Neurogenesis: Can You Grow New Brain Cells?

For most of the 20th century, neuroscience had a dogma: “You’re born with all the neurons you’ll ever have. Neurons don’t regenerate.”

Damage your brain → permanent. Lose neurons with age → irreversible decline.

Then in 1998, a landmark study shattered this belief: Adult human brains grow new neurons—thousands per day—in specific regions, particularly the hippocampus.

This process is called neurogenesis, and it fundamentally changes how we think about brain aging, learning, and recovery.

The revolutionary insight: Your brain isn’t a fixed machine that degrades over time. It’s a dynamic, self-renewing organ that can grow new neurons throughout your entire life—if you create the right conditions.

The question isn’t whether you can grow new brain cells. The question is: Are you doing what it takes to trigger neurogenesis, or unknowingly suppressing it?

Let’s examine how neurogenesis works, where it happens, what controls it, and the evidence-based strategies that maximize new neuron growth.

What Is Neurogenesis?

Neurogenesis = the birth of new neurons (nerve cells) from neural stem cells.

The process:

1. Neural stem cells divide (in specific brain regions)
2. New cells migrate to their functional location
3. Immature neurons mature (grow dendrites, axon)
4. Integration into existing circuits (form synapses with neighbors)
5. Functional neuron (participates in information processing)

Timeline: 4-6 weeks from stem cell division to fully integrated, functional neuron.

Where Does Neurogenesis Happen?

In adult humans, neurogenesis is confirmed in two main regions:

1. Hippocampus (Dentate Gyrus)

Function:

• Memory formation (episodic and spatial memory)
• Learning new information
• Mood regulation (depression linked to reduced hippocampal neurogenesis)
• Pattern separation (distinguishing similar experiences)

Neurogenesis rate:

• ~700 new neurons per day in each hippocampus (left and right)
• ~1,400 total new hippocampal neurons daily (in healthy adults)

Significance: The hippocampus is critical for learning and memory. New neurons here enhance your ability to:

• Form new memories
• Learn complex information
• Distinguish similar experiences (pattern separation)
• Regulate mood and stress response

2. Olfactory Bulb (Smell Processing)

Function: Processing smell information

Neurogenesis rate: Thousands of new neurons daily

Relevance: Less cognitively significant for most people (unless you’re a sommelier or perfumer)

Debate: Other Regions?

Ongoing research investigates neurogenesis in:

• Striatum (movement, reward)
• Amygdala (emotion, fear)
• Cortex (some studies suggest minimal neurogenesis; others find none)

Current consensus: Hippocampal neurogenesis is well-established and functionally significant. Other regions remain controversial.

For cognitive function, hippocampal neurogenesis is what matters most.

What Controls Neurogenesis?

Neurogenesis isn’t constant—it’s highly regulated by your behaviors and environment.

The Master Regulator: BDNF

BDNF (Brain-Derived Neurotrophic Factor) is your brain’s growth fertilizer.

What BDNF does:

• Promotes stem cell division (more new neurons)
• Enhances neuron survival (prevents apoptosis)
• Stimulates synapse formation (better connectivity)
• Supports neuron maturation (faster integration)

Think of BDNF as:

• Miracle-Gro for your brain
• Without it: neurogenesis plummets
• With high levels: neurogenesis accelerates

The key insight: You can control BDNF levels through behavior. Increase BDNF → increase neurogenesis.

What Increases Neurogenesis

Evidence-based promoters:

1. Exercise (Most Powerful)

• Aerobic exercise increases BDNF by 200-300%
• Hippocampal neurogenesis doubles in animals (running wheels)
• Humans: 30-60 min cardio, 4-5x/week → measurable hippocampal growth in 3-6 months

2. Learning and Cognitive Challenge

• Learning new, complex skills stimulates neurogenesis
• Enriched environments (novelty, complexity) promote growth
• Mental stimulation enhances survival of new neurons

3. Sleep

• Deep sleep is when most neurogenesis occurs
• REM sleep supports neuron integration
• Sleep deprivation cuts neurogenesis by 50%+

4. Caloric Restriction / Intermittent Fasting

• BDNF increases during fasting (evolutionary adaptation)
• Ketones (produced during fasting) enhance neurogenesis
• Moderate restriction (not starvation) is key

5. Omega-3 Fatty Acids (DHA)

• DHA (from fish) is a key building block for neurons
• Promotes neurogenesis and neuron survival

6. Antidepressants (SSRIs)

• Increase hippocampal neurogenesis (part of their mechanism)
• Takes weeks (matches time for new neurons to mature)

7. Social Connection

• Positive social interaction increases BDNF
• Reduces stress (stress suppresses neurogenesis)

What Decreases Neurogenesis

Evidence-based suppressors:

1. Chronic Stress

• Cortisol (stress hormone) is toxic to stem cells
• Chronic stress can reduce neurogenesis by 50-80%
• Damages hippocampus structurally

2. Sleep Deprivation

• Cuts neurogenesis in half (one week of poor sleep)
• Impairs neuron integration

3. Aging

• Neurogenesis declines ~10% per decade after 30
• But never stops (even 70-90 year olds have neurogenesis if healthy)

4. Alcohol

• Chronic heavy drinking impairs neurogenesis
• Damages stem cells
• Moderate drinking: Minimal impact

5. High-Sugar Diet

• Inflammation from sugar suppresses neurogenesis
• Insulin resistance impairs BDNF signaling

6. Sedentary Lifestyle

• No exercise = low BDNF = minimal neurogenesis
• Sitting all day is neurotoxic

The Exercise-Neurogenesis Connection

Exercise is the single most powerful way to grow new neurons.

How it works:

The science:

• Aerobic exercise triggers muscle to release cathepsin B (signaling protein)
• Cathepsin B crosses blood-brain barrier
• Stimulates BDNF production in the brain
• BDNF promotes neurogenesis in hippocampus

The dose:

• 30-60 minutes, 4-5x per week
• Moderate intensity (60-80% max heart rate)
• Activities: Running, cycling, swimming, brisk walking

The results:

• Hippocampal volume increases 2% in 6 months (reverses 1-2 years of age-related shrinkage)
• Memory and learning improve
• Mood enhances (reduced depression, anxiety)

No other intervention comes close to exercise for neurogenesis.

Neurogenesis and Mental Health

Depression is linked to reduced hippocampal neurogenesis.

The neurogenic hypothesis of depression:

• Chronic stress → ↓ BDNF → ↓ neurogenesis → depression
• Antidepressants (SSRIs) → ↑ BDNF → ↑ neurogenesis → mood improves (over weeks)
• Exercise → ↑ BDNF → ↑ neurogenesis → mood improves

Why antidepressants take 4-6 weeks to work:

• New neurons take 4-6 weeks to mature and integrate
• Matches the timeline for antidepressant efficacy
• Suggests neurogenesis is part of the mechanism

Alternative interventions (that also boost neurogenesis):

• Exercise (as effective as SSRIs for mild-moderate depression)
• Meditation (increases BDNF, reduces stress)
• Therapy (CBT reduces stress, indirectly supports neurogenesis)

The implication: Neurogenesis isn’t just about memory—it’s about emotional resilience and mental health.

Neurogenesis and Aging

Neurogenesis declines with age, but never stops.

The decline:

• Age 20: ~700 new neurons/day per hippocampus
• Age 40: ~630 new neurons/day (-10%)
• Age 60: ~560 new neurons/day (-20%)
• Age 80: ~490 new neurons/day (-30%)

But: Healthy 70-90 year olds still have neurogenesis. It’s reduced, but not absent.

What determines neurogenesis in older adults?

High neurogenesis (even at 80):

• Regular exercise throughout life
• Cognitive engagement (learning, reading, complex hobbies)
• Good cardiovascular health
• Low chronic stress

Low neurogenesis (even at 50):

• Sedentary lifestyle
• Chronic stress
• Poor sleep
• High-sugar diet
• Social isolation

The key insight: Lifestyle matters more than age.

A healthy 80-year-old can have better neurogenesis than an unhealthy 50-year-old.

Practical Protocol: Maximize Neurogenesis

The evidence-based action plan:

1. Exercise (Non-Negotiable)

Protocol:

• 4-5 days per week
• 30-60 minutes per session
• Aerobic: Running, cycling, swimming, brisk walking
• Intensity: 60-80% max heart rate (can talk, but it’s effortful)

Expected results:

• BDNF increases 200-300% after single session (returns to baseline in hours)
• Chronic elevation with consistent training (baseline BDNF rises)
• Hippocampal volume +2% in 6 months

2. Sleep Optimization

Protocol:

• 7-9 hours nightly
• Consistent schedule (same bedtime/wake time)
• Prioritize deep sleep (cool room, dark, quiet)

Why:

• Most neurogenesis occurs during deep sleep
• Sleep deprivation cuts neurogenesis in half

3. Cognitive Challenge

Protocol:

• Learn something complex (language, instrument, programming)
• 3-5 hours per week of effortful learning
• Novelty matters (new > familiar)

Why:

• New neurons integrate into learning circuits
• Cognitive challenge signals “we need more neurons here”

4. Intermittent Fasting (Optional but Effective)

Protocol:

• 16:8 fasting (16 hr fast, 8 hr eating window)
• Or: 5:2 (normal eating 5 days, reduced calories 2 days)

Why:

• Fasting increases BDNF
• Ketones (produced during fasting) enhance neurogenesis

Caution: Not for everyone (consult doctor if medical conditions).

5. Omega-3 Supplementation

Protocol:

• 1-2g EPA+DHA daily (from fish oil or algae oil)
• Or: Fatty fish 2-3x per week (salmon, mackerel, sardines)

Why:

• DHA is a structural component of neurons
• Supports neurogenesis and neuron survival

6. Stress Management

Protocol:

• Daily meditation (10-20 min)
• Nature exposure (20 min daily)
• Therapy if needed (CBT, mindfulness-based)

Why:

• Chronic stress is the #1 neurogenesis killer
• Cortisol is toxic to hippocampal stem cells

7. Social Connection

Protocol:

• Weekly deep social interaction (in-person, meaningful)
• Join communities (sports, hobbies, volunteer)

Why:

• Social connection reduces stress
• Positive interaction increases BDNF

The Takeaway

You can grow new brain cells—thousands per day—throughout your entire life.

Where it happens:

• Hippocampus (memory, learning, mood): ~700 new neurons/day per side
• Olfactory bulb (smell): Thousands/day

What controls it:

• BDNF (brain-derived neurotrophic factor) is the master regulator
• Exercise increases BDNF by 200-300% (most powerful intervention)
• Stress, poor sleep, sedentary lifestyle suppress neurogenesis

What increases neurogenesis:

1. Exercise (30-60 min, 4-5x/week) → +200-300% BDNF
2. Sleep (7-9 hr nightly) → Peak neurogenesis during deep sleep
3. Learning (complex, novel skills) → Enhances integration
4. Fasting (intermittent) → ↑ BDNF, ketones
5. Omega-3s (1-2g daily) → Neuron building blocks
6. Stress management (meditation, nature) → Protects stem cells
7. Social connection (weekly) → Reduces stress, ↑ BDNF

What decreases neurogenesis:

• Chronic stress (-50-80%)
• Sleep deprivation (-50%)
• Sedentary lifestyle
• High-sugar diet
• Alcohol (heavy use)

The implications:

• Your brain is not fixed (it’s dynamic, self-renewing)
• Aging reduces neurogenesis, but lifestyle matters more than age
• Depression linked to low neurogenesis (exercise/antidepressants boost it)
• Memory and learning depend on new neurons

The protocol is simple:

• Move your body (exercise is non-negotiable)
• Challenge your mind (learn something difficult)
• Sleep well (7-9 hours, deep sleep)
• Manage stress (meditation, nature, therapy)
• Eat omega-3s (fish or supplement)

Every day, you’re either growing new neurons or suppressing their creation.

Your brain is building or decaying.

Which will you choose?

This is part of the Brain Series. Neurogenesis proves your brain’s remarkable capacity for renewal. The question isn’t whether you can grow new neurons—it’s whether you’ll create the conditions for it to happen.