How Probiotics Boost Immunity, Protect Your Intestinal Tract and Improve Brain Function

How Probiotics Boost Immunity, Protect Your Intestinal Tract and Improve Brain Function

Jill Davey

If you’re wondering whether you should take a probiotic, you can find lots of reasons for doing so. Probiotics can boost your energy and banish fatigue. They can help you lose weight. Even freshen your breath and improve your skin.

But for my money, three major benefits ― all essential for keeping illness and disease at bay ― clench the deal. A probiotic a day immeasurably increases your chances of keeping the doctor away.

1. Fine-Tuning Your Immune System

Your immune system is a network of cells, tissues, and organs that work in concert to protect your body against invading germs, viruses, parasites, and fungi.

As much as 80% of your immune system resides within your gut, which is home to some 100 trillion microbes (bacteria). Collectively, these tiny-but-powerful bugs constitute your microbiome, which is literally involved in every process in your body.

All bacteria are not the same. Some are ‘probiotics’. These are the beneficial bacteria ― the ‘good’ guys that guard your health. And they’re the same microscopic organisms found in probiotic supplements. Other bacteria, however, are destructive ― the ‘bad’ guys that don’t serve your interests. That are, in fact, bent on making you ill.

If you’re to be healthy, your good and bad bacteria must be maintained in the proper balance ― around 85% good and 15% bad.

Serious disruption to this balance can lead to a poorly functioning immune system that makes you vulnerable to chronic inflammation and a whole host of degenerative, age-related diseases ― diabetes, cancer, heart disease and metabolic syndrome, among others.

What can cause your microbiome to tilt toward disease? Think about your diet and lifestyle. Does your diet include junk food? Processed foods and refined sugar? Are you regularly exposed to pollution or toxic environmental chemicals that lurk in everything from plastic food containers to carpeting and upholstery?

And what about antibiotics? Too often, they’re prescribed unnecessarily, and they wipe out your microbiome ― good and bad bacteria alike. Ageing, too, can throw your bacteria out of balance.

No matter the cause of your microbial disruption, the diminutive organisms in a high-quality probiotic supplement can repopulate your good bacteria, restore proper, healthy balance to your microbiome and boost your immune system.

2. Improving Gastrointestinal Health

Probiotics do a lot to keep your gastrointestinal tract humming. For instance, they help your digestion by facilitating the breakdown of food and enable you to absorb the nutrients you consume. And, of course, they work to restrain your population of harmful bacteria so they don’t get out of hand.

That’s important, because when bad bacteria take over too much territory in your gut, poor digestion and other unpleasant symptoms such as gas, bloating, stomach irritation, and diarrhoea or constipation are almost sure to follow.

Even worse, if your microbiome remains unbalanced for a prolonged period of time, you’re at risk of developing any number of chronic health conditions ― leaky gut, for instance. Or IBD (inflammatory bowel disease) or IBS (irritable bowel disease). Diabetes, obesity and celiac disease have also been associated with an out-of-balance microbiome.

A 2015 study demonstrated that probiotics can be used both to prevent and to treat gastrointestinal conditions. Other clinical studies show that probiotics are specifically beneficial for treating IBS, and, by reducing chronic inflammation and achieving immune stability in the gut, they improve IBD, a condition associated with ulcerative colitis (UC) and Crohn’s disease.

Leaky gut occurs when the intestinal lining ― which is supposed to be your immune system’s first line of defence ― develops pores, or holes, that allow undigested food, toxins, yeast, assorted pathogens and waste to pass into the bloodstream and be transported throughout the body.

Leaky gut may be caused by:
A diet high in refined sugars, processed foods, preservatives and refined flours ― all of which your body regards as toxic
Stress, which batters the immune system
Persistent inflammation, which is linked to almost all disease

Probiotics, which can strengthen the intestine’s protective barrier, are an effective way of preventing or treating leaky gut.

3. Bolstering Your Brain (Via Your Gut)

It’s interesting that such phrases as ‘gut instinct’, ‘gut feelings’ and ‘gut reaction’ entered our vocabulary many years before anyone was talking about the gut-brain axis. Maybe we somehow intuitively sensed a connection between the brain and the gut long before science discovered it and gave it a name.

Neurons are generally thought of as brain cells, but did you know that between 200 and 600 million neurons are found tucked neatly into folds of the tissue that lines your gastrointestinal tract?

It’s true that those neurons aren’t really involved in what we generally consider thought, but that doesn’t mean they’re passive. In fact, your gut, with all those neurons, plays a crucial role in things we normally associate with the mind ― cognitive processes like memory, learning and decision-making, as well as stress, anxiety and feelings of sadness.

Neurons that act as neurotransmitters such as serotonin are also found at both ends of the gut-brain axis. In the brain, serotonin is particularly known for regulating mood. However, 90% of the serotonin found in the body is produced in the gut, where, aside from helping to move waste through the intestinal tract, it also impacts brain function.

The fact that the concentration of serotonin is greatest in the intestine may explain why treating depression with antidepressants, which raise serotonin levels in the brain, often don’t work whereas dietary changes do.

No wonder the gut has come to be dubbed ‘the second brain’!

Science has long recognized that depression and other negative feelings are linked in some way to turbulence in the southern regions of the body ― diarrhoea, constipation, bloating, pain and IBS, for example. However, over the past several years, research has vastly increased our understanding of the complex, reciprocal interactions between gut and brain ― how each affects the other.

The term ‘gut-brain axis’ refers to the two-way communication that primarily moves along the vagus nerve, which spans the distance between the central and enteric nervous systems. The central nervous system encompasses the brain and spinal cord, and the enteric nervous system comprises the nerves that control the intestinal tract.

Put another way, the emotional and cognitive parts of the brain are directly connected with the intestinal functions of the gut. Each influences the other. If the gut isn’t properly functioning, then the brain is involved, and vice versa.

One UCLA study researcher wrote:
Researchers have known that the brain sends signals to your gut, which is why stress and other emotions can contribute to gastrointestinal symptoms. This study shows what has been suspected but until now had been proved only in animal studies: that signals travel the opposite way as well.

“Time and time again, we hear from patients that they never felt depressed or anxious until they started experiencing problems with their gut,” [Dr. Kirsten] Tillisch said. “Our study shows that the gut-brain connection is a two-way street.”

Most of us know the gut’s importance for physical health, but its influence is equally critical for mental health. Bad bacteria in the gut can cause neurochemical changes in the brain, mood disorders and profound changes in behaviour and personality.

Your microbiome affects the bidirectional communications that pass between your gut and your central nervous system. On the lower end, these exchanges may result in intestinal disruptions; on the upper end, the result might be increased stress, depression, anxiety or impaired cognitive functioning.

Many of these effects appear to be linked to specific strains of bacteria. This finding suggests that probiotics may play an important role in restoring a healthy microbial habitat and relieving some neurologic disorders.

The Last Word . . .

Year by year we’re learning ever more about the benefits of probiotic supplementation. Already, however, we have conclusive evidence that a well-balanced microbiome is essential for defence against disease, good intestinal health and optimal mental functioning.

Take good care of your good bacteria, and they’ll take good care of you!


Carabotti, M., Scirocco, A., Maselli, M.A., Severi, C. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of Gastroenterology. 2015 Apr-Jun; 28(2): 203-209.

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