Carbohydrates: Food for Thought

The first things that come to mind when thinking about carbohydrates is probably that unli rice in Mang Inasal, or that blueberry cheesecake displayed in the bakery. Simply put, carbohydrates are the sugars, starches or fibers found in most of the food that we eat, such as grains, fruits and vegetables.

Sources of carbohydrates (Source: Oleksandra Naumenko)

The first things that come to mind when thinking about carbohydrates is probably that unli rice in Mang Inasal, or that blueberry cheesecake displayed in the bakery. Simply put, carbohydrates are the sugars, starches or fibers found in most of the food that we eat, such as grains, fruits and vegetables.

With the current hype about its detrimental effects, it is not uncommon that most of us become overly concerned with avoiding carbohydrates. Healthy food fads and diet advertisements have gained popularity over the years, and this mindset has created a battle between cravings versus avoidance. For some people, fitting in with the current trends results in extreme restriction or binging, a perfect environment for eating disorders to emerge. Despite the negative connotation surrounding carbohydrates, the fact remains that this macronutrient is needed for the brain and body to function properly. But how exactly is it digested?

Digestion of carbohydrates (Source: Netter’s Atlas of Human Physiology, 1st Edition)

When we consume food, such as a pizza slice, mechanical digestion breaks it down into smaller pieces and mixes with saliva, where salivary amylase breaks down long glucose chains into smaller chains. As it reaches the stomach, the acidic environment stops the function of the salivary amylase. Most of the digestion happens in the small intestine due to the action of pancreatic amylase. This enzyme breaks down starch into small oligosaccharides containing three to ten glucose molecules, and maltose which contains two glucose molecules. The final steps of digestion is done by the enzymes produced by enterocytes, cells found on the surface of the small intestine. Maltose is digested by maltase, forming two glucose molecules, while lactose, from cheese, is broken down into glucose and galactose by lactase. Sucrose in the sauce is digested by sucrase to form glucose and fructose. These are now absorbed into the bloodstream, into the liver, where fructose and galactose are converted into glucose, which can be used by the body.

The brain requires around 130 grams of carbohydrates per day. This amount of glucose is necessary for the brain and nervous system to optimally function. It is fascinating that the brain only accounts for 2% of our total body weight, but consumes around one-fifth of our total energy needs. One can say that carbohydrates are the body’s main source of fuel, with our neurons requiring the highest amounts of glucose.

Aside from its role as a source of energy, carbohydrates also perform certain functions in the brain. One of these is acting as a modulator to the creation of neurotransmitters, which are the chemical messengers of the body. In particular, serotonin and dopamine, more commonly known as ‘happy hormones’, are affected by our carbohydrate intake.

The precursor of serotonin, tryptophan, is an amino acid found in cheese, eggs and meat. Often, tryptophan cannot easily enter the brain due to the effect of other amino acids. However, when we eat a meal high in carbohydrates, the body releases insulin, allowing the entry of tryptophan. As more enters the brain, more of the neurotransmitter is produced, which can have a direct effect on our mood and well-being. Similarly, dopamine requires carbohydrates to be synthesized. This neurotransmitter is produced by dopaminergic neurons from tyrosine, when we eat food that we crave or when we do things that bring pleasure and satisfaction.

Carbohydrates also aid in regulating proper blood flow and assist the brain in processing information. Studies have found that people who consume insufficient amounts of carbohydrates exhibited decreased memory and reaction time. On the other hand, eating a large amount of carbohydrates has been linked to an increased risk in developing learning disorders, as well as depression and poor memory. In addition, excessive amounts diminishes the ability of the brain to tell you when you are truly full due to the diminished activity of the brain’s oxytocin system which is responsible for our satiation. This may be linked to the decrease in the brain chemical known as the Brain Derived Neurotrophic Factor (BDNF). Excess refined sugar in the body decreases the amount of BDNF in the brain, resulting in decreased memory and learning capabilities. Furthermore, low BDNF levels also lowers the ability of the body to protect itself from insulin resistance, leading to Type II diabetes.

Despite the many misconceptions regarding carbohydrates, it is important to remember that moderation in everything is the key to maintaining our physical and mental health. The avoidance or overconsumption can change the way the brain functions in many areas. During these times of uncertainty, it is up to us to be informed and be aware of changes and adjustments in our lifestyle. Always remember: Do-nut forget to take care of your health!

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References:

Conrad, B. The role of dopamine as a neurotransmitter in the human brain. Essential research tools for neurodegeneration & neural signaling. https://www.enzolifesciences.com/science-center/technotes/2018/november/the-role-of-dopamine-as-a-neurotransmitter-in-the-human-brain/

D’Anci, K. E., Watts, K. L., Kanarek, R. B., & Taylor, H.A. (2008). Low-carbohydrate weight-loss diets. Effects on cognition and mood. Appetite, 52(1), 96-103. 10.1016/j.appet.2008.08.009

Gal, N. J., Ford, A. L., & Dahl, W. J. (2018). Facts about Carbohydrate. IFAS Extension University of Florida. https://edis.ifas.ufl.edu/pdffiles/FS/FS24300.pdf

Jenkins, T. A., Nguyen, J. C. D., Polglaze, K. E., & Bertrand, P. P. (2016). Influence of tryptophan and serotonin on mood and cognition with a possible role of the gut-brain axis. Nutrients, 8(1). 10.3390/nu8010056

Koeppen, B. M., & Hansen, J. T. (2002). Netter's Atlas of Human Physiology. Elsevier Inc.

Molnar, C. & Gair, J. (2015). Chapter 15.3 Digestive System Processes. Concepts of Biology- 1st Canadian Edition, OpenStax College.

Molteni, R., Barnard, R. J., Ying, Z., Roberts, C. K., & Gómez-Pinilla, F. (2002). A high-fat, refined sugar diet reduces hippocampal brain-derived neurotrophic factor, neuronal plasticity, and learning. Neuroscience, 112(4), 803-814. https://doi.org/10.1016/S0306-4522(02)00123-9