The Truth About Oxytocin AKA The Love Hormone

Oxytocin, the so-called 'love hormone', could actually play an important role in combating stress-related digestive problems. That’s according to recent research conducted at Penn State University College of Medicine, which looked at the links between stress and gastrointestinal issues.

So what does this actually mean? Could a really great, oxytocin-releasing cuddle be the solution to your stress-IBS woes? Sadly, no, it’s not quite that simple.

According to the research, stress "disrupts gastrointestinal functions and causes a delay in gastric emptying (how quickly food leaves the stomach)," leading to symptoms such as bloating, discomfort, nausea and diarrhoea.

The study – which was carried out on male rats – used new techniques to manipulate oxytocin circuits via injections into the rats’ brains. Researchers then analysed the effects of the hormone on how the stomach responds to stress.

Researchers concluded that "activation of these oxytocin circuits reversed the delay in gastric emptying that occurs normally in response to stress, by increasing muscle contractions of the stomach, while inhibition of these neurocircuits prevented adaptation to stress."

In other words, having more oxytocin reversed stress-related stomach issues (in male rats), stimulating muscle contractions to help the stomach empty more normally. Meanwhile, having less oxytocin meant the rats’ stomachs weren’t able to adapt to stress.

Commenting on their findings, researcher R. Alberto Travagli said that this could prove particularly useful when it comes to tackling gastrointestinal disorders in women. "Women are more vulnerable to stress and stress-related pathologies, such as anxiety and depression, and report a higher prevalence in gastrointestinal disorders," he explained.

"Our previous studies showed that vagal neural circuits are organised differently in males versus females," he added – although, interestingly, the new research doesn’t mention either women or female rats.

The next step, according to Dr Travagli, will be a series of studies designed to help "develop targeted therapies to provide relief for women with gastrointestinal disorders."

While this could be really promising for those afflicted by stress-related tummy troubles, endocrinologist Dr Helen Simpson advises caution about extrapolating too much from these early animal studies. "Humans are a bit more complex than rats, so you can’t always reproduce the same results," she explains.

"There is a bit of a danger of adding two and two and getting five. This study involves direct injections into rat brains, which is not very physiological. I’d be very cautious about over-interpreting it to humans, or to differences between men and women," Dr Simpson adds.

The big question, she says, is whether the results indicate association or causation. "It’s very difficult to say, and the same is true of studies where people have looked at the role of oxytocin in depression. It’s hard to say whether it’s association or causation because there are so many factors involved."

So what do we know about the 'love hormone'? Oxytocin is a hormone produced in the hypothalamus region at the base of the brain and secreted by the pituitary gland. It is popularly associated with love, cuddling, monogamy and social attachment – but it has also been linked to stress relief, relaxation, positive memories and empathy. Other research suggests it can actually have less positive effects, like promoting prejudice and discrimination.

It’s fair to say the messages are mixed. Crucially though, much of what we think we know about oxytocin is primarily based on animal studies, like the Penn State one. When it comes to hard evidence on how it works in humans, oxytocin’s main roles are much more functional: assisting in sperm production, conception, childbirth and breastfeeding.

"Animal data suggests oxytocin is involved with attraction and attachment but there isn’t so much hard data about that in humans. What we do know is that it’s very much involved in human lactation and childbirth," Dr Simpson explains.

"Oxytocin is produced when the baby suckles, which helps the milk move into the breast and be released. It’s also involved in childbirth, stimulating contractions of the uterus and increasing production of prostaglandins, which further increase and intensify those contractions. If someone needs to have their labour induced, manufactured oxytocin is given through a drip to induce labour, or to strengthen the contractions," she adds.

Oxytocin is controlled by a 'positive feedback' loop, where the hormone being released stimulates the brain to release more of it. In breastfeeding, for example, this means that when a baby suckles at its mother’s breast, the stimulation leads to oxytocin secretion, which in turn causes milk to be let down into the breast while also signalling for the brain to produce more oxytocin. This cycle continues to sustain itself until the baby has finished feeding.

The same is true in childbirth, where the positive feedback of oxytocin being released helps to increase the intensity and frequency of contractions until the baby has been born.

There’s also evidence that oxytocin is involved in conception. In men, it appears to play a role in sperm movement and the production of testosterone by the testes. Meanwhile, in women, it’s thought that the release of oxytocin could trigger the muscular contractions of orgasm, which help to move sperm up the reproductive tract. The female orgasm could therefore play an important role if you’re trying to conceive, with oxytocin stimulating the vaginal muscles to give sperm a helping hand on its journey towards the egg.

Dr Simpson says that there is some evidence that oxytocin also plays a role in social behaviour – but the evidence for this is currently stronger in animals than it is in humans. According to the Society for Endocrinology, oxytocin has "been shown to be important in human behaviours, including sexual arousal, recognition, trust, anxiety and mother-infant bonding." Research is also being carried out to look at the role of oxytocin in addiction, brain injury, anorexia, stress and depression, among other topics.

However, one of the major things that’s not yet fully understood is what happens if humans have too much or too little oxytocin. High levels of oxytocin have been linked to a prostate problem known as benign prostatic hyperplasia, which can make it difficult to pass urine. Meanwhile, a lack of oxytocin in nursing mothers can prevent the milk let-down reflex and make breastfeeding difficult.

Beyond these though, Dr Simpson says, "there’s no strong data to say that people are particularly affected by not having enough oxytocin. There’s no clear syndrome that we’d call 'oxytocin deficiency'."

Although low levels of the hormone have been linked to depression, autism and autistic spectrum disorders, there’s not currently enough evidence to support manipulating oxytocin levels as a treatment for any of these conditions.

Back to our guts – could oxytocin play a role in settling our stomachs under stress? We know that oxytocin’s key roles in humans involve muscle contractions (in the uterus and possibly the vagina) and moving things (milk, sperm, babies) to where they need to be. It is therefore possible that increasing oxytocin could also stimulate stomach contractions and help food to move more easily out of the stomach. So in theory, sure. Much of what we know about oxytocin in animals does appear to ring at least slightly true in humans – albeit with lots more complex factors involved.

What’s for sure is this: our fascination with oxytocin and what it does to our bodies and brains is never-ending. We want it to explain why and with whom we fall in love. We want it to cure our ills. We want it to help us understand ourselves. Science still has some way to go before it can definitively answer any of our questions.