Longevity Briefs: Is This The Best Exercise For Brain Health?

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: BDNF stands for brain-derived neurotrophic factor – brain-derived because it’s produced in the brain, and neurotrophic meaning that it promotes the growth and survival of new neurons and synapses. As you might expect for a molecule that grows brain cells, BDNF is important in learning and memory, but also seems to protect against inflammation in the brain, a key player in neurodegenerative disease. Levels of BDNF decline with age, but it seems that BDNF synthesis can be increased through lifestyle changes, particularly calorie restriction diets and exercise.

What did the researchers do: In this study, researchers wanted to look more closely at what practices were linked to the greatest increase in BDNF levels in the blood. They recruited 12 healthy participants, half male and half female, aged between 20 and 40. Participants visited the lab multiple times and either ate normally or fasted for 20 hours prior. At the lab, participants performed 90 minutes of light exercise followed by 6 minutes of high intensity interval training. Researchers measured BDNF levels in participants’ blood (BDNF can enter the blood from the brain, though some other tissues can also produce BDNF, including the blood vessel walls themselves).

Since most BDNF in the blood is carried by platelets, the researchers had to measure platelet BDNF and ‘free’ BDNF separately. This is important because the concentration of platelets in the blood can increase during exercise.

Key takeaway(s) from this research:

• High intensity interval exercise (regardless of fasting) was associated with the biggest increase in BDNF: a 3-fold increase over baseline.
• BDNF increased during the first 30 minutes of light exercise, but this was entirely due to an increase in the concentration of platelets in the blood.
• By the end of the 90 minutes of light exercise, free BDNF not bound to platelets did increase slightly.
• These increases were probably due to BDNF synthesis by the brain and release from platelets, not by the walls of the blood vessels.
• Fasting for 20 hours did not affect free BDNF levels in the absence of exercise, nor did it amplify BDNF increases during exercise.

So, it seems as though brief high intensity exercise is far more effective at increasing BDNF levels than extended low intensity exercise, which must continue for a long time in order to have even a modest effect. Based on previous animal studies as well as their own measurements, the researchers think that these BDNF increases were a combination of existing BDNF released by platelets and new BDNF synthesised in the brain.

Interestingly, fasting for 20 hours didn’t seem to affect BDNF, contrary to what has been found in animals. BDNF production during fasting is related to the delivery of ketone bodies to the brain, a type of fuel that the body produces when carbohydrates are scarce. It could simply be that the participants didn’t fast for long enough and didn’t reach a deep enough stage of ketosis to affect BDNF production.

Of course, this doesn’t mean that 20 hour fasting is not beneficial, nor that brief high intensity exercise is best for general health or even for overall brain health – simply that it seems to be the most efficient strategy for increasing BDNF in the short term. The relationship between exercise and brain function is complicated and much more research is needed to fully understand the merits of different types of exercise.