By Dr. Mercola
Researchers have suggested that exercise is "the best preventive drug" for many common ailments, from psychiatric disorders to heart disease, diabetes and cancer.1 Even your risk for age-related hearing loss is reduced through exercise.2 Physical fitness has also been linked to brain health, and is an important adjunct strategy to prevent dementia.
In fact, compelling evidence shows that physical exercise helps build a brain that not only resists shrinkage, but increases cognitive abilities3 and creativity. Researchers at Stanford University found that walking can increase creativity up to 60 percent.4,5 Even a casual stroll around your office can be helpful when you’re short on solutions.
Even more importantly, we now know that exercise promotes a process known as neurogenesis, i.e., your brain’s ability to adapt and grow new brain cells, regardless of your age. Exercise also promotes mental health by normalizing insulin resistance and boosting natural “feel good” hormones and neurotransmitters associated with mood control, including endorphins, serotonin, dopamine, glutamate and GABA.
Most recently, Canadian researchers found high-intensity workouts helped boost memory by improving hippocampal function6,7,8 — a finding they say could prove to be an important prevention strategy against Alzheimer’s disease, the most serious and deadly form of dementia. A recent scientific review9 also concluded that aerobic exercise increases left hippocampal volume, which also benefits specific memory functions.
High-Intensity Workouts Boost Memory
The Canadian study10 assigned 95 healthy young adults to one of three groups. One group completed six weeks of high-intensity interval training (HIIT) plus cognitive training, the other treatment group did HIIT only, while the control group remained inactive and got no cognitive training. Both HIIT groups experienced significant improvements in high-interference memory.
Interference memory refers to a process where data you’ve already memorized interferes with your ability to learn and memorize new information. Having good interference memory means you’re able to seamlessly integrate new information, enabling you to distinguish the new from the old.
One example of this type of memory is the ability to distinguish a new car of the same make, model and color as your old one. Interestingly, the exercise did not improve general recognition performance, a finding the researchers chalk up to the hypothesis that HIIT “selectively increases high-interference memory that may be linked to hippocampal function.”
Fitness Response Appears to Go Hand in Hand With Brain Benefits
Those who reaped the greatest improvements in fitness also had more significant increases in brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1. BDNF is a protein that has rejuvenating effects on both your muscles and your brain. High BDNF levels have also been correlated to a dramatic reduction in Alzheimer's risk, as it helps you grow new brain cells and protect old ones from deterioration.
As one would expect, those who participated in both HIIT and cognitive training saw the greatest improvements in memory in this study, and “high responders to exercise,” meaning those who gained the greatest fitness improvements, gained the greatest memory improvements of all.
According to the authors, this suggests “potential synergistic effects might depend on the availability of neurotrophic factors.” Indeed, the fact that BDNF is actively involved in both your muscles and your brain is thought to be a major part of the explanation for why physical workouts can have such a beneficial impact on your brain tissue.
Exercise Also Increases Mitochondrial Biogenesis in Your Brain
Other research has shown that, besides boosting BDNF and promoting neuroplasticity, exercise also increases an important metabolic signal called peroxisome proliferator-activated receptor gamma coactivator (PGC-1α), which increases mitochondrial biogenesis. The PGC-1α pathway regulates both mitochondrial activity and mitochondrial replication. This is important, as your brain is the most mitochondrially dense organ in your body. As noted by neurologist Dr. David Perlmutter in a previous interview:11
"[M]itochondria do more than just help us produce energy and power our cells. Mitochondria are actually involved in determining which cell lives or dies … This is mitochondrial therapy. We're now looking upon Alzheimer's and Parkinson's as acquired mitochondropathies or mitochondrial diseases that can be acquired by exposure to toxins, like we see with Parkinson's, or just direct toxic effects on mitochondria based upon diet.
For example, a high sugar diet is toxic to mitochondria. Here is yet [another] benefit to aerobic exercise that has just been published. It now looks as if those who engage in aerobic exercise have a wider diversity of gut bacteria. The more exercise you do, the more diverse are the organisms that live in your gut. That correlates with better health, reduced inflammation and a more balanced immune system."
Cardio Helps Grow a Bigger Brain
The second study, a meta-analysis12 of 14 controlled trials examining the effect of aerobic exercise on hippocampal volume in humans, found it had “significant positive effects on left hippocampal volume in comparison to control conditions.” It did not, however, have a significant effect on total hippocampal volume. According to Joseph Firth, Ph.D., research fellow at Australia’s National Institute of Complementary Medicine:13
“Our data showed that, rather than actually increasing the size of the hippocampus per se, the main 'brain benefits' are due to aerobic exercise slowing down the deterioration in brain size. In other words, exercise can be seen as a maintenance program for the brain."
The participants, 737 people in all, ranging in age from 24 to 76, included both healthy people and those with mild dementia or mental illness such as depression or schizophrenia. Exercise routines included a variety of cardio exercises, such as stationary cycling, walking and running, and were performed anywhere from two to five times a week for three months up to two years.
Your left and right hippocampi — one on each side of your brain — are part of your limbic system and play important roles in spatial navigation and the consolidation of short-term memory into long-term memory storage. Your hippocampus is also a major site where neuroplasticity occurs. Your left hippocampus is primarily involved in the memorization of names, and mediates the verbal memory function, while the right hippocampus is involved in nonverbal memory functions and spatial relationship memories.
According to the authors,14 “Post-hoc analyses indicated effects were driven through exercise preventing the volumetric decreases which occur over time. These results provide meta-analytic evidence for exercise-induced volumetric retention in the left hippocampus. Aerobic exercise interventions may be useful for preventing age-related hippocampal deterioration and maintaining neuronal health.”
Exercise Triggers Neurogenesis
The idea that your brain can rejuvenate and regenerate itself throughout your life is completely contrary to what I was taught in medical school. At that time, it was believed that once neurons die, there’s no turning back. As a result of this flawed understanding, memory decline was considered a more or less inevitable part of aging. Today we know that’s simply not true.
The key, however, is being proactive. Eating a healthy diet of real food — paying careful attention to getting sufficient amounts of healthy fats, including and especially animal-based omega-3 fats — and staying physically active lays the groundwork for healthy brain function as you age. As noted by psychiatrist Dr. John J. Ratey in his book “Spark: The Revolutionary New Science of Exercise and the Brain,” there’s overwhelming evidence showing that exercise produces large cognitive gains and helps fight dementia.
The studies above are not the only ones showing exercise boosts gray matter in the hippocampal region. A 2013 study15 found the total minutes of weekly exercise correlated with volume of the right hippocampus, meaning the more exercise people got, the larger their right hippocampus — the area associated with nonverbal memory functions and spatial relationship memories.
Exercise also preserves gray and white matter in your frontal, temporal and parietal cortexes, thereby preventing cognitive deterioration.16,17 In a 2012 study,18 those who exercised the most had the least amount of brain shrinkage over a follow-up period of three years.
A Fit and Healthy Lifestyle Protects Against Dementia, Even if You’re at High Risk
A 2015 randomized controlled trial19,20 published in The Lancet also demonstrated how a comprehensive prevention program can reduce the risk of dementia in those who are at high risk. Here, 1,260 adults in Finland, aged 60 to 77 years old, participated in the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability. Half were randomly assigned to the intervention group while the other half served as controls.
All were at high risk of dementia. The intervention consisted of regular meetings over the two-year trial period with various health professionals to address diet, exercise, brain training exercises and metabolic risk factors. At the end of two years, the intervention group scored 25 percent higher overall on the Neuropsychological Test Battery (NTB) — a standard test to evaluate mental functioning — than the control group. They scored even higher on certain parts of the test. As reported by Science Daily:21
“[F]or executive functioning (the brain's ability to organize and regulate thought processes) scores were 83 percent higher in the intervention group, and processing speed was 150 percent higher.
According to professor [Miia] Kivipelto, ‘Much previous research has shown that there are links between cognitive decline in older people and factors such as diet, heart health, and fitness. However, our study is the first large randomized controlled trial to show that an intensive program aimed at addressing these risk factors might be able to prevent cognitive decline in elderly people who are at risk of dementia.’"
Other Mechanisms by Which Exercise Boosts Brain Health
The connections between your physical fitness and your brain health run deep. I’ve already mentioned a few mechanisms for this connection, such as normalizing insulin sensitivity (which helps protect your cognitive health as diabetes is linked to a 65 percent increased risk of developing Alzheimer's22) and boosting BDNF, which plays an important role in the regeneration of neurons. Here are a few more:
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.23
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.24,25
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.
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.27 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.28
It’s Never Too Late to Benefit From Exercise
There’s no denying that exercise can have a profound impact on your health, and a major part of its benefit lies in its ability to prevent disease. Dementia and cancer are but two in an inordinately long list of health problems that can arise as a result of chronic inactivity. Your metabolic and cardiovascular health is also largely dependent on exercise.
Ideally, you’ll want to establish a comprehensive exercise program that includes high-intensity exercises and strength training — both of which have been shown to be of particular benefit for the prevention of dementia.
I also urge you to consider walking more, in addition to your regular workout regimen. Ideally, aim for 7,000 to 10,000 steps per day, and try to limit your sitting to three hours a day or less. Naturally, if you have a chronic disease, you will need to tailor your exercise routine to your individual circumstances, taking into account your fitness level and current health.
If your immune system is severely compromised, you may want to exercise at home instead of visiting a public gym. But exercise will ultimately help to boost your immune function, so it's important to continue with your program even if you suffer from chronic illness.
Needless to say, while it's never too late to start exercising, the earlier you begin and the more consistent you are, the greater your long-term rewards. Having an active lifestyle is really an investment in your future well-being, both physically and mentally. I believe that, overall, HIIT really helps maximize the health benefits of exercise, while simultaneously being the most efficient and therefore requiring the least amount of time.
That said, your best bet is to develop a varied and well-rounded fitness program that incorporates a wide variety of exercises. Remember, 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 the entire human life span, and exercise is perhaps the most potent way to ensure your brain’s continued growth and rejuvenation.