The Pillars of Brain Health: Nutrition

But all this ability comes at a price: Our brains are metabolically expensive – meaning they account for roughly 20% of daily energy expenditure, compared to about 8% in modern primates. When looking at our evolutionary past, it’s clear that as the quality and diversity of our ancestors' diets improved, their brains were able to increase in size. This increase in brain size corresponded to a smaller gastrointestinal system, since their diets meant they needed to do less digestive “work” to obtain nutrients. The extra energy that was available from a shrinking gut could be channeled to the brain, helping promote its growth and development. A high-quality, nutrient dense diet – in conjunction with other aspects of daily living, such as exercise – has had a crucial role in shaping cognitive capacity and brain evolution.

Our brains continue to require a steady stream of high-quality, nutrient-dense food to function. In order to feed our hungry brains, we have to provide them with plenty of metabolic energy. In most cases, glucose represents the primary metabolic fuel used in the brain to produce cellular energy (ATP). Once glucose makes its way into the brain, various vitamins and minerals facilitate glucose oxidation in the mitochondria, with certain B vitamins and lipoic acid playing key roles in the reaction. In order to fully oxidize glucose, the brain also requires plenty of oxygen, which is delivered via the bloodstream. This means that maintaining optimal blood supply is crucial for cognitive function, as this is how all the important nutrients and oxygen are delivered to the brain. 

But the brain requires extensive nutrients beyond the ones involved in energy production. From a structural perspective, nerves require a myelin sheath – the insulating layer of tissue that is made up of fats and proteins that acts as a conduit for electrical impulses – in order to transmit signals known as nerve impulses. Both folate (B9) and vitamin B12 are crucial for the synthesis of myelin, and thus these important B vitamins help make sure that the nerve cells in the brain can transmit signals rapidly and efficiently.

Fatty acids like omega-3s play crucial roles in the structural composition of neuronal cells. Their unique properties facilitate many membrane actions in the brain that other fatty acids aren’t able to achieve. One of the primary omega-3’s, DHA, also helps with the synthesis of phosphatidylserine (PS), which helps with many aspects of neuronal cell health, including survival under stress. Because humans are not very good at synthesizing the long chain omega-3 fatty acids themselves, they need to be obtained through the diet. 

The communication of signals in the brain are also heavily dependent on neurotransmitters, which are chemical messengers that can either be excitatory or inhibitory. Many neurotransmitters are synthesized from amino acids (the building blocks of proteins) in multistep processes that require B vitamins including B9, B6, and B12. The pyridoxal 5’-phosphate (P5P) form of vitamin B6 is especially important as it’s a required coenzyme for the synthesis of GABA, dopamine, norepinephrine and serotonin. Minerals, such as zinc, are also involved in helping neurotransmitters, including GABA, aspartate and norepinephrine, properly deliver their signals. 

The brain is a busy organ, with a high level of metabolism in its mitochondria. Because of its specialized structures, it contains many delicate pieces that can be easily damaged. Overall this means that the brain is almost constantly at risk of being damaged by its own metabolic by-products, in the form of reactive oxygen species (ROS). At low levels, ROS are thought to be benign or maybe even beneficial – and under normal circumstances, any excessive ROS produced during energy production is cleaned up by antioxidants in the cell. However, if insufficient antioxidants are present, this extra ROS production in the mitochondria can damage cellular structures within the mitochondria itslef, leading to mitochondrial dysfunction and damage to the delicate fats that comprise much of the brain's cellular structure. While the brain can produce some of its own antioxidants to protect against these compounds, modern research shows that polyphenols from foods help fight the inflammation caused by neutralizing free radicals and ROS.

Although food has long been perceived as a means to provide energy for the brain, our diet’s unique ability to provide nutrients that serve as essential building materials – from cofactors for metabolism to protection against oxidative stress – is increasingly being recognized. The brain requires a constant supply of micronutrients for energy metabolism of neurons and glial cells, neurotransmitter synthesis and action, nerve impulse propagation, and homocysteine metabolism. Without proper daily nutrition, any of these processes can be derailed. Nutrition is a foundational building block of brain health; what we eat matters.