This Is Why Aerobic Exercise Is 'Miracle-Gro' for Your Brain

Aerobic exercise increases BDNF which reduces dementia and improves cognition.

Posted Jun 06, 2016

Anton Balazh/Shutterstock
Source: Anton Balazh/Shutterstock

A study released this week offers more clues that help to explain why aerobic exercise is like 'Miracle-Gro' for the brain. Exercise has the power to increase cognitive functions and reduce your risk for dementia, anxiety, and depression

What makes exercise like Miracle-Gro? Brain-derived neurotrophic growth factor (BDNF) is a protein released during aerobic exercise which acts like neuron fertilizer. BDNF promotes neurogenesis (the growth of new neurons) as well as increased functional connectivity between brain regions via neuroplasticity.

A decade ago, when I published The Athlete’s Way (St. Martin’s Press), the idea of BDNF stimulating neurogenesis in the brain was a revolutionary concept. Luckily, while writing the manuscript for my book in 2005, I was able to speak with visionaries within the neuroscientific community who were trailblazers in identifying the connection between aerobic exercise, BDNF, and brain health. On p. 130, I wrote, 

"Exercise has been proven to promote neurogenesis by increasing BDNF (Brain Derived Neurotrophic Factor) and lowering cortisol. BDNF is responsible for making your neurons stronger. By increasing BDNF, exercise boosts your memory, making you smarter and happier.

BDNF is regulated by levels of serotonin and is known to be a prime candidate for causing serotonin delivering axon growth. Antidepressants work like exercise in that they increase BDNF, which may ultimately be why they are effective at elevating mood.”

Breaking a Sweat Makes Your Brain Bigger, Smarter, and Happier

 Rido/Shutterstock
Source: Rido/Shutterstock

Since I first wrote about exercise being like ‘Miracle-Gro’ for the brain because it stimulates the production of BDNF—there have been some advances that help to decode the mysteries of how this trophic factor operates on a molecular level.  

In 2013, Harvard researchers honed in on a specific molecule released during endurance exercise that improves cognition and protects the brain against degeneration. The study, "Exercise Induces Hippocampal BDNF Through a PGC-1/FNDC5 Pathway," appeared in the journal Cell Metabolism.

Through experiments conducted on mice, the investigators led by Dr. Bruce Spiegelman of the Dana-Farber Cancer Institute and Harvard Medical School found that a molecule called FNDC5 and its byproduct, irisin, become elevated in the brain through endurance exercise. The team also found that raising levels of irisin in the circulation caused the molecule to cross the blood brain barrier, which then increased the expression of BDNF and activated genes involved in cognition. On the other hand, mice genetically altered to have low irisin levels in the brain had reduced levels of BDNF.

Earlier this year, researchers in Finland confirmed that sustained aerobic activity—such as walking, jogging, biking, swimming, riding the elliptical trainer, etc.—has the power to increase the neuron reserve of the hippocampus via neurogenesis. 

The February 2016 study, "Physical Exercise Increases Adult Hippocampal Neurogenesis in Male Rats Provided It Is Aerobic and Sustained," was published in The Journal of Physiology. This study offers more proof about the power of aerobic exercise to optimize the structure and functional connectivity of the brain. 

How Is BDNF Produced During Aerobic Exercise?

 LANBO/Shutterstock
Source: LANBO/Shutterstock

This week, researchers from New York University (NYU) Langone Medical Center in Manhattan announced some exciting breakthroughs that help to better explain why sustained aerobic exercise benefits the mammalian brain on a molecular level. The June 2016 study, "Exercise Promotes the Expression of Brain Derived Neurotrophic Factor (BDNF) Through the Action of the Ketone Body β-Hydroxybutyrate,” appears in the journal eLife.

The researchers were fascinated by the innate desire of most mice to run on exercise wheels in the lab. For this study, they compared the brains of mice that had been allowed to run at will on an exercise wheel for a month with the brains of mice that didn't run. 

Laboratory chemical analyses of the mice brains were performed to determine molecular changes in BDNF production from exposure to HDAC inhibitors and DBHB. Genetic testing was also used to determine which genes were more active than others. These findings help to explain (at a molecular level) how the production of BDNF during exercise benefits a mammal's brain. In a statement, Moses V. Chao, senior investigator and cell biologist from the Chao Lab at NYU School of Medicine, said, 

"Our latest findings suggest how we might boost production of BDNF as studies have confirmed that doing so protects the brain. Other studies in people have already linked exercise, increased BDNF levels, and lower rates of dementia.  We believe that our study shows a precise biological mechanism behind increased BDNF production in mammals due to exercise. Unraveling the mysteries of BDNF is important as we seek more ways to naturally keep mammalian brains healthy."

Conclusion: Aerobic Exercise + BDNF = A Healthy Mind in a Healthy Body

Long before the advent of neuroscience, the Classical Greeks understood the connection between physical fitness and psychological well-being. The power of aerobic exercise to simultaneously create a healthy body and a healthy brain is summed up in the phrase mens sana in corpore sano (a sound mind in a sound body).

Hopefully, the latest findings on BDNF will motivate anyone who wants to maintain a sound mind in a sound body—by keeping his or her cardio-respiratory system and brain in good shape—to do some type of aerobic exercise for at least 20 minutes, most days of the week.

In addition to boosting the growth of new neurons and cognitive function, the latest research suggests that increasing BDNF production through aerobic exercise may ward off neurological disease throughout your lifespan.

To read more on this topic, check out my previous Psychology Today blog posts,

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