By Dr. Mercola

Scientists have been linking the benefits of physical exercise to brain health for many years, but new research is making it clear that the two aren't just simply related; rather, it is THE relationship.

As reported by The New York Times, new evidence shows that physical exercise helps you build a brain that not only resists shrinkage, but increases cognitive abilitiesi.

A study of mice produced a powerful illustration of just how influential physical exercise is on your brainii.

The mice were divided into four groups that included a group that had plenty of access to stimulating and sensual activities.

But only one group had a running wheel in their cages—and when the cognitive tests were completed, it turned out that being able to use the running wheel was the only thing that mattered in determining how well they did on the tests.

According to the New York Times:

"Animals that exercised, whether or not they had any other enrichments in their cages, had healthier brains and performed significantly better on cognitive tests than the other mice.

Animals that didn't run, no matter how enriched their world was otherwise, did not improve their brainpower in the complex, lasting ways that Rhodes's team was studying.

"They loved the toys," Rhodes says, and the mice rarely ventured into the empty, quieter portions of their cages.

But unless they also exercised, they did not become smarter."

How Does Exercise Affect Brain Power?

Exercise encourages your brain to work at optimum capacity by causing your nerve cells to multiply, strengthening their interconnections, and protecting them from damage. There are multiple mechanisms at play here, but some are becoming more well-understood than others.

For example, a number of animal studies, including the featured rodent study, have demonstrated that during exercise, the animals' nerve cells release proteins known as neurotrophic factors. One in particular, called brain-derived neurotrophic factor or BDNF, activates brain stem cells to convert into new neurons. BDNF also triggers numerous other chemicals that promote neural health. Further, exercise provides protective effects to your brain through:

- The production of nerve-protecting compounds
- Greater blood flow to your brain
- Improved development and survival of neurons
- Decreased risk of heart and blood vessel diseases
- Altering the way damaging proteins reside inside your brain, which appears to slow the development of Alzheimer's disease. In animal studies, significantly fewer damaging plaques and fewer bits of beta-amyloid peptides, associated with Alzheimer's, were found in mice that exercised

The Mechanism that Rejuvenates Your Brain Tissue

The featured New York Times article focuses on the rejuvenating effect of BDNF, and there's good reason for that. While scientists are not able to directly observe these effects in human brains, they have found that humans tend to have higher levels of BDNF in their bloodstream after working out, so there's reason to believe the effects found in animal research are also applicable to humans.

Growing evidence indicates that both fasting and exercise trigger genes and growth factors that recycle and rejuvenate your brain and muscle tissues. These growth factors include BDNF, as just mentioned, and muscle regulatory factors, or MRFs. These growth factors signal brain stem cells and muscle satellite cells to convert into new neurons and new muscle cells respectively. Interestingly enough, BDNF also expresses itself in the neuro-muscular system where it protects neuro-motors from degradation. (The neuromotor is the most critical element in your muscle. Without the neuromotor, your muscle is like an engine without ignition. Neuro-motor 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, if you will, appears to be a major part of the explanation for why a physical workout can have such a beneficial impact on your brain tissue. It, quite literally, helps prevent, and even reverse, brain decay as much as it prevents and reverses age-related muscle decay.

This also helps explain why exercise while fasting can help keep your brain, neuro-motors, and muscle fibers biologically young. For more information on how to incorporate fasting into your exercise routine for maximum benefits, please see this previous article by fitness expert Ori Hofmekler.

Other Brain-Influencing Mechanisms Triggered by Exercise

Researchers at Northwestern University's Feinberg School of Medicine in Chicago have also discovered a couple of other mechanism that helps explain why exercise is so good for your brain.

It appears that exercise lowers the activity of bone-morphogenetic protein or BMP, which slows the production of new brain cells. At the same time, exercise increases Noggin, a brain protein that acts as a BMP antagonist. The more Noggin present in your brain, the less BMP activity there is, and the more stem cell divisions and neurogenesis (production of new brain cells) takes place.

According to a 2009 PLoS One study:

"Exposure to exercise or to environmental enrichment increases the generation of new neurons in the adult hippocampus and promotes certain kinds of learning and memory. While the precise role of neurogenesis in cognition has been debated intensely, comparatively few studies have addressed the mechanisms linking environmental exposures to cellular and behavioral outcomes. Here we show that bone morphogenetic protein (BMP) signaling mediates the effects of exercise on neurogenesis and cognition in the adult hippocampus. Elective exercise reduces levels of hippocampal BMP signaling before and during its promotion of neurogenesis and learning...

[R]educed BMP signaling is required for environmental effects on neurogenesis and learning... [T]hese observations show that BMP signaling is a fundamental mechanism linking environmental exposure with changes in cognitive function and cellular properties in the hippocampus."

Exercise and Emotional States

In addition to all of this, we can find further clues by looking at research on exercise for the treatment of depression. It works primarily by helping to normalize your insulin levels, while also boosting endorphin production—the "feel good" hormones in your brain. As Dr. James S. Gordon, MD, a world-renowned expert in using mind-body medicine to heal depression has said:

"What we're finding in the research on physical exercise is that exercise is at least as good as antidepressants for helping people who are depressed… physical exercise changes the level of serotonin in your brain. And it increases your endorphin levels, your "feel good hormones."

And also—and these are amazing studies—exercise can increase the number of cells in your brain, in the region of the brain called the hippocampus. These studies were first done on animals, and they're very important because sometimes in depression, there are fewer of those cells in the hippocampus. But you can actually change your brain with exercise. So it's got to be part of everybody's treatment, everybody's plan."

Nutrition and Brain Health

Another factor that cannot be overlooked is your diet. Foods have an immense impact on your body and your brain, and eating whole foods as described in my nutrition plan will best support your mental and physical health. Just like exercise, avoiding sugar (particularly fructose) and grains will help normalize your insulin levels. This is an important aspect, as sugar causes chronic inflammation that disrupts your body's normal immune function and can wreak havoc on your brain.

But sugar also suppresses BDNF, which is important for proper memory function, and appears to play a significant role in depression as well. At least we know that BDNF levels tend to be critically low in people with depression, and some animal models have suggested low BDNF levels may actually be causative.

So, when you consider all of these inter-connected metabolic pathways that are all affected by diet and exercise, it becomes rather easy to see why a low-sugar diet in combination with regular exercise can have such profoundly beneficial effects on memory and mental health!

Aim for a Well-Rounded Fitness Program

Ideally, to truly optimize your health, you'll want to strive for a varied and well-rounded fitness program that incorporates a variety of exercises. As a general rule, as soon as an exercise becomes easy to complete, you need to increase the intensity and/or try another exercise to keep challenging your body. I recommend incorporating the following types of exercise into your program:

1. High-Intensity Interval (Anaerobic) Training: This is when you alternate short bursts of high-intensity exercise with gentle recovery periods.

2. Strength Training: Rounding out your exercise program with a 1-set strength training routine will ensure that you're really optimizing the possible health benefits of a regular exercise program.
You need enough repetitions to exhaust your muscles. The weight should be heavy enough that this can be done in fewer than 12 repetitions, yet light enough to do a minimum of four repetitions. It is also important NOT to exercise the same muscle groups every day. They need at least two days of rest to recover, repair and rebuild.

You can also "up" the intensity by slowing it down. For more information about using super slow weight training as a form of high intensity interval exercise, please see my interview with Dr. Doug McGuff.

3. Core Exercises: Your body has 29 core muscles located mostly in your back, abdomen and pelvis. This group of muscles provides the foundation for movement throughout your entire body, and strengthening them can help protect and support your back, make your spine and body less prone to injury and help you gain greater balance and stability.
Exercise programs like Pilates and yoga are also great for strengthening your core muscles, as are specific exercises you can learn from a personal trainer.

4. Stretching: My favorite type of stretching is active isolated stretches developed by Aaron Mattes. With Active Isolated Stretching, you hold each stretch for only two seconds, which works with your body's natural physiological makeup to improve circulation and increase the elasticity of muscle joints. This technique also allows your body to repair itself and prepare for daily activity. You can also use devices like the Power Plate to help you stretch.