A recent article peaked my attention when discussion went into touch, attachment and the evolutionary history of oxytocin. Oxytocin or its analogues was to have initially evolved in fish to regulate water, it was a signal preventing excess water from flowing into the cells of fish. Recent studies also show it plays significant roles in fish social and reproductive behavior. When animals moved onto land oxytocin switched roles and became a signal to keep water in bodies. It is for us an antidiuretic. In mammals it’s associated with mother infant bonding and nursing, and in human’s we mostly think of it in terms of its role in smooth muscle contractions for labor and orgasm, as well as post orgasmic relaxation and connection. More recently studies have associated it with interpersonal trust in broader social relationships.
Oxytocin is one of the few hormones integral to a return to growth and repair of critical tissues compromised during stress and stress response. Simply looking at all the purposes of the molecule can be overwhelming and even confusing. The idea of one molecule and one well defined function is clearly out of the question for oxytocin. This molecule is performing a number of functions which seem aligned with toggling the investment landscape for life: more oxytocin relates to longer expected safe investment timeframes for both the body and the body's offspring, and nature seems relatively ruthless when it adapts in its absence.
The molecule turns out to be a vector for symbiote manipulation. Milk and milk products will facilitate increases in oxytocin thanks to Limos-lactobacillus Reuteri bacteria which produce oxytocin in their hosts. The increase in oxytocin from this species is shown to increase wound healing rates, but it does this only so long as the vagal nerve pathway is still intact. Administration of oxytocin from a bottle or syringe has the same effect and we can imagine a similar effect from oxytocin being induced by touch related activities.
As well, oxytocin has sex dimorphic properties. While it almost always causes relaxation in both sexes, it can sometimes cause an increase in anxiety in women. That anxiety is most likely related to a need for increased protective aggression during nursing and childcare. Despite the association with positive mood and bonding, it seems to increase the salience of all emotional signals including negative emotions in both sexes. Epigenetically, females are much more affected by the presence or absence of stimulation from their mothers in regards to oxytocin release and receptors in the amygdala. The amygdala is significantly associated with threat response. This would be a way nature signals and responds to differential investment from parents, for female offspring. Low maternal investment is likely to be due to an environment of increased stress where heightened threat detection would be adaptive.
Oxytocin is a central regulator of metabolism and implicated in reducing the rate of aging. It has been shown to extend telomeres or prevent shortening of telomeres. This likely means that increased touch and physical intimacy, dairy with L. Reuteri, and exogenous oxytocin will push out the aging countdown. It is one of a few molecules of the endocrine system that allow for an increase of energy expenditure, a decrease in appetite, and both of these with an opposition to stress. Without surprise, low Oxytocin is also implicated in obesity:
“weight loss induced by chronic oxytocin treatment is related not only to its anorexigenic effects, but also to the resulting increase in energy expenditure and lipolysis...we synthesize data related to the association between endogenous oxytocin levels, weight status, metabolic syndrome, and bone health...acute oxytocin administration reduces food intake, attenuates fMRI activation of food motivation brain areas, and increases activation of self-control brain regions.”
Beyond obesity and diabetes it’s being used or investigated to treat many conditions including: some cancers, heart disease, osteoporosis, autism, anxiety, depression, addiction, inflammation and reproductive problems. Perhaps these effects are simply by opposing cortisol and other glucocorticoids, but likely it is only one of many mechanisms given the many tissues it interacts with. Oxytocin looks like a systemic rejuvenator given the breath and centrality of the systems it helps regulate.
Oxytocin increases or at least recovers core temperature and increases peripheral metabolism and insulin sensitivity which corresponds to lower blood pressure and vasodilation of the skin, endocrine tissues, intestines, erogenous zones, and some parts of the brain. These metabolic and vasodilatory effects are likely what cause or allow much of the rapid healing, and relate to how oxytocin causes such broad effects. I expect substances with similar actions towards vasodilation and peripheral metabolism will have similar effects. As an interesting addition to autism oxytocin treatment, supplemental nicotinamide riboside (NR) used to increase cellular energy throughput, ostensibly reversing cellular age, has been shown to help treat autism through increases in endogenous oxytocin. This demonstrates that increased systemic cellular energy engenders increased oxytocin production. Causality works both directions between metabolic rate and oxytocin.
All of the noted positive effects were from endogenous or exogenous doses at a physiologically appropriate level. Extreme excess of oxytocin can cause hypotension and water intoxication in the context of electrolyte free intravenous venous infusion. The exogenous oxytocin bolus used to assist childbirth has been implicated in suckling and lactation problems. Of course, mothers only get the one dose during labor and not a supply. It would be interesting to note what pre-birth or even pre-pregnancy stress status of the mothers who did not latch properly would be. I suspect increased stress and associated oxytocin reduction would delay or reduce contraction strength as well as reduced maternal nurturing physiology. I would like to see studies sending mothers home with healthy amounts of supplemental oxytocin (and progesterone) in effect reducing the effects of maternal stress and facilitating increased maternal investment.
In the context of aging and oxytocin, it occurs to me that we had roughly two schools of thought with diverging pathways for delaying aging. One school I might call ‘the ascetic school’ and the other school ‘the hedonic school’. The ascetic school emphasizes pathways and behaviors related to water and food stress which also typically reduce reproductive function temporarily while the hedonic school aims to return signals of youth to the cells without concern or while avoiding significant deprivation or abstinence. Perhaps we need both, but I’m skeptical about adding asceticism to lives with too many chronic stressors and little time given to rest and recovery. Accordingly, I have oxytocin high on my list of aging interventions. I take it relatively frequently, as well as pursue other interventions and modalities that increase it endogenously.
Oxytocin fits well in the collection of substances and activities that reduce chronic stress by increasing peripheral temperature, lowering blood pressure, improving metabolism, and facilitating emotional awareness. Oxytocin is a molecule telling individuals to de-stress, repair their own tissues, and care for their partners and their offspring. Oxytocin is one of the ways that nature keeps us around when we are proving our reproductive and social value. May we all be fortunate enough to find and hold onto abundant amounts of oxytocin from whatever sources suit us best.
1. This begs further questions about the role of milk in the last 10,000 or more years. Milk was already a great value to cattle cultures in terms of calories (5x more than beef) and group cohesion is very important for human survival and flourishing.
Resources:
Oxytocin is a Cardiovascular Hormone
https://www.scielo.br/j/bjmbr/a/VSLC3ZfLNSGTpPFLKhgBGsp/?lang=en
https://pubmed.ncbi.nlm.nih.gov/19761809/
Research Compilation pdf
https://changlab.yale.edu/sites/default/files/files/OT_Brain_Res_all.pdf
Brain Oxytocin
https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2826.2008.01726.x
Oxytocin the Great Facilitator of Life
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2689929/
Oxytocin and Wound Healing & Bacteria
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0078898#pone.0078898-Ho1
https://pubmed.ncbi.nlm.nih.gov/26520666/
Oxytocin and metabolism:
https://pubmed.ncbi.nlm.nih.gov/23028821/
https://pubmed.ncbi.nlm.nih.gov/34203705/
https://pubmed.ncbi.nlm.nih.gov/34299356/
Male Reproduction
https://www.frontiersin.org/articles/10.3389/fendo.2020.565731/full
https://pubmed.ncbi.nlm.nih.gov/29363158/
NR, Oxytocin, and Autism
https://www.nature.com/articles/s41598-019-57236-7
Oxytocin treatment prevents the negative consequences of social isolation.
https://www.sciencedirect.com/science/article/pii/S0306453018309089