Growing new brains cells is the stuff of science fiction, right?
Well, not exactly. It exists in the real world, with each and every one of us able to add neurons to our brain—an organ we once thought had a finite number of cells that had to last a lifetime.
Now, let’s not get too wild. The rate of adult neurogenesis (the growing of new brain cells) is nowhere near enough to keep up with the rate of decay, especially given it increases as we age. The human brain loses 5% of its volume per decade after the age of 40, and once we hit 70, that rate could increase again(1).
Of course, the ultimate goal would be to boost the rate of new cell growth in the brain to outstrip age-related decay. However, that’s a pipe dream. At least, as of 2018.
Fret not—plenty of research focused on boosting neurogenesis capabilities has been conducted, and in this article, we’ll delve into the science of 3 major factors (diet, exercise, and enriched environments) that have been proven to boost neuron growth in the brain.
As discussed in the previous article, adult neurogenesis is limited to the subgranular zone of the dentate gyrus in the hippocampus (SGZ) and the subventricular zone of the lateral ventricles (SVZ). Not much is known about why neural progenitor cells exist in these specific locations. It may be that the microenvironments of these areas are particularly conducive for neuronal growth.
What are the ingredients of the neuronal primordial soup? Neuronal growth factors (also known as neurotrophins) such as brain-derived neurotrophic factor (BDNF) are a vital instigator of neurogenesis. Neurotransmitters, especially monoaminergic ones (like serotonin) also modulate neuronal growth. This may explain why nerve growth is so drastically affected in psychiatric illnesses, which are marked by changes in neurotransmitter levels(2). Relatively unmodifiable factors such as epigenetic modulators (molecules that affect how your genes are expressed) and transcription factors (molecules that help translate your genetic code into proteins) are also part and parcel in determining our inherent ability to grow new neurons.
We are what we eat. Researchers have found that diet impacts adult neurogenesis based on 4 different aspects:
• the amount of calories we take in
• food frequency
• meal texture
• meal content
Firstly, limiting the food we eat has been known to have a positive effect on the brain, with studies demonstrating that fasting and calorie restriction enhance mood and protect against neurodegenerative disease. Reducing the calorie intake of rats by 30-40% resulted in an increase in adult hippocampal neurogenesis, an effect that appears to be related to an elevation of BDNF levels(3).
Even without reducing calorie intake, extending times between meals is thought to increase neurogenesis by altering gene expression(4). A more curious link that has been discovered is that eating solid food (as opposed to soft foods) may help boost neuron growth(5). Researchers think that the act of chewing is somehow related to alterations in cortisol levels, which is known to influence adult neurogenesis. That being said, can these findings be extrapolated out, explaining why neurogenesis is reduced in the elderly, who often have limited chewing abilities due to dental reasons? It’s interesting, but at this stage, unproven.
What we put in our body has far reaching effects—from our waistline to our brain—and eating less high-fat food improves both. Mice that were put on high-fat diets were found to have lower levels of BDNF in the hippocampus, reduced levels of neurogenesis and showed lower learning capabilities (6,7).
Moreover, the addition of dietary nutrients such as flavonoids(4) (found in cocoa), vitamin E(8) (in vegetable oil, leafy vegetables, and nuts), curcumin(9) (a type of curry spice) and (-)-epigallocatechin-3-gallate10 (EGCG – found in green tea) have all been linked to increased hippocampal neuron growth in mice.
As we’ve discussed in other posts, the benefits of exercise can’t be overstated. Exercise improves blood circulation to the brain, which in turn increases transport of nutrients and oxygen to the SGZ and SVZ. Neural growth factors like BDNF, serotonin, and insulin-like growth factor are also secreted in high amounts during exercise. Running is thought to increase neural growth by reducing the time cells need to multiply, promote neuron maturation and prevent the premature death of new neurons(11).
Interestingly, exercise duration, intensity, and even willingness to exercise modifies the response of neural stem cells(12). Exercising for longer periods promotes neuron differentiation and survival, while shorter durations stimulate an increase in cell number. Low to moderate exercise intensity is thought to improve neurogenesis in comparison to high-intensity exercise, as the latter is linked to a high-stress response that may mask its ability to promote neurogenesis.
Actually convincing yourself that you want to exercise may be a crucial step in stimulating neuron growth. Although adolescent rats that were forced to run on a treadmill had improved learning abilities, researchers found increased anxiety levels and decreased neural growth factor VEGF and BDNF levels in their brains13. As we all know, the hardest part of exercising is often mustering the willpower to do it!
Life experience has long been known to influence brain development. In scientific terms, this is known as an ‘enriched environment.’ It implies being surrounded with a variety of sensory and intellectual stimulation—from trying out new things and enjoying yourself to maintaining good social relationships.
Of course, it’s no surprise that a mentally positive environment imparts cognitive benefits, but the depth and breadth of the benefits may shock you. Improved learning and memory, reduced anxiety, and alleviating degenerative disease symptoms have all been shown to occur in enriched environments.
Mental stimulation does wonders to the brain – it increases neuronal size and number, synaptic density (the amount of connections between neurons in the brain which is correlated to cognitive reserves and decreased in dementias) and neurotrophin levels(14). Additionally, after maturing, a new brain cell needs to pass one last hurdle of integration before being able to survive. Much like in the animal kingdom, an enriched environment is also thought to increase the survival rate of newborn neurons.
In one study, mice that were reared in cages rich with learning opportunities (such as running wheels and mice tunnels that stimulated their cognitive abilities) were found to have a higher number of new neurons in the hippocampus after spending just a week in these conditions(15). Furthermore, researchers found that repeated exposure to the same learning conditions within 3 weeks of the first exposure appeared to substantially increase the number of new neurons.
Having a healthy sex life may also be a contributor to neuronal growth. Rats that were allowed regular copulation opportunities displayed more neurons in their hippocampus and displayed reduced levels of anxiety—although the key seems to lie in it being a long-term arrangement, as acute sexual experience in rats resulted in increased release of stress-related hormone and cortisol(16).
Last but not least, research has revealed fascinating insights into the effects of hallucinogenics on the brain. Both marijuana and psilocybin have been associated with increased neurogenesis(17,18). Marijuana is thought to act on the naturally occurring receptor, cannabinoid-1, which is displayed on neural stem cells. On the other hand, psilocybin, (the active ingredient in ‘magic mushrooms’) acts on serotonin receptors (5-HT2A receptors) that are also present on hippocampal neurons. However, lysergic acid diethylamide (LSD) did not appear to have any neurogenic effects.
To conclude this series on neurogenesis, it’s important to emphasize that every individual is different and that nerve growth is highly dependent on the cumulative effect of many different environmental and genetic factors. Some may respond terrifically in certain situations, while others may not experience any effects at all.
Here at GENEius, we have something that could help. Knowing our genetic makeup could help us focus our efforts on the changes that make the biggest difference. Click here to learn more about how our programs help you do exactly that, whether you’re a young professional or retiree.