What Is BDNF?
Why Is It Important For Cognitive Function?
Brain Derived Neurotrophic Factor, often referred to as the acronym BDNF, is currently one of the most talked-about topics in the world of bio-hacking.
Several years ago, the only time you would come across the letters BDNF would be in a serious medical journal, or perhaps on some of the more obscure longevity-focused forums. Today, however, it is definitely a well known substance. You’ll find dozens of posts about BDNF on places like Reddit and Longecity.
So what is BDNF exactly?
Why is it such a hot topic in the nootropics world right now?
What does it do? Is it relevant to you? How can it be manipulated to help with cognitive function?
In the article below, I’ll try to answer all of these questions in as much detail as I can. I’ll start with a quick overview of what BDNF is, where it comes from, and what it does in the body. I’ll then take a look at some of the studies showing how BDNF can be manipulated, and what effects that can have. At the end, I’ll discuss some of the varied ways that people are trying to manipulate their BDNF levels.
If you finish the article and still have some questions, please post them in the comments section and I or another member of the team will get back to you asap!
What Is BDNF? What Does It Do?
As you probably worked out from the name, BDNF is a neurotrophic factor.
A neurotrophic factor is a molecule – typically a peptide – which regulates the growth, proliferation and differentiation of specific brain cells.
Most neurotrophic factors stimulate neuron growth and synapse plasticity, which is where synapses get ‘stronger’, more efficient and ‘healthier’ over time. Brain Derived Neurotrophic Factor is known to cause synaptogenesis – or the growth of new synapses – through the prevention of actin-capping (something we’ll come back to later).
BDNF’s primary role, however, is to ensure the survival of existing neurons, as well as to promote the growth and proliferation of new neurons.
It is primarily active in the hippocampus, although it can also be found in several different areas of the brain and peripheral nervous system, including basal forebrain, the cortex, retina, and even to some degree in the prostate.
Seeing as it is responsible for triggering neurogenesis (the growth of new neurons from brain stem cells) and seeing as it is found primarily in the hippocampus, it isn’t surprising that BDNF is thought to be hugely important for long-term memory formation, as well as for ensuring overall good cognitive function.
With that, it’s time we had a look at what kind of effect BDNF has on cognitive function, brain development, and overall brain health.
BDNF & Cognitive Decline
We’re not short of evidence showing that BDNF levels have a massive and direct effect on various different aspects of cognitive function.
The majority of the research looking at BDNF has focused on its relationship with pathological cognitive decline.
For example, take a look at this paper, published in the International Journal of Neuropsychopharmacology in 2011.
These researchers had no problem identifying the link between BDNF and the rate of cognitive decline in certain people: “We demonstrate that BDNF serum levels are significantly decreased in AD patients with fast cognitive decline compared to AD patients with slow cognitive decline and show a significant correlation with the rate of cognitive decline during 1 yr follow-up. These results suggest that higher BDNF serum levels are associated with a slower rate of cognitive decline in AD patients.”
Another study took a broader look at the picture. Here, researchers looked at subjects with different neurodegenerative processes and different intensities of cognitive impairment.
The results were strikingly similar: “We found significant correlation between BDNF serum levels and cognitive impairments. After multiple comparisons between the groups, we found that, after adjustment for confounding factors (age, gender, education, depression, cognitive impairment), BDNF serum levels were the lowest in Alzheimer’s Disease group”
More longitudinal studies are needed here obviously. It is also far from obvious from these results that BDNF is the main driver of Alzheimer’s Disease; it is an incredibly complicated condition, and it probably has multiple confounding causes.
Yet it is clear that Brain Derived Neurotrophic Factor expression is involved in the progression of neurodegenerative diseases in some way.
However, it isn’t simply a matter of low BDNF = faster cognitive decline. Different neurodegenerative diseases seem to be affected by BDNF in different ways.
Check out this fascinating paper, published in Biomedical Research International in 2013.
The findings of this study show that both higher and lower serum BDNF levels may promote the onset of different neurodegenerative disorders: “Our results evidenced lower BDNF serum levels in Alzheimer’s Disease, Frontotemporal Dementia, Lew body dementia, and vascular dementia patients and a higher BDNF concentration in patients affected by Parkinson’s Disease.”
This finding has been backed up by other studies, such as this one, first published in 2015: “In summary, subjects with cognitive impairment (AACD, MCI, and AD) had significantly higher serum BDNF levels than the normal control group in the present study.”
So what’s going on here?
How can some people with cognitive impairment display significantly lower levels of BDNF, and others significantly higher levels of serum BDNF?
Does that mean BDNF is incidental and not causal?!
No. I think there’s a very good explanation for these discrepancies.
Firstly, I need to point out that a majority of studies looking at BDNF and cognitive decline have found a correlation between lower serum levels and more severe or faster rates of cognitive impairment. This has been pointed out repeatedly by Johan Theorin, who researches nootropics for Open Health Tools. The inverse relationship between serum BDNF and cognitive function does not appear in the majority of clinical trials.
Secondly, it looks as though many of the studies showing a correlation between higher serum BDNF levels and cognitive decline have focused on subjects in the early stages of cognitive impairment. It may be that the body is trying to compensate for reduced synaptic or neuronal activity by increasing BDNF expression.
Indeed, the 2015 paper from Clinical Psychopharmacology and Neuroscience, cited above, states exactly this: “Increased serum BDNF levels have been observed in patients with MCI and early AD which supports the notion that there is possibly a compensatory augmentation of neurotrophin synthesis in the earliest stages of AD progression. In line with these findings, the present study found increased serum BDNF levels in subjects with cognitive impairment. This may be due to the high proportion of subjects in the relatively early stages of cognitive impairment in the present sample.”
A lot more work is needed here.
The studies discussed above DO NOT SHOW that lower (or indeed higher) BDNF levels cause cognitive decline.
They merely show that when people are experiencing serious cognitive decline, they tend to have lower levels of serum BDNF. They also seem to show that people with early stage Alzheimer’s Disease often have higher levels of serum BDNF.
This does not mean that raising BDNF necessarily guards against cognitive decline. It certainly doesn’t mean that you can avoid serious diseases like Alzheimer’s by simply raising BDNF levels.
BDNF & Cognitive Performance
There are few studies showing that elevating Brain Derived Neurotrophic Factor has a direct, immediate and positive influence on cognitive performance.
Most of the claims made by supplement manufacturers are limited to the more general, long-term benefits associated with having generally higher levels of BDNF (i.e reducing the rate of cognitive decline, promoting neuron growth, maximizing synapse health, etc).
However, there are some good clinical studies showing that BDNF levels can be acutely elevated, and that this usually accompanies improved cognitive performance in several different ways. Instead of just going through theory and conjecture, I’ll cite a few studies which you can look at in your own time.
This study took a group of 44 participants and got them to do various things known to increase BDNF expression, including mentally-demanding tasks and physical exercise.
The researchers found a “positive effect of mental training on the cognitive parameters, parallel with BDNF elevation”, which they say “suggests that mental training is a more useful, safe, and persistent strategy to attenuate the progression of MCI probably via BDNF elevation”.
It is important to note that the researchers explicitly record the elevation as small.
Other studies, such as this one, have suggested that BDNF needs to be present in sufficient quantities for the brain to properly process and encode memories. As the cited paper states: “Thus, our results indicate that endogenous BDNF is required for both STM and LTM formation of inhibitory avoidance learning, possibly involving CREB activation-dependent mechanisms.”
There is also now evidence suggesting that Brain Derived Neurotrophic Factor is involved in the different parts of the brain and the different stages of memory formation.
This makes intuitive sense. BDNF is the main regulator of synaptic activity and neuron formation. Its effect is usually gradual rather than acute, but that doesn’t mean that it can’t have a more immediate role in short-term memory function and long-term memory storage.
Short-term memory function relies on the effective function of various synapses and neurons.
Long-term memory storage is poorly understood, but it seems that it is likely dependent on the formation of new neurons.
As such, it makes sense that better overall memory function might be some of the immediate benefits one might experience from having healthy BDNF levels.
Can You Elevate BDNF Naturally?
As you might imagine from all of the exciting research discussed above, there’s a lot of interest right now in the possibility of raising Brain Derived Neurotrophic Factors levels naturally.
People see it as a way of enhancing both their long-term mental capabilities and their short-term cognitive performance. With good reason; while any claims about BDNF being a miracle cure for dementia or Alzheimer’s are outright lies, the claims that it might help attenuate cognitive decline and promote good overall cognition seems to have serious scientific backing.
So it shouldn’t surprise you to learn that there has been an explosion in BDNF-boosting supplements over the last few years. There’s also been a steep rise in the number of articles talking about various natural methods for raising BDNF expression.
But does any of it actually work?
Is it possible to boost BDNF naturally?
I think there is sufficient evidence to say that there are a number of different ways to significantly increase BDNF expression naturally.
Here are some of the most reliable ways to naturally increase BDNF levels.
The most reliable way to increase Brain Derived Neurotrophic Factor levels in the brain is to exercise. More specifically, aerobic exercise seems to significantly increase BDNF expression in the brain.
There is no shortage of studies demonstrating a positive relationship between BDNF and aerobic exercise.
A study published in the Journal of Sports Science & Medicine in 2013 found that running caused an average BDNF increase of 32%.
That’s not a typo – a 32% increase just from running.
The mechanism behind this relationship is not widely known. However, I have read one interesting paper which posited a very plausible explanation: “Here, we report that an endogenous molecule released after exercise is capable of inducing key promoters of the Mus musculus Bdnf gene. The metabolite β-hydroxybutyrate, which increases after prolonged exercise, induces the activities of Bdnf promoters, particularly promoter I, which is activity-dependent.”
That would explain why running in particular seems to boost BDNF; you need to do prolonged exercise rather than short and intense exercise to see benefits.
There are a number of supplements out there which are thought to boost brain derived neurotrophic factor, as well as other neurotrophic factors.
For example, Lion’s Mane Mushroom is known to significantly increase Nerve Growth Factor expression. This neurotrophic factor works in a very similar way to BDNF, promoting neuron growth and synapse differentiation. There is some evidence that cordyceps mushrooms can reliable boost brain derived neurotrophic factor release in the brain, but this is far from conclusive. We’ll cover this in another article!
DHA, the most important constituent of fish or algae oil, has also been shown to increase serum BDNF levels. Ensuring that you regularly consume DHA is probably one of the best ways to boost this amazing neurotrophic factor.
Other substances, such as bacopa monnieri and ashwagandha, are often said to boost Brain Derived Neurotrophic Factor. However, I’ve not seen enough evidence to say that this is likely true.
As if you didn’t already have enough reasons to fast on a regular basis!
Regular fasting has been show to reliable promote Brain Derived Neurotrophic Factor expression in humans.
Long fasts aren’t required; modest increases in Brain Derived Neurotrophic Factor levels in the brain have been observed in fasts of less than 24 hours.
This isn’t hearsay or hype – there’s lots of evidence showing that intermittent fasting promotes Brain Derived Neurotrophic Factor expression. Take this trial, for example. The researchers in this study concluded that ” intermittent fasting results in increased production of brain-derived neurotrophic factor (BDNF), which increases the resistance of neurons in the brain to dysfunction and degeneration in animal models of neurodegenerative disorders”.