How Smell, Taste & Pheromone-Like Chemicals Control You

Our whole nervous system is designed to move us toward or away from things
Smell, taste, and ability to sense the chemical state of others has a profound influence on who we spend time with
Innate odor responses signal a call to action and elicit alertness in the brain – we know to go away from smoke or fire and towards fresh baked cookies
Smell is closely tied to memory
You can train yourself to have a better sense of smell by sniffing deeply through your nose 10-15 times, then smelling something with a strong scent (such as an orange or mint)
Olfactory dysfunction is common in traumatic brain injuries and can be a sign of progress in recovery
It’s possible we have a 6th taste receptor to detect fat in addition to the 5 traditional taste receptors we know (sweet, sour, bitter, umami/savory, salty)
The specifics of human pheromone chemicals are unknown but it is clear that some form of chemical-chemical signaling between humans exists

Smell starts with sniffing
Mucosal lining in the nose is intended to trap things
Neurons extend into the mucus and respond to different odors and compounds
Three paths: (1) innate odor responses; (2) learned responses; (3) accessory olfactory pathway
Innate odor responses call to action and elicit alertness – such as fire and smoke which cause you to move away from something – or the smell of cookies which might draw you toward something
Smelling salts trigger arousal system in brain through innate odor response pathway
Smell is closely tied to memories: we have learned associations with odors which evoke a memory or a place, thing, context
The accessory olfactory pathway is responsible for true pheromone effects in other animals
Everyone’s sense of smell is not the same: variants in genes encode for olfactory receptors – this is why some people don’t like cilantro or can smell asparagus in urine after a meal

Breathing can take place through the nose or mouth but there are documented positive effects of nasal breathing
Breathing in through your nose and sniffing has positive effects on the way you acquire and remember information
As we inhale, arousal and alertness in the brain increase
Inhaling is a cue to the rest of the brain to pay attention
Sniffing is a powerful modulator of cognition and the ability to learn
Sniffing and inhaling has an effect on being alert, paying attention, level of arousal in the brain
Takeaway: focus on nasal breathing while doing any focused activity
You can train smell to get better: practice sniffing (the act of sniffing with nothing)deeply through nose 10-15 times then sniff something with a strong scent (such as an orange)
Minty scents can increase arousal and alertness in the same way a cold shower, ice bath, or surprise will evoke

How well smell and taste is a strong indicator of our brain health
Neurons turnover through the lifespan: olfactory neurons die every 3-4 weeks and are reborn
Olfactory neuron neurogenesis is stimulated by exercise
Olfactory dysfunction is common in traumatic brain injuries
Recovery from a concussion is gauged, in part, by assessing sense of smell
Enhancing a sense of smell can create new neurons to assist recovery

We are capable of smelling and sniffing in sleep but the ability to wakeup in response to odors is reduced in REM sleep
Ability to sniff is one-way doctors assess whether someone in coma or brain dead will be able to recover

The taste system was designed to move us toward things that are good for us and move us away from things that are bad for us
We can detect 5 different tastes: (1) sweet; (2) salty; (3) bitter; (4) sour; (5) umami/savory
Each taste has a specific utility and receptor which responds to something different
Myth: different parts of the tongue house different taste receptors
Tastes that are stronger or milder represent the density of overall receptors but not location or distribution of receptors
You can distinguish taste within 100 milliseconds of touching to tongue
Five receptors encode for different things to make sure we bring in what we need and exclude what we don’t:
Sweet sense for presence of sugar
Salty receptors sense for electrolytes in a food or drink
Bitter receptors make sure we don’t ingest things that are poisonous – if we taste something bitter it will trigger the gag reflex
Sour receptors detect the presence of spoiled or harmful fermented food
Umami/savory receptor looks for the presence of amino acids necessary for brain

Possible 6th receptor: there is data to support we have receptors on our tongue which sense fat
Taste receptors are not just expressed on the tongue – they extend into the gut, digestive system, respiratory system, and on the ovaries and testes (which may speak to the sensual experience of food)

Mouth is the front of our digestive tract – it makes sense to detect so much with our nose and mouth
We have neurons within the mucosal lining of the gut that sense fatty acids, sugars, and amino acids
Dents and indentations on the tongue allow for more surface area and receptors to sense sweet, salty, bitter, sour, and maybe fat
Experience on the tongue drives different pathways in the brain
You can lose taste receptors in the mouth by ingesting something that is too hot (temperature hot) but it will come back
Ability to taste is highly subjective to training by paying attention to what you are trying to taste
How food tastes to you is different than how it tastes to other people
Carnivorous animals have no ability to detect sweet, but the concentration of savory receptors is 5000x what humans detect
Panda bears have no umami receptors but have a higher propensity for sweet receptors
People who eat a pure carnivore diet will develop more sensitive pallet and craving for savory/umami food
People who eat more plant-based diet develop heightened sensitivity for sugars and plant-based foods

Maillard reaction gives caramelization and browning to food
Maillard reaction makes amino acids are more available for detection by neurons
The relationship between smell and taste is close
A combination of texture, smell, taste combine to activate the brain and trigger desire
Processed foods make you desire more (even if they don’t taste great) because they activate neurons which triggers dopamine and make you reach for more

We make chemicals through the body through breath, tears, or possibly pheromones though pheromones in humans is a controversial topic
Chemicals made by other humans are modulating our state but not necessarily in the classic pheromone way described in animals
Example: chemicals in tears change or evoke a biological response in other humans

There is evidence both for and against the synchronization of menstrual cycles in women
People can identify t-shirt of mate with remarkable distinction
Women are better at detecting odors than men
Much of our biology is wired towards whether we should move toward food, smells, and people
Just because we haven’t identified what is acting as a pheromone, doesn’t mean chemical-chemical signaling between humans doesn’t exist

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