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How Smells Influence Our Hormones, Health & Behavior | Dr. Noam Sobel

Episode 122 May 1, 2023 3h 10m 19 insights
In this episode, my guest is Noam Sobel, PhD, professor of neurobiology in the department of brain sciences at the Weizmann Institute of Science. Dr. Sobel explains his lab’s research on the biological mechanisms of smell (“olfaction”) and how sensing odorants and chemicals in our environment impacts human behavior, cognition, social connections, and hormones. He explains how smell is a crucial component of “social sensing” and how we use olfaction when meeting new people to determine things about their physiology and psychology, and he explains how this impacts friendships and romantic partners. He explains how smell influences emotions, hormone levels, memories and the relationship between breathing and autonomic homeostasis. He describes how smell-based screening tests can aid disease diagnosis and explains his lab’s work on digitization of smell — which may soon allow online communication to include “sending of odors” via the internet. Dr. Sobel’s work illustrates how sensitive human olfaction is and how it drives much of our biology and behavior. For the full show notes, visit hubermanlab.com.
Actionable Insights

1. Optimize Hydration & Electrolytes

Ensure adequate hydration and electrolyte intake (sodium, magnesium, potassium) by dissolving an electrolyte mix like Element in 16-32 ounces of water first thing in the morning and during physical exercise, as proper levels are critical for optimal brain and body function and nerve cell activity.

2. Prioritize Nasal Breathing

Opt for nasal breathing over mouth breathing whenever possible, as it is beneficial for overall health and plays a significant role in shaping and modulating cognitive processing.

3. Restore Energy with NSDR/Meditation

Utilize meditation apps offering Yoga Nidra or Non-Sleep Deep Rest (NSDR) protocols, even for short 10-minute sessions, to restore cognitive and physical energy and explore different brain-body states.

4. Olfactory Training for Recovery

If experiencing smell loss, intentionally and constantly sniff a variety of common items from your home to keep olfactory neurons active, as olfaction is a ‘use it or lose it’ system and this training can aid recovery.

5. Enhance Cognition via Nasal Inhalation

During cognitive tasks, particularly those involving visual-spatial processing, prioritize nasal inhalation, as it has been shown to time and drive neural activity, leading to significantly better performance compared to exhalation.

6. Prioritize Smell in Key Choices

Recognize that in fundamental choices like food and romantic partners, smell often overrides visual appeal, acting as a primal driver of preference or aversion that strongly influences behavior.

7. Odor Similarity Predicts Friendship

Recognize that individuals who smell more similar to each other are more likely to form ‘click friendships,’ as body odor similarity can predict initial social affinity and perceptions of likability even among strangers.

8. Recognize Constant Odor Sampling

Be aware that humans constantly and often subconsciously sample their own body odor (e.g., by touching their nose after a handshake) and the odors of others, as this is a natural behavior influencing social interactions.

9. Understand Baby Odor’s Influence

Be aware that babies emit hexadecanal, a semi-volatile molecule that can chemically influence adult behavior by reducing aggression in males and increasing it in females, serving a protective function for the offspring.

10. Recognize Tears as Chemosignal

Understand that emotional tears, despite being odorless, act as a chemosignal that can significantly reduce free testosterone and lower aggression in men who sniff them, suggesting a non-verbal communication function.

11. Use Scent for Partner Connection

When a romantic partner is absent, consider smelling their articles of clothing to evoke positive connotations and comfort, as scent plays a significant role in maintaining emotional connection.

12. Leverage First Olfactory Experiences

Be mindful that the brain forms particularly robust and lasting memories from the first exposure to a smell, a phenomenon that can etch experiences into one’s being more profoundly than other sensory stimuli.

13. Regular Olfactory Health Checks

Advocate for or undergo regular olfactory testing, such as the UPSIT or Sniffing Sticks, as a non-invasive way to track changes in smell over time, which could serve as an early indicator for potential neurodegenerative diseases.

14. Observe Nasal Cycle for ANS

Be aware that your nostrils alternate airflow every 2.5 hours on average, reflecting the balance of your autonomic nervous system, which can serve as a marker for physiological states and disease.

15. Cold Exposure Shifts Nasal Balance

Be aware that exposure to cold, such as cold water hand exposure, can generate a shift in your nasal balance, indicating that autonomic arousal may drive changes in the nasal cycle.

16. Cannot Willfully Control Nasal Cycle

Do not expect to willfully shift your nasal cycle (airflow between nostrils) through thought alone, as scientific studies indicate that even experienced practitioners cannot achieve this.

17. Challenge Olfactory Subjectivity Myth

Recognize that human olfactory perception is largely shared and not highly subjective, with most people agreeing on the pleasantness of 90% of odors, and dissimilarities often stemming from a few outlier scents or a lack of common language anchors.

18. Acknowledge Shared Olfactory Preferences

When discussing smells, understand that despite a few polarizing exceptions like cilantro, humans largely agree on the pleasantness of most odors, with a high correlation across individuals.

19. Fear is Chemically Contagious

Recognize that humans emit a specific body odor when experiencing fear, which can increase autonomic arousal in others who perceive it, making fear chemically contagious.