Energy production in the brain constantly “burns” oxygen and sugar (glucose). The brain’s energy system relies on a delicate balance of nutrients and metabolic processes to function optimally. Oxygen and sugar (glucose) are the most important nutrients, as the brain requires them constantly. Any interruption of the supply of oxygen or sugar leads to serious consequences, but both can be very harmful to the brain.
Oxygen is essential for sustaining cellular respiration (the breathing of cells) and energy production. It is primarily delivered to the brain through the bloodstream. Insufficient oxygen supply can lead to neuronal cell death or impaired cognitive function.
However, along with its benefits, oxygen can also pose a threat by generating reactive oxygen species (ROS) (1). ROS can cause oxidative damage to brain cells (neurons and glial cells), contributing to neurodegenerative disorders such as Alzheimer’s and Parkinson’s diseases (2, 3). Various antioxidant defense mechanisms mitigate the brain’s vulnerability to oxidative stress.
Glucose, a simple sugar obtained from the diet, is a primary fuel source for the brain.
Regarding energy metabolism, our brain predominantly relies on glucose transported into brain cells (neurons and glia), where energy is produced in the form of ATP (glycolysis). A secondary energy source is galactose, another sugar derived from lactose in dairy products; however, this process is less efficient than utilizing glucose. Lastly, ketones, the products from the breakdown of fats, can be considered an alternative energy source (e.g., during prolonged fasting). This doesn’t mean that you have to consume sugars, as the body can keep a sufficient amount of glucose (from protein and carbohydrates in the diet...) even during fasting.
On the contrary, access to sugar is an issue in the modern world. In the past, access to sugar might have been limited, but in today’s world, it’s widely available. The issue lies in overconsumption and its adverse impacts on health, particularly concerning memory function (negative effect on long-term potentiation and memory creation). In higher amounts, sugar is toxic and can cause inflammation and thickening of the walls of your blood vessels. This can obstruct blood delivery (and thus oxygen) to all parts of the brain. You could say that sugar is the most accessible ‘brain killer.’
The cornerstones of a properly functioning energy system of the brain are energy production (mitochondria), additional energy storage (astrocytes), and, first and foremost, the delivery system (bloodstream).
The number one piece of advice to maintain all energy subsystems (healthy bloodstream, productive mitochondria in sufficient numbers, and operational astrocytes) one can follow is regular exercise and a consistent supply of elementary micronutrients. Vitamin C, Rutin, and various polyphenols are among the most important ones and can all be obtained from a healthy diet (e.g., berries, veggies, and fruits – but please not too much fruit).
Oxygen and sugar are the most essential nutrients of the brain’s energy system, with one key difference. With oxygen, it takes an effort to have enough of it in all brain parts permanently. With sugar, it takes a significant effort to avoid an excess amount. In other words, when it comes to the energy system of the brain, the most probable harm for the brain comes from a lack of oxygen and a toxic amount of sugar.
References
Singh A, Kukreti R, Saso L, Kukreti S. Oxidative Stress: A Key Modulator in Neurodegenerative Diseases. Molecules. 2019 Apr 22;24(8):1583. doi: 10.3390/molecules24081583. PMID: 31013638; PMCID: PMC6514564.
Tönnies E, Trushina E. Oxidative Stress, Synaptic Dysfunction, and Alzheimer's Disease. J Alzheimers Dis. 2017;57(4):1105-1121. doi: 10.3233/JAD-161088. PMID: 28059794; PMCID: PMC5409043.
Dias V, Junn E, Mouradian MM. The role of oxidative stress in Parkinson's disease. J Parkinsons Dis. 2013;3(4):461-91. doi: 10.3233/JPD-130230. PMID: 24252804; PMCID: PMC4135313.
Baxter PS, Hardingham GE. Adaptive regulation of the brain's antioxidant defences by neurons and astrocytes. Free Radic Biol Med. 2016 Nov;100:147-152. doi: 10.1016/j.freeradbiomed.2016.06.027. Epub 2016 Jun 27. PMID: 27365123; PMCID: PMC5145800.
