- William Lopez Lluc
- The Conversation*
“Healthy men in a healthy body”. We often use this quote to claim the beneficial effect of physical activity on mental abilities. Actually, the phrase appeared in Satire X written by the Roman comedian Juvenal back in the second century and was longer: it indicated that one had to pray to have a healthy spirit in a healthy body (“orandum est ut sit mens sana in healthy body”).
But is it true that keeping the body healthy, balanced and exercised helps maintain the mental capacities of our brain? Yes, and there is plenty of scientific evidence to prove it, especially when it comes to aging.
The brain loses volume during aging.
As we age, tissues and organs degenerate. The ability to maintain the functionality of the cells decreases and that is accompanied by a loss of tissue. It also occurs in the brain, with the consequent neurodegeneration or loss of neurons.
Whether in pathologies such as Alzheimer’s disease or in the loss of functionality due to aging, different changes associated with loss of function occur in the brain. Among them, thinning of the cortical area, loss of gray (neuronal bodies) and white (nerve conduction) tissue, increased volume of the ventricles (holes inside the brain where the cerebrospinal fluid is) and decrease in neurons in different areas, especially in the hippocampus.
In a longitudinal study involving hundreds of volunteers for years, the Baltimore study, it has been shown that the reduction in metabolic capacity associated with aging is related to the increase in the volume of the cerebral ventricle – the “hollow” space of the brain -. And that leads to a increased neurodegeneration and atrophy of the thinking organ.
If reducing metabolic capacity implies loss of brain volume, we can deduce that a better use of energy through exercise could slow down the loss of tissue in the brain.
More exercise, more memory
Is it so? Answering it is not easy. Above all, because one of the main obstacles that we find when determining the effect of any intervention on the brain is the practical impossibility of quickly verifying its consequences.
The brain is not like blood or muscle, which quickly show an easily measurable response directly or from blood components. The good news is that the advent of increasingly reliable imaging methods is making it possible to detect some structural changes in certain areas of the brain.
We have had evidence for a long time that the practice of physical exercise improves cognitive capacity and increases the size of certain areas of the brain, especially those related to memory.
For example, in 2011 an article was published in PNAS (Paper of the US National Academy of Sciences) indicating that physical exercise increases the volume of the hippocampus, the section of the brain where memory resides. Other studies in older people showed that physical exercise also prevented volume loss in this area of the brain.
On the other hand, the practice of controlled physical exercise in a population of elderly people has brought to light that there is a positive correlation between the practice of physical exercise and the amount of gray matter in other areas of the brain that are sensitive to degeneration associated with aging.
We tend to think of our body as a compartmentalized system. If we have a liver problem, we focus on the liver, and if it is on the kidney, then on the kidney. But our body doesn’t work like that: everything is interconnected. That is why a kidney problem can end up aggravating heart disease, or a liver problem can cause cerebral ischemia. In aging in particular, the complex body balances are in a very precarious situation.
When we exercise we put our body under moderate stress, as we force the cells to increase energy expenditure. This implies mobilizing nutrients, which must pass from the stores to the muscles. All the physiological changes necessary to cope with this moderate stress are known as hormesis.
In the process of hormesis, the muscles release substances that inform the rest of the organs that energy demand is increasing. These substances are called myokines and are released into the blood, which distributes them to the rest of the organs.
Some of these myokines reach the brain and there induce the expression of genes and proteins that increase the ability of neurons to establish new connections or strengthen existing ones.
One of these myokines is called BDNF (brain-derived neurotrophic factor), essential for neurons to establish connections and thus keep them active. In this simple way we can explain why physical exercise maintains brain volume during aging.
On the other hand, physical exercise also increases blood flow and oxygenation, which has a positive impact on brain activity also in older people. Furthermore, other studies have shown that moderate physical exercise produces anti-inflammatory effects that can generate effects in the brain, for example, thus reducing the progression of Alzheimer’s or senile dementia.
Scientific evidence, both direct and indirect, makes it clear that practicing physical activity as you age helps prevent brain degeneration, giving full meaning to the phrase “mens sana in corpore sano”.
It is better for us to avoid inactivity and a sedentary lifestyle if we want to add life to years and not just years to life.
*Guillermo López Lluch is a professor and researcher at the Andalusian Center for Developmental Biology and a researcher in metabolism, aging and immune and antioxidant systems at the Pablo de Olavide University in Seville. His article was published in The Conversation whose original version you can read here.
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