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  • A new study finds that high-intensity interval exercises can help the brain and potentially protect against conditions like Alzheimer’s disease.
  • Research looking at whether exercise can prevent or slow the progression of Alzheimer’s disease, or boost memory in people with cognitive impairment, has been mixed.
  • Risk factors for heart disease and stroke including high blood pressure and diabetes can also impact brain health.

Six minutes of high-intensity interval exercise boosted the blood level of a protein involved in learning and memory formation, a new study found.

The protein, known as brain-derived neurotrophic factor (BDNF), is being explored as a potential therapy for neurodegenerative disorders, such as Alzheimer’s disease and Parkinson’s disease.

So far, no clinical trial has shown that delivering BDNF to the brain can slow or prevent the loss of neurons of people affected by Alzheimer’s disease.

However, some studies have found that exercise can improve blood flow or brain connectivity — and possibly memory — in people with mild cognitive impairment (MCI), although the research has been mixed.

Travis Gibbons, lead author of the new study and a PhD candidate in environmental physiology at the University of Otago, New Zealand, thinks exercise might provide a way to boost BDNF levels in the brain without the need for medical treatments.

“BDNF has shown great promise in animal models, but pharmaceutical interventions have thus far failed to safely harness the protective power of BDNF in humans,” he said in a press release.

Therefore, “we saw the need to explore non-pharmacological approaches that can preserve the brain’s capacity, which humans can use to naturally increase BDNF to help with healthy aging,” he added.

The study was published January 11 in The Journal of Physiology.

BDNF promotes neuroplasticity — the formation of new connections and pathways in the brain — and the survival of neurons. These are required for forming and storing memories and for overall cognitive performance.

Animal studies — such as a 2016 study in mice — show that increasing the level of BDNF in the brain can reduce or slow some of the damage caused by Alzheimer’s disease.

Similar studies have not yet been done in people. However, a phase 1 clinical trial by researchers at the University of California, San Diego, will use gene therapy to increase the level of BDNF in the brain of people with mild cognitive impairment or Alzheimer’s disease.

In the new study, Gibbons and his colleagues explored whether exercise or fasting could boost BDNF levels without the need for gene therapy.

Animal studies have shown that fasting has a similar effect as exercise on BDNF levels.

The researchers recruited 12 physically active, healthy participants (six men and six women) for two exercise sessions on a stationary bicycle — one after eating a light meal and the other after 20 hours of fasting.

The exercise sessions included both 90 minutes of light cycling and six minutes of high-intensity intervals on the bicycle.

Researchers found that the largest increase in the blood level of BDNF occurred after the high-intensity cycling intervals.

BDNF also increased after 90 minutes of light cycling, but fasting for 20 hours had no impact on BDNF levels.

While in mice, 9 hours of fasting is enough to increase BDNF levels, the researchers write that 20 hours of fasting may not be long enough to produce a similar effect in people.

Other studies have also found that exercise — including rowing — can increase blood levels of BDNF in people.

Rong Zhang, PhD, a professor of neurology and internal medicine at UT Southwestern in Dallas, said the new study is interesting, but pointed out that it is focused on the short-term effects of two exercise sessions.

He said there are many steps between this study and being able to show not only that exercise consistently boosts BDNF levels in the brain, but also that this can prevent or slow the progression of Alzheimer’s disease.

Research looking at whether exercise can prevent or slow the progression of Alzheimer’s disease, or boost memory in people with cognitive impairment, has been mixed.

“This is a very challenging question,” said Zhang, partly because of the limitations of clinical studies, such as the small number of participants and a short study duration.

In addition, researchers also have to examine many aspects of exercise, he said.

For example, can exercise benefit people who already have Alzheimer’s disease, or do people have to start exercising when they are younger?

Also, who will get the most benefit from exercise, and what type of exercise produces the best results?

Although these questions still need to be answered, “the accumulated evidence clearly suggests that what is good for the heart is good for the brain,” said Zhang.

Risk factors for heart disease and stroke — such as high blood pressure, diabetes, smoking, poor diet and physical inactivity — may also impact brain health, he said.

Some research has already shown that exercise has a positive effect on the brain.

“I think the most convincing evidence, at least in my mind, is that exercise can improve vascular health,” said Zhang. “This potentially can have an impact on the prevention of Alzheimer’s disease.”

In a study published in 2020 in the Journal of Alzheimer’s Disease, Zhang and his colleagues found that 12 months of aerobic exercise increased cerebral (brain) blood flow in people with mild cognitive impairment.

Another study showed that people with mild cognitive impairment who took part in a 12-week walking program saw increased connections between neurons in a part of the brain involved in memory.

However, a study published last year found that an 18-month exercise program did not boost episodic memory or executive function in people with no diagnosis of dementia.

In a press release, the researchers for this study said this doesn’t mean exercise won’t improve cognitive performance in older adults, just that it doesn’t appear to boost mental abilities in healthy people.

In addition, they pointed out that while the participants’ cognitive abilities didn’t improve over the course of the study, they also didn’t decline.

Zhang pointed out that another challenge with studying the impact of exercise on the brain is that it takes a long time for these benefits to accumulate.

Some clinical trials may not last long enough to pick up on these cumulative changes.

This also suggests that if you want to boost your mental health, you should start exercising earlier in your life and do it regularly.

“Exercise should be a habit,” said Zhang. “You should build that habit early on, starting in your childhood. That will definitely have an impact [on brain health.]”

However, that doesn’t mean you can’t start exercising later in life.

“There are clinical studies that suggest that older adults who start exercising clearly get benefits for cardiovascular health,” said Zhang.

“The impact of those benefits on brain health may take time,” he added. “But even if you start exercising late, there is a potential effect on the brain.”