Gut Feeling | All About Serotonin

One of the prevailing myths about depression is that it is simply caused by an imbalance in the brain, often through a depletion of serotonin, a neurotransmitter nicknamed the ‘happy chemical’ (and whose scientific name is 5-hydroxytryptamine, or 5-HT). However, more recent research suggests that depression can be accelerated by everything from genetic makeup to issues with the wiring of the grey matter to stressful life events—the latter so pertinent in these unprecedented of times.


A study by the universities of Sheffield and Ulster found depression rates to have increased following the UK’s coronavirus lockdown and that those living alone in the city, aged under 35, were most likely to feel the most stress. While we’re all rightly being encouraged to keep in contact and exercise plenty, what we consume may also make a world of difference to our mental wellbeing; as tempting as it is to reach for the comfort food during times of crisis, it’s likely not beneficial in the long run, either for our brains or for our waistlines.


There is dispute about whether it is lack of serotonin that encourages depression, or if it is depression itself that causes serotonin levels to plunge. Either way, depression is regularly treated with drugs that boost serotonin levels, known as selective serotonin reuptake inhibitors, or SSRIs. SSRIs are not ‘serotonin pills’, rather prevent the serotonin, a chemical messenger that sends signals all over our bodies, from being cleared. This allows it to have a gradually greater, positive influence upon our brain and mood. (Though intriguingly, some studies have shown placebos to be up to 80 percent as effective as antidepressants such as SSRIs in treating low mood.)


Food For Thought

Mood levels may be boosted with the intake of tryptophan, an amino acid essential for the creation of serotonin. Research shows older people to perform better in cognitive tests following the consumption of tryptophan which can better memory, reduce anxiety and improve the quality of sleep. High protein foods such as turkey, eggs, cheese and salmon are all rich in tryptophans, while vegan options include soy products.


A paper published by the Journal of Psychiatry and Neuroscience found that serotonin levels can also be bolstered by exposure to sunshine or light therapy, regular exercise and meditation.


Two Brains

Serotonin regulates not only emotion, but the likes of sleep, memory and arousal, as well as appetite and digestion. So, it shouldn’t (but probably will) be of great surprise to learn that around 90 percent of it is produced in our gut, or that people suffering from depression also often report gastrointestinal issues, too. No wonder the gut is considered the body’s ‘second brain’, home to as many neurotransmitters while harbouring more neurons than the spinal cord.


All sorts of alchemy occurs in and around our bellies—the enteric nervous system—where millions of neurons interact with trillions of bacteria that adds as much as a couple of kilograms to our bathroom scales. Our ‘gut brain’ is linked to our regular brain via the vagus nerve, the longest of the cranial nerves, that also plays a pivotal role in making memories, initiating relaxation, and regulating our breathing and heart rates. A fascinating study by the Children’s Hospital of Philadelphia even found that transplanting the gut bacteria from a depressed mouse to a healthy one resulted in it too exhibiting signs of depression.


So, feeding those gut bacteria isn’t just good for our physical state, but necessary for mental health, too.

A Serotonin Aside

  • A lesser known function of serotonin is its contribution to the formation of blood clots. It is released by platelets when there is a wound to help narrow blood vessels, restricting flow and allowing clots to take shape.
  • The evidence isn’t quite yet cut and dry, but some scientists argue serotonin may be beneficial in the treatment of osteoporosis. However, confusingly, other research has shown increasing serotonin in older folk may actually reduce their bone density.
  • SSRIs may play a vital role in fighting depression, but paradoxically may also lead to sexual dysfunction in some—another cause of depression.
  • Signs of low serotonin levels may include poor memory, low moods, sweet or starchy food cravings, poor sleep, anxiety or aggression.

Don’t Get Down During Lockdown

  • Binge-watching Netflix is far more tempting than busting out the dumbbells but swap the chips and cookies for healthier alternatives like dark chocolate, nuts, Greek yoghurt and berries, and carrot sticks with humus.
  • From Les Mills to YouTube, there are heaps of online platforms offering everything from HIIT to yoga classes, consider learning to meditate, too.
  • Don’t get stuck in a rut, fresh air and sunshine is vital for mental and physical wellbeing, take regular walks around the block, read a few chapters each day in the garden.
  • Stay informed, but don’t obsess—take regular breaks from the news.
  • If you’re lucky enough to be isolating with friends, a partner or family, play games, do puzzles, hone those massaging skills!
  • Missing the occasional post-office drinks with workmates? Share a few beers or vinos with them using Skype, WhatsApp or Zoom.
  • Don’t be afraid to reach out for help if you are struggling in any way, call friends and family regularly. The New Zealand Ministry of Health has heaps of advice on website (health.govt.nz) including freephone numbers like the Samaritans (0800 726 666), Youthline (0800 376 633) and The Depression Healthline (0800 111 757). Remember, ‘he waka eke noa’ – we’re all in this together.