Summary of Huberman Lab Podcast Episode: The Impact of Smells on Hormones, Health & Behavior | Dr. Noam Sobel
Podcast: Huberman Lab
7 min. read
— Description —
Discover the fascinating world of our sense of smell and how it impacts our relationships, health, and decision-making Explore the intricate connection between our olfactory system and cognition, and learn why losing our sense of smell can have profound implications Uncover the surprising ways our nose guides us in our everyday lives, from choosing what to eat to selecting a romantic partner
Dive into the potential future of digitized olfaction in medical diagnoses.
The Impact of Smells on Hormones, Health & Behavior | Dr. Noam Sobel
Table of contents
Key Takeaways
- The human sense of smell is innately extremely sensitive and can be trained to be even more sensitive, especially in the absence of other senses (like vision or hearing)
- Every time you meet someone you are taking chemicals from that person and applying it to your own body to process information about that person – this may explain why some people become “fast friends” or click right away
- If you lose your sense of smell for 1-1.5 years, it’s unlikely you’ll ever get it back; it’s a ‘use it or lose it’ system
- Loss of smell is an early indicator of neurological degeneration and disease
- We’re constantly shifting our nasal cycle AKA which nostril we use most through a mechanism driven by the sympathetic/parasympathetic nervous system
- Information processing & cognition is linked to our olfactory system
- We are always sensing our own odor clouds to change our cognition and behavior – whether you realize it or not
- In our most basic behaviors, we follow our nose not our eyes: if a food is visually appealing but smells bad, we are less likely to eat it; we’ll be more attracted to a romantic partner who smells pleasant regardless of looks versus a potential partner who looks nice but smells bad
- The future of digitized olfaction may be used in medical diagnoses (but nowhere in the near future)
Introduction
- Dr. Noam Sobel, Ph.D. (@LabWorg) is a professor of neurobiology in the department of brain sciences at the Weizmann Institute of Science. His research focuses on the biological mechanisms of smell (“olfaction”) and how sensing odorants and chemicals in our environment impacts human behavior, cognition, social connections, and hormones.
- Andrew Huberman and Dr. Noam Sobel discuss how smell is a crucial component of our social lives and interactions, the influence of smell on emotions, hormone levels, and memories, and the future of being able to send smells via the internet.
- Host: Andrew Huberman (@hubermanlab)
Major Components Of Smell
- We smell through our nose and mouth – a big part of olfaction to food and taste is through our mouth
-
Molecules travel up our nose and interact with receptors lining the nasal structure and eventually turn into a neural signal
- To emphasize its importance, a lot of our genome is actually dedicated to olfaction
- Each receptor will activate a different subset of receptors
-
A hit in the back of the head severs an essential component of smell and causes loss of smell, either partially or completely
- If you don’t get it back within 1-1.5 years, you will never get it back
- Alpha lipoic acid may recover smell, but data is mediocre at best
- “Olfaction is a definite use it or lose it system” – Dr. Noam Sobel
The Power Of Olfaction Beyond Smell
- Smell and memories are linked: first-time experience of smell develops a particularly robust memory cue
-
Humans can follow scent trails buried in the grass, especially if deprived of vision and other senses
- Humans innately have a remarkable sense of smell but you can improve and further train your ability to smell in as little as 4 days
- The human detection threshold is extremely sensitive
-
There’s a constant shift in our nasal cycle, how we use our nostrils from side to side particularly when sleeping– it’s driven by switches in the sympathetic/parasympathetic nervous system
- You can tell the difference between adults with ADHD and not, and even whether they’re medicated just by monitoring olfaction seesaw
- The nasal cycle seems to be more about brain function than actual olfaction demands
- Information processing is linked to olfactory inhalation
- Nose breathing shapes cognition: there is data supporting the idea that nasal inhalation is timing and modulating cognitive processing
-
Loss of sense of smell is a strong indicator of neurological disease and neurodegeneration – the nose is a path to our brain, loss of smell shows up in Parkinson’s and Alzheimer’s years before any other symptom
- Though there are clinical tests, the problem is olfaction hasn’t been properly digitized so it’s tough to measure and link causality
- Also, olfaction isn’t tested in newborns so it’s tough to measure olfaction deterioration without a baseline
Using Olfaction To Process Social Interactions
- People are constantly smelling themselves and others, consciously or subconsciously
- You can see this clearly in dogs, when they meet they smell each other
-
Handshaking is sort of the human version of smelling each other – we’ll often handshake then use our hands to fix our hair or touch our nose, etc.
- Studies show we even subconsciously even bring our hands to our nose and sniff after the handshake
- “Click friendships”: there are people you meet and hit it off right away – the theory is a similarity in body odor may contribute to becoming fast friends
- Olfaction and reproduction are linked in all mammals, including humans – romantic selection in humans is based on body odor
-
In pregnant female mice, a strange smell in the male’s urine can cause a miscarriage
- Humans have a very high rate of spontaneous (no known reason) miscarriage – we could possibly have some trigger related to olfaction but there is nothing clearly defined yet though there are theories of relationship to olfactory memory
- A specific scent of babies reduces aggression in the father and increases aggression (likely translated into protectiveness) in mothers
- Women and synchronized meses: there does appear to be a chemo-signaling effect but the statistics of cyclic events are tricky and it’s unlikely chemo-signaling is the whole story
Relationship Between Odors & Other Aspects Of Life
- In a way, fear is contagious: we emit a specific body odor when we’re in a state of fear, and this is picked up by others in our vicinity
-
Most of the non-verbal communication in mammals is through scent of urine (but obviously that’s replicable in humans) – instead, tears are the human chemical signal
- Tears are odorless but when sniffed, there’s a pronounced reduction in testosterone in men
- The same finding was replicated in mice
- Dogs also shed emotional tears
- Engineered meats are looking to add the smell of real meat as a way of enticing more customers
- Sense of smell is incredibly similar, in contrast to what people think – we are biased by outliers and there are some polarizing smells but in reality, people agree on 90% of odors
- Sending scents through computers: Google has a well-financed startup aiming to digitize smell
- COVID has caused a renaissance of olfaction research because people are more acutely aware of the importance of olfaction
- It is possible to predict the odor of something measuring molecules
Articles & Other Resources
-
Articles
- The Age of Olfactory Bulb Neurons in Humans (Neuron)
- The Privileged Brain Representation of First Olfactory Associations (Current Biology)
- Mechanisms of scent-tracking in humans (Nature Neuroscience)
- Measuring and Characterizing the Human Nasal Cycle (PLOS ONE)
- Human non-olfactory cognition phase-locked with inhalation (Nature Human Behaviour)
- A social chemosignaling function for human handshaking (eLife)
- There is chemistry in social chemistry (ScienceAdvances)
- MHC-dependent mate preferences in humans (Proceedings of the Royal Society B)
- An Exteroceptive Block to Pregnancy in the Mouse (Nature)
- Fear-Related Chemosignals Modulate Recognition of Fear in Ambiguous Facial Expressions (Psychological Science)
- Sniffing the human body volatile hexadecanal blocks aggression in men but triggers aggression in women (ScienceAdvances)
- Menstrual Synchrony and Suppression (Nature)
- Regulation of ovulation by human pheromones (Nature)
- Human Tears Contain a Chemosignal (Science)
- Why Only Humans Shed Emotional Tears (Human Nature)
- Revisiting the revisit: added evidence for a social chemosignal in human emotional tears (Cognition and Emotion)
- Increase of tear volume in dogs after reunion with owners is mediated by oxytocin (Current Biology)
- An olfactory self-test effectively screens for COVID-19 (Communications Medicine)
-
Other Resources
- Joachim Löw video
- Osmo
- Odor Space