Does the cure for the winter blues lie in your gut?

As the winter darkness closes in, many will already be making plans to combat seasonal affective disorder, but instead of reaching for a therapy lamp this winter, should you be upping your prebiotics? Emilie Lavinia reports

A gut feeling: 90 per cent of neurotransmitters for serotonin are found in the digestive tract (Getty)

For every person who welcomes winter as a time of cosy hibernation and comfort food, there will be another one who dreads the darker days knowing that it will bring on a bout of seasonal depression. Experts believe that 35 per cent of the UK population is affected by low mood due to the shift in seasons, but take into account those who have never visited a doctor to report mental health symptoms in winter and that percentage is probably even higher.

During the winter, our sun exposure is limited in the UK due to cloud cover and fewer daylight hours. Sun exposure and time outside are fairly crucial for mental health maintenance. A decrease in sunlight can disrupt your body’s natural circadian rhythm, confusing the neurotransmitters that work to regulate your hormone levels. Limited sun exposure in cooler, darker months also equates to less vitamin D in the body and, of course, the more time we spend indoors, the less we’re exposed to fresh air, exercise and social enrichment. This all fosters a higher likelihood of anxiety and depression.

Naturally, plenty of us look for ways to maintain and improve mental wellbeing during the winter. We might turn to seasonal affective disorder, or SAD lamps, daily exercise or better sleep to stave off poor mental health – all solutions that are proven to help with nervous system and emotional regulation.

The lack of sunlight in winter months can lead to a disruption in the body’s natural rhythm (Getty)

However, a new clinical trial suggests we should actually be taking a look at our gut microbiome and supplementing prebiotic fibre as a long-term mental health fix – especially at this time of year.

Over the years, several studies have shown that our mood is also closely linked to the health of our gut. A 2022 paper from NIH states that “the disorder of the intestinal microbial system structure plays a crucial role in depression. The gut-brain axis manifests a potential linkage between the digestion system and the central nervous system”.

Gut health expert Dr Azadeh Ovaici explains: “Mood and anxiety are directly correlated with hormones and chemical changes inside the body and an intake of prebiotics has shown to increase the levels of serotonin (the happy hormone), reduction in inflammatory cytokines markers (CRP) inside the body as well as changing the microbiome flora in the gut, which results in a reduction in catecholamine production (the fight or flight hormone) which reduces the fear response and hence anxiety.”

“We know that 90 per cent of neurotransmitters for serotonin are found in the gut, and this could explain that ‘sick to the stomach’ feeling we have when we are anxious or when we are feeling nervous we often have to run to the toilet. Also, there are a lot of studies showing that people who suffer from inflammatory bowel conditions such as ulcerative colitis have higher rates of depression and anxiety.”

Many experts, including Zoe founder Professor Tim Spector, have advocated healthy eating to support mental health, recommending an optimal microbiome as a way of staving off the symptoms of low mood, fatigue and infection. So could a diet lacking in gut-friendly nutrients, combined with a lack of sun exposure create a perfect storm and potentially be laying the foundations for year-round low mood, anxiety and severe depression?

The study at Myota used a supplement that can work for everyone, despite possible differences in microbiome composition (Getty)

The latest study on the gut-brain axis seems to say so, but it also offers up a solution. A 12-week clinical trial on the effects of prebiotic fibre on mood and inflammation has been hailed as “a breakthrough”. The study, which delivers new data based on the health of 60 participants diagnosed with metabolic syndrome (MetS), reveals that taking a microbiome-targeting prebiotic fibre blend not only “significantly reduces systemic inflammation but also improves mental health markers, such as stress, anxiety and depression”.

Participants in the treatment group took a 10g prebiotic fibre supplement daily, while the control group followed only general healthy eating advice. The results showed that after 12 weeks of taking the prebiotic supplement, participants experienced a 45 per cent improvement in mood and a 44 per cent reduction in anxiety.

These findings point to a promising, cost-effective treatment for managing metabolic and mental health challenges, with potential implications for enhancing overall longevity. However, a major stumbling block for this type of research lies in the uniqueness of our gut microbiota. Variations in gut composition have made it difficult to create and test a clinically effective supplement in a controlled trial. Experts have long been aware of the benefits of prebiotic fibre, but have spent decades researching how to manage the variables of gut microbiome and fibre fermentation.

The scientific team at Myota have been responsible for a lot of the legwork here and the new study’s outcomes come as the result of testing a patented mix of diverse prebiotic fibres. In other words, the supplement used in the trial accounts for microbiome variability and can work for everyone, regardless of microbiome composition.

By nourishing the bacteria, the prebiotics help to maintain a thriving gut microbiome, which in turn can strengthen the gut-brain connection and support digestive health, immune function and mental health

Alexa Mullane, nutritional therapist

Supplements are a huge business and it’s becoming increasingly difficult to discern which blend and brand might actually impact your body positively. The human body is naturally wired to extract nutrients from food, something it does very well. Supplements, on the other hand, present a challenge. Some are more efficient than others because they come from food-grown sources or they’re processed in a way that makes them more bioavailable. Others contain mere traces of what your body needs to thrive and others are obliterated by stomach acid before they can do any real good.

So a clinical-grade supplement and the results gleaned from the study do seem to be groundbreaking as far as connecting the dots around food and mood are concerned.

Dr Ovaici explains that “prebiotics are the food to help keep your friendly gut bacteria alive. Foods that are high in prebiotics are asparagus, Jerusalem artichoke, onions, garlic, leek, tomatoes, oats, honey, banana, peas, barley, rye, wheat and beans – a lot of us don’t eat these food groups in a high enough quantity to get the optimal effect from them”.

The study also states that the treatment group showed a “significant reduction in systemic inflammation”. Inflammation has long been associated with gut issues, including metabolic syndrome, but also (albeit less conclusively) with stress, anxiety and sleep disorders.

“There is a strong bidirectional relationship between metabolic syndrome, with anxiety disorders and major depression with population-based studies showing an increased prevalence of anxiety and depression among individuals with MetS (due to the likely increase in systemic inflammation in this population),” say the researchers of their findings, confirming the idea that depression may have a neuroinflammatory basis.

A balanced diet is a must for good gut health (Getty)

So, to lift a low mood, is it really as easy as just popping a pill every day? Notably, the improvements the study’s participants experienced were achieved without any significant lifestyle or dietary changes. However, a balanced diet, time outside and regular exercise is still a must for good health and longevity. There are several causes for stress, low mood and depression and not every single one of them originates in the gut. With that said, treating inflammation and gut issues has certainly been proven to help raise mood, thanks to the latest research into the connection between the gut and the brain.

Dr Caitlin Hall, head of research at Myota, tells The Independent: “This new study reinforces the critical role that the gut plays in mental health through the gut-brain axis. The significant reduction in both inflammation and mental health symptoms, seen alongside improvements in microbiome composition, suggests that precision prebiotic fibre could become a vital tool in promoting both physical and mental wellbeing.”

“The findings highlight that prebiotic fibres not only help reduce inflammation but may also play a crucial role in preventing the long-term effects of chronic, low-grade inflammation, often referred to as ‘inflammaging’. This type of inflammation has been linked to several age-related diseases and mood disorders (including cardiovascular disease, type 2 diabetes, depression and anxiety), further emphasising the importance of targeting inflammation for healthy longevity.”

Nutritional therapist Alexa Mullane explains that “this recent study is very exciting because it confirms the connection between bacteria and mental health, and emphasises the importance of feeding our bacteria with beneficial prebiotic fibre to allow them to flourish. By nourishing the bacteria, the prebiotics help to maintain a thriving gut microbiome, which in turn can strengthen the gut-brain connection and support digestive health, immune function and mental health”.

This study and the trial’s results support the growing body of evidence linking systemic inflammation and GI issues with mental health outcomes. So before you pass off your low mood this winter as inevitable, you might want to consider the health of your gut and what you’re putting in it.