By Dr. Mercola
Many studies have confirmed that exercise helps prevent cognitive decline and staves off dementia. According to research published in the journal Neurology, moderate to intense exercise can slow brain aging by as much as 10 years!1,2,3 But what is it about moving your body that helps you maintain sharp brain function?
Researchers have discovered a number of different mechanisms behind this body-brain link. One, perhaps key, factor is how exercise affects brain-derived neurotrophic factor (BDNF), which is found in both your muscles and your brain.
Exercise Preserves and Grows Brain Matter
Exercise initially stimulates the production of a protein called FNDC5. This protein in turn triggers the production of BDNF, which is a remarkable rejuvenator in several respects. In your brain, BDNF:
- Preserves existing brain cells4
- Activates brain stem cells to convert into new neurons
- Promotes brain growth, especially in the hippocampus area; a region associated with memory
In one study, exercising mice grew an average of 6,000 new brain cells in every cubic millimeter of hippocampal tissue sampled,5 and in another,6 seniors who walked 30 to 45 minutes, three days per week for one year, increased the volume of their hippocampus by 2 percent.
Typically, your hippocampus tends to shrink with age. The results prompted the authors to claim exercise is "one of the most promising non-pharmaceutical treatments to improve brain health."
Exercise, Glucose Depletion and Brain Health
Your brain can use both glucose and fat for fuel, but the latter is preferred. When glucose is depleted from exercise, your hippocampus switches over to use fat as a source of energy, and it is this fuel switchover that triggers the release of BDNF and subsequent cognitive improvement.
This may also help explain why intermittent fasting and a high-fat, low-net carb diet have been shown to produce similar benefits for cognition and brain health as exercise.
Yet another mechanism at play here relates to a substance called β-hydroxybutyrate, which your liver produces when your metabolism is optimized to burn fat as fuel.9
When your blood sugar level declines, β-hydroxybutyrate serves as an alternative source of energy. However, β-hydroxybutyrate also blocks histone enzymes that inhibit the production of BDNF. So it seems your body is designed to improve BDNF production via a number of different pathways in response to physical exercise.
As mentioned, BDNF also expresses itself in your neuromuscular system. Here, it protects your neuromotor — which is the most critical element in your muscle — from degradation. Without the neuromotor, your muscle is like an engine without ignition.
Neuromotor degradation is part of the process that explains age-related muscle atrophy. So BDNF is actively involved in both your muscles and your brain, and this cross-connection helps explain why a physical workout can have such a beneficial impact on both muscle and brain tissue.
It, quite literally, helps prevent and even reverse brain decay as much as it prevents and reverses age-related muscle decay. Physical exercise also affects a number of other chemicals associated with brain health.
Exercising 4 Hours Post-Learning Boosts Long-Term Memory Retention
Recent research shows that exercising four hours after learning something new helps you retain what you've just learned long-term. The same effect was not found when the exercise was done immediately after learning.10,11
Why this four-hour delay boosted memory retention is still unclear, but it appears to have something to do with the release of catecholamines, naturally occurring chemicals in your body known to improve memory consolidation.
These include dopamine and norepinephrine. One way to boost these catecholamines is through exercise, and apparently delayed exercise is part of the equation.
Other Mechanisms by Which Exercise Boosts Brain Health
The connections between your physical fitness and your brain health run deep. Other mechanisms by which exercise protects and boosts your brain health include the following:
✓ Normalizing insulin resistance
Exercise is one of the most effective ways to normalize your insulin level and lower your risk of insulin resistance. In addition to lowering your risk for diabetes, this also helps protect your cognitive health, as diabetes is linked to a 65 percent increased risk of developing Alzheimer's.12
In addition to regulating your blood sugar level, insulin actually plays a role in brain signaling as well. When researchers disrupted the proper signaling of insulin in the brain, it resulted in dementia.13
✓ Improving and increasing blood flow to your brain
Your brain needs a significant supply of oxygen to function properly, which helps explain why what is good for your heart and cardiovascular system is also good for your brain. The increased blood flow that results from exercise allows your brain to almost immediately function better. As a result, you tend to feel more focused after a workout, which can improve your productivity at work and at home.
✓ Reducing plaque formation
By altering the way damaging proteins reside inside your brain, exercise may help slow the development of Alzheimer's disease. In one animal study, significantly fewer damaging plaques and fewer bits of beta-amyloid peptides, associated with Alzheimer's, were found in mice that exercised.14
✓ Decreasing Bone morphogenetic protein (BMP)
BMP slows down the creation of new neurons, thereby reducing neurogenesis. If you have high levels of BMP, your brain grows slower and less nimble. Exercise reduces the impact of BMP, so that your adult stem cells can continue performing their vital functions of keeping your brain agile. In animal research, mice with access to running wheels reduced the BMP in their brains by half in just one week.15,16
✓ Boosting Noggin
Exercise also results in a notable increase in another brain protein called Noggin, which acts as a BMP antagonist. So exercise not only reduces the detrimental effects of BMP, it simultaneously boosts the more beneficial Noggin as well. This complex interplay between BMP and Noggin appears to be a powerful factor that helps ensure the proliferation and youthfulness of your neurons.
✓ Lowering inflammation
✓ Boosting neurotransmitters associated with mind and mood
Exercise also boosts natural "feel good" hormones and neurotransmitters associated with mood control, including endorphins, serotonin, dopamine, glutamate and GABA.
A study by Princeton University researchers revealed that exercising creates new, excitable neurons along with new neurons designed to release the GABA neurotransmitter, which inhibits excessive neuronal firing, helping to induce a natural state of calm.18 The mood-boosting benefits of exercise occur both immediately after a workout and continue on in the long term.
✓ Metabolizing stress chemicals
Researchers have also teased out the mechanism by which exercise helps reduce stress and related depression — both of which are risk factors for dementia and Alzheimer's disease. Well-trained muscles have higher levels of an enzyme that helps metabolize a stress chemical called kynurenine. The finding suggests that exercising your muscles helps rid your body of harmful stress chemicals.19
Age-Related Cognitive Decline Is Not a Given
Ideally, you'd want to make exercise a regular part of your life from as early on as possible. But it's never too late to start. Even seniors who take up a fitness regimen can improve their cognitive function. For example, a team at the University of Edinburgh followed more than 600 people, starting at age 70, who kept detailed logs of their daily physical, mental and social habits.
Three years later, their brains were imaged for age-related changes, such as brain shrinkage and damage to the white matter, which is considered the "wiring" of your brain's communication system. Not surprisingly, seniors who engaged in the most physical exercise showed the least amount of brain shrinkage.20
Strength training — and working your leg muscles in particular21,22,23,24 — appears to have a particularly strong impact on brain function and memory. In one study, just 20 minutes of leg strength exercises enhanced long-term memory by 10 percent.25,26
Having an active lifestyle is really an investment in your future well-being, both physically and mentally. I believe that overall, high-intensity interval training really helps maximize the health benefits of exercise, while simultaneously being the most efficient and therefore requiring the least amount of time. That said, a varied and well-rounded fitness program that incorporates a wide variety of exercises is your best bet.
I also strongly recommend avoiding sitting as much as possible and walking more every day. A fitness tracker can be very helpful for this. I suggest aiming for 7,000 to 10,000 steps per day, in addition to your regular fitness regimen, not in lieu of it.
The science is really clear on this point: you do not have to lose your mind with advancing age. Your brain has the capacity to regenerate and grow throughout your life, and exercise is a really potent strategy that can help ensure your brain continuously rejuvenates with each passing year.