Probiotics: How your gut protects your mental health

You know that sinking feeling you get in ‘the pit of your stomach’? After all, who hasn’t gone through a ‘gut-wrenching experience’?

There’s a reason why these sayings are used so widely and resonate so much with people going through difficult times. Whether it’s intuition… fear… worry, trepidation, guilt, or trauma… we ‘feel’ it in our guts, both literally and figuratively.

I say literally, because exciting new research has been mounting showing the extent to which those common phrases are true.

A number of recent studies have supported the idea that the digestive tract, and particularly the billions of bacteria that line the digestive tract, play a critical role in our emotional health as well as our digestive health.

And so, if your gut is like your ‘second brain’, your mental health has as much to do with your gut health as what’s going on in your head.

But by feeding your gut the right balance of beneficial bacteria – and the stuff that those bugs feed on – you can swing your mood in the right direction and cope with life’s anxieties and stresses with ease!

Where your gut gets its instincts

In a study out of Canada, researchers gave some anxious mice antibiotics to wipe out the bacteria of their digestive tract, which created, as they say, a ‘clean slate’. (And if there’s anything that can make a mouse nervous, it’s being in one of those laboratories.)

Immediately following, the mice became less anxious and less cautious – without ANY change in their outside environments.1

But what happened next was particularly fascinating: They also saw an increase in their levels of a protein that’s been associated with more calmness and less anxiety in the brain, called ‘brain-derived neurotrophic factor’ (or BDNF, for short).

And thus, the researchers were able to manipulate the demeanour of the mice, depending on what kind of bacteria was in their gut.

For instance, when they colonized the guts of naturally passive mice with bacteria from mice that were more daring, the mice that were colonized immediately became braver and more active!

Likewise, when they took mice that were naturally more active and colonized their guts with bacteria from passive mice, the colonized mice became more passive.

Bacteria is brain food!

In another study, scientists in Ireland fed their lab mice bacteria-free food and put them through a number of tests to distress them.

They then selected one group of mice to be fed with a strain of Lactobacillus rhamnosus, similar to what you might find in many yoghurts in the supermarket dairy isle.

The bacteria-fed mice were much less anxious, ventured much farther into open spaces, and did not give up as easily in tests, compared to the control group that wasn’t given any bacteria.2

What was doubly interesting about this study was that when looking at the brain chemistry of the mice, the researchers found that the bacteria-fed mice had half the amount of stress hormones than the control mice. They also showed a chemical change in their brains that allowed for a greater presence of the neurotransmitter GABA, which is known to relax the brain.

And in yet ANOTHER mouse study, two strains of the intestinal bacteria Bifidobacterium were actually more effective in calming anxious mice than the antidepressant drug, escitalopram (Lexapro)!3

Have you never been mellow?

So now that we know that bacteria make mice less anxious, what about humans?

In 2013, a UCLA study looked at this, dividing 36 healthy women (with no known problems in their heads or their guts) into three groups:

1. one eating a mixed probiotic yoghurt,
2. one eating a dairy product that did not contain bacteria (but looked and tasted the same as yoghurt), and
3. one without any dairy products.

Researchers showed the women pictures of faces that were angry or frightened and looked at how their brains responded, using functional MRIs both before and after.

Now, normally, you’d expect an increase in activity in certain areas of the brain that are devoted to emotions. Specifically, people who are naturally anxious react highly to this type of stimulus.

But the women who ate the probiotic yoghurt had a more ‘mellow’ response, showing the intricate relationship between intestinal bacteria and the tendency for anxiety.4

But bacteria in the gut (specifically, the intestines) doesn’t really tell the whole story. As I’m fond of saying to patients, putting acidophilus and other bacteria in the intestines without preparing them first is like throwing seeds onto a parched earth.

That is, you’ve got to feed the lining of the gut, so that the ‘good’ bacteria that find its way into the area can colonize there easily.

And those substances that feed the lining of the intestinal tract are collectively known as prebiotics.

Cultivate a gut where good bugs can flourish

Prebiotics, technically, are dietary fibres and oligosaccharides (a type of carbohydrate) that feed the good bacteria in the intestine, allowing them to multiply and be healthy.

The more prebiotics available, the more good bacteria you’ll find. And so, it makes sense that prebiotics would also be important in regulating emotions… including anxiety.

In a recent study, 45 healthy adults were giving either prebiotics or a placebo daily for three weeks. The prebiotic group showed less anxiety when exposed to negative stimuli, behaving similarly to subjects who’d been given anti- anxiety medications.5

In addition, those in the prebiotics group had decreases in the levels of the stress hormone cortisol in their blood, a finding similar to the stressed mice in the earlier study. Although that’s the only human study of anxiety and prebiotics so far, those anxious rodents, of course, have been studied several times to elucidate the relationship between the two.

In one study, researchers fed mice either regular food or food augmented by two milk-derived prebiotics, 3’sialyllactose and 6’sialyllactose, before exposing them to external stresses. The effects of prebiotics were powerful on the mice, who scored better on tests looking at anxiety-related behaviour, biochemical changes in the lining of the gut (including the type of intestinal bacteria), and resilience, compared to the control group.6

And in a study from earlier this year, rats were exposed to a stressor that was the human equivalent of a car accident or death of a loved one – and the ones that had been given prebiotics recovered healthy sleep patterns sooner than the control group.7

Stress-eater? Reach for THIS

More and more, science is catching up with the simplest of natural health principles, like ‘You are what you eat’. And in laboratories across the world, the notion of the ‘gut-brain axis’ – which was once just a theory – is now being validated in real, living beings.

Perhaps soon, people will be taking ‘yoghurt breaks’ as a way of destressing during the workday! In the meantime, it’s a good idea to take a daily probiotic supplement – ideally one with billions of CFUs and multiple strains of bacteria, from a maker you trust.

Prebiotics are also available in supplement form, which is an easy way to make sure you’re getting enough of them. But prebiotic-rich foods like dandelion greens, garlic, leeks, and onions are also a delicious addition to mealtime.

Wishing you the best of health,

Dr. Glenn S. Rothfeld
Nutrition & Healing

Full references and citations for this article are available in the downloadable PDF version of the monthly Nutrition and Healing issue in which this article appears.

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