DR MICHAEL MOSLEY on how your diet can help you beat Blue Monday

DR MICHAEL MOSLEY on how your diet can help you beat Blue Monday: Eating more foods that contain living bacteria such as onions, leeks and berries can have the potential to alter and even improve our mental health

  • Prof Dinan coined ‘psychobiotics’ to describe link between diet and emotions 
  • These are foods that contain living bacteria that can alter out mental health
  • Psychobiotic diet includes eating foods rich in fibre that feed healthy bacteria

Brace yourself for tomorrow. According to experts, the third Monday in January is the most depressing day of the year.

A combination of bad weather and the arrival of Christmas credit card bills has earned it the title of Blue Monday, as coined by British psychologist Cliff Arnall.

Personally, I take the idea of Blue Monday with a pinch of salt – it turns out that Cliff, who was apparently a part-time tutor at Cardiff University at the time, was paid to write about it as part of a travel company press release. But there’s no doubt that this time of year is gloom-inducing.

So there’s no better time to offer you science-backed tips to lift your mood.

Psychobiotics, Professor Ted Dinan says, are foods that contain living bacteria that have the potential to alter and even improve our mental health

The fascinating relationship between food and mood is a current obsession of mine – something that many GPs may not think of when advising on ways to beat the blues. Should they? New research I was involved with suggests it might be an area worth looking at.

It should be pointed out that, for those with – or who suspect they may have – depression, seasonal or otherwise, or another mental health diagnosis, then following standard medical advice is essential.

And there is no good evidence that diet alone is a cause, or treatment.

But the conclusions of my own study add to a host of emerging research that shows the strength of the connection between what we eat and how we feel. And it turns out this connection has a lot to do with the microbiome – the 2 lb to 3 lb of bacteria that live in your gut…



Take a Vitamin D supplement. Doctors recommend 10mg a day of the ‘sunshine vitamin’. Get them from the chemist.


Invest in a little box that emits bright light to regulate circadian rhythm and boost mood.


It’s a challenge to exercise outdoors when it is cold and wet but even a walk is beneficial. Just put on some wellies and take a brolly. If you really can’t face it, do squats and press-ups inside.


For the current series of the BBC2 show Trust Me, I’m A Doctor, I was keen to investigate how what we eat affects our emotions.

So, with the help of Professors Ted Dinan and John Cryan from University College Cork in Ireland, we set up a small study.

We were lucky to have these scientists on board as they are two of the world’s leading experts in this specialist field.

Prof Dinan, who is a psychiatrist, coined the word ‘psychobiotics’ to describe this link. Psychobiotics, he says, are foods that contain living bacteria that have the potential to alter and even improve our mental health. So how do microbes, which are smaller than a full stop on this page, go about affecting our brains?

Prof Dinan said: ‘The large intestine is full of trillions of microbes. They turn the food we eat into hundreds or perhaps thousands of different molecules.

‘Many of these molecules get into your bloodstream and are capable of communicating with your brain.’

Among these molecules are neurotransmitters – chemicals that influence mood and behaviour. There are also the feelgood hormones dopamine and serotonin, and chemicals such as GABA, which act in a similar way to anti-anxiety drugs.

We wanted to see if boosting levels of good bacteria in the gut, through changing diet, would make a measurable difference to mood. We recruited a number of healthy volunteers who suffered stress and anxiety and ate diets full of takeaways and sugary foods. First, the scientists conducted a series of tests on the volunteers to get a measure of their health before we made any changes. We took stool samples to analyse gut bacteria, assessed their mental wellbeing using a mood questionnaire and tested how they reacted to stress.

A psychobiotic diet involves eating foods rich in fibre that feed the healthy bacteria in our gut. This includes whole grains, onions, leeks and berries

For the stress test, they plunged their hands into a bucket of ice cold water – a painful but harmless stress trigger.

We measured the electrical conductivity of their skin, to see just how much stress they were experiencing.

Next, the volunteers were split into two groups. One group continued their regular diet, and the other followed a so-called psychobiotic diet.

This involved eating foods rich in fibre that feed the healthy bacteria in our gut. This included whole grains, onions, leeks and berries.

The group was also asked to eat naturally probiotic (healthy bacteria-containing) foods such as kefir – a fermented yogurt – and sauerkraut, a type of fermented cabbage.

They were asked to avoid takeaways for four weeks as studies suggest that some fast food contains substances that are toxic to healthy bacteria. A month later, the volunteers returned to the lab and had their stools analysed and stress levels retested. And what we found was really rather impressive.


Strikingly , there were far more healthy bugs in the guts of the volunteers eating a psychobiotic diet compared to the control group.

‘We found remarkable changes in the composition of the microbiome, even though they had been on the new regime for a short period of time,’ said Prof Cryan.

‘Four weeks on, the psychobiotic diet led to a healthier mix of bacteria in our volunteers’ gut, with an increase in good bacteria and a reduction in the bad.’

But had this change in their guts also affected their mental health?

The short answer seemed to be, yes. The volunteers who followed the psychobiotic diet did feel significantly less stressed.

When we asked them to do the ice-bucket stress test, their response fell by an average of a third. Their answers to the mood questionnaire revealed an uplift in their emotional state, too.

Our small study adds another piece to the complex jigsaw of evidence suggesting how diet can affect our gut bacteria and, in turn, our mood.

To benefit, make sure you’re eating plenty of fruit, vegetables and whole grains. Add in some fermented foods, as well as plain yogurt that contains probiotic bacteria. These simple changes might even make the winter months enjoyable. That said, I am certainly looking forward to spring.

Trust Me, I’m A Doctor is on BBC2 on Wednesday at 8pm.

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