steady supply of energy; compared to high glycemic foods, which release glucose rapidly. Over time, the overconsumption of high glycemic foods can negatively alter brain function and promote overeating. Examples of low glycemic foods include: some fruits (like berries), raw carrots, kidney beans, chickpeas, and lentils; and examples of high glycemic foods include: bread, rice, potatoes, processed food, cereals and dates.
Interestingly, a 2017 study found that individuals with a high level of sugar consumption were 23% more likely to be diagnosed with depression compared to those with a lower sugar intake . The study found 4 potential mechanisms as to why sugar intake can be associated with risk of depression:
1) High sugar intake decreases levels of a protein called BDNF (involved with survival, growth and maturation of neurons), which was found to cause neuron death and hippocampus atrophy (shrinkage of the hippocampus). The hippocampus is a part of the brain that is associated with memory and learning.
2) High carbohydrate and high saturated fat consumption were found to increase inflammation in the body, which is believed to play a role in causing insulin resistance (resulting in high levels of blood glucose) and metabolic disturbances . Inflammation plays a central role in healing, but chronic inflammation causes the body to be in a prolonged state of emergency; which has a detrimental effect on the communication signals in the brain and can lead to increased risk of arthritis, heart disease, and Alzheimer's disease.
3) High sugar diets can lead to hypoglycemia (low blood sugar), which sounds contradicting but would make sense due to the rapid blood sugar spike and the rapid decline that follows. This is said to influence hormone levels, ultimately negatively affecting mood .
4) The addictive impact of refined sugars can have a huge influence on dopamine receptors. The way your brain reacts to sugar is very similar to the way it would react to substances such as cocaine, where the brain produces a huge influx of dopamine. It’s important to keep in mind that too much and too little dopamine can have detrimental effects on mental health. Studies show that a deficiency in dopamine is linked to the development of Parkinson’s Disease, whereas an excess of dopamine is associated with mania, hallucinations and Schizophrenia.
In another 2017 study, the relationship between the Mediterranean diet and components of cognitive function domains (memory, language, attention speed, executive functioning, visuo-spatial perception) were studied . This study found that memory, language and decision-making functions were positively associated with diet, with the exception of attention and speed of information processing. Additionally, lower dietary intakes of fruits, vegetables and fish were seen in individuals with dementia, compared to those without the disease . The study found an association with dementia diagnosis and fish consumption, where dementia risk was decreased by almost 70% with daily fish consumption and by 10% with weekly fish consumption. The proposed mechanism for this relationship is that fish contains high amounts of monounsaturated and polyunsaturated fats, which are linked to learning and memory function. Specifically, the most abundant fats in the brains are omega 3 and omega 6 fatty acids, where a diet with adequate amounts of these fatty acids have been linked to a decrease in degenerative brain conditions. Dietary consumption of omega-3 fatty acids is one of the best-studied interactions between food and brain evolution. Some examples of foods that are high in omega fatty acids include: salmon, cod, flax seeds, chia seeds, walnuts, and soybeans.
On the other hand, in a 2010 study, it was found that consumption of saturated fats has been linked to cognitive decline in adult rodents, worsening of cognitive impairment after brain trauma in rodents; and a cognitive decline in aging humans. Sources of saturated fats include butter, coconut oil, dairy products and meat .
Further, as you age, you naturally lose brain cells and, thus, your brain starts to shrink. This is an extremely slow, natural process. Alternatively, brain atrophy occurs more quickly and is much more damaging. Brain atrophy involves the rapid loss of neurons, eventually leading to brain shrinkage; and usually results from brain-degenerative diseases such as stroke or Alzheimer’s disease .
In a 2017 study, the association between the Mediterranean diet and the effects of aging on brain structure was investigated . Results from this study indicated that the greater the adherence to a Mediterranean diet, the greater the protective effect against brain atrophy. This conclusion has also been supported by three other studies. The author of this study noted that it is extremely difficult to be able to narrow down the specific food and nutrients that have direct effects on brain atrophy; and that the contribution of the combined food components and their interactions is what increases the benefits to brain health. With all this being said, these studies are still limited by confounding variables, such as education and socioeconomic status; and require further research in order to establish a causal relationship. Lastly, it’s important to note that these studies also state that the combination of both food choices and exercise produces the best results, rather than the effects of food choice or exercise on their own.
In conclusion, our brain is highly sensitive to the foods we eat. It is crucial to have a balanced and nutritious diet that includes all of the essential micro and macronutrients for optimal brain function. To put things simply, you want a diet that includes sufficient carbohydrates, unsaturated fats and proteins; while limiting saturated/trans fats. If your nutrient intake does not meet your brain's metabolic needs, you will be more susceptible to experiencing cognitive decay compared to those who are consuming sufficient nutrients. Remember that the brain is the most metabolically active organ in the body, so ensuring that you’re meeting its nutritional requirements is crucial for optimal cognitive functioning.
Do you notice a difference in your mental health when you make healthy choices? Let us know in the comments below!
 Anastasiou CA, Yannakoulia M, Kosmidis MH, et al. Mediterranean diet and cognitive health: initial results from the Hellenic Longitudinal Investigation of Aging and Diet. PLoS One. 2017;12(8):e0182048.
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 Knüppel A, Shipley MJ, Llewellyn CH, Brunner EJ. Sugar intake from sweet food and beverages, common mental disorder and depression: prospective findings from the Whitehall II study. Sci Rep. 2017;7(1):6287. doi:10.1038/s41598-017-05649-7
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 Medical University of Vienna. (2016, August 31). Dopamine: Far more than just the 'happy hormone'. ScienceDaily. Retrieved July 10, 2020 from www.sciencedaily.com/releases/2016/08/160831085320.htm