Our bodies and bellies are crawling with billions of bacteria, but that is probably exactly as it should be.

While we have long thought of bacteria as “bad,” it’s now becoming clear that the human microbiome -- that network of “friendly,” probiotic bacteria that live on and in our bodies -- helps keep us healthy by balancing out the "bad" bugs.

Research into probiotics has exploded in recent years, and so has the number of new products claiming to contain these friendly, bacterial warriors. So far, though, the research on probiotics is still in its infancy. There are probably hundreds if not thousands of beneficial bacteria strains and scientists are really only getting to know them and learning what they can do.

In fact, one group of experts that advises physicians, the Yale Workshop on Probiotic Recommendations, says there is only enough evidence to recommend probiotics in certain conditions, including diarrhea in adults and children; irritable bowel syndrome, and eczema linked to milk allergies.

There are still many more questions that need answers. How precisely do probiotics maintain health? Which strain of bacteria is best for what? How many probiotics do we need and for long? And are there side effects to deliberately adding all those bacteria to our bodies?

Clearly, researchers have a long way to go, But here are four areas where researchers are hopeful that probiotics may prove helpful.


The same bacteria colonies that affect our digestive health could also be influencing our mental health, some intriguing new research has found. Several studies have shown that changing gut bacteria can change stress and behaviour as well.

One recent study found that germ-free mice that are normally withdrawn can suddenly become more adventurous after receiving transplants of gut bacteria from friskier mice -- and vice versa: adventurous mice became quieter after receiving injections of gut bacteria from quieter mice.

Now Canadian researchers are testing whether similar mood changes can be achieved in humans with depression or bipolar disorder.

Dr. John Bienenstock, director of the Brain-Body Institute at St. Joseph’s Healthcare in Hamilton, Ont. recently explained to CTV that those with depression and other mental health disorders typically have signs of inflammation in their body. They hope to use probiotics to reduce that inflammation and see what happens to them mentally.

“The question is whether an attack on the inflammation level, if you can reduce that, can you actually change the psychiatric manifestations?” he said.

While the researchers don’t think probiotics will cure mental illnesses, the bacteria could help supplement medications and therapy. Results of that study are expected later this year.


There’s been lots of research looking at using probiotics to maintain digestive health, but recent research is also finding that the right kind of gut bacteria could alter the way we process our food and store fat.

In a landmark study a couple of years ago, researchers took gut bacteria from four sets of twins in which one twin was obese and the other slim. They then transplanted the bacteria into lab mice bred to be germ-free. The mice given the obese twin's gut bacteria put on weight and gained more fat than the mice given the lean twin's microbiota -- even though all the mice ate about the same amount of food.

That’s got researchers thinking that there’s something about the bacteria in the guts of obese humans that causes them to hold onto fat more than slim people.

More recently, there been a case of woman who underwent a fecal transplant to treat her recurrent C. difficile infections. The treatment worked, but the woman, who had always been slim, began putting on a significant amount of weight -- despite strict diet and exercise regimen. It turned out the woman’s fecal donor -- her daughter -- was significantly overweight, leading the researchers to suspect that the fecal transplant passed on something that made both women gain weight.

Researchers hope to one day pinpoint which bacteria strains slim people have that keep them slim, and then create probiotic supplements to repopulate these good bacteria into the guts of those with obesity.

Blood pressure

The keys to lowering blood pressure are improving fitness, quitting smoking, and eating right, but part of that eating right might include probiotics.

A recent meta-review of nine published studies on probiotics and blood pressure found a strong link between consuming fermented milks, yogurt and probiotic supplements, and a drop in blood pressure.

Most of the studies they reviewed were small and the changes in blood pressure were modest. As well, the link was strongest when several species of probiotics were consumed for at least two months or more. But the reviewers say that drops in blood pressure were similar to the results achieved by other approaches, including diet changes to cut back on salt.

It’s not clear how gut bacteria can reduce blood pressure, but it’s thought that beneficial microbes help lower “bad” LDL cholesterol and help control blood sugar.

While more research is needed before doctors can confidently recommend probiotics for high blood pressure control, the hope is that a probiotic supplement could have a role to play alongside blood pressure medications and lifestyle changes.

Skin cleanser

Beneficial bacteria don’t just live in our bodies; they live on the outside, in our skin and hair as well. But there is a growing school of thought that our obsession with hygiene and daily showering washes away these beneficial microbes, leading to skin irritation and illnesses, such as eczema and psoriasis.

One company, AOBiome, has recently launched a line of sprays made with live bacteria that it says can restore skin to its natural state and put our natural skin bacteria back in balance -- without the need for bathing.

The founders of AOBiome say there is already a family of bacteria called Nitrosomonas that feed off the urea and ammonia in our sweat, turning them into beneficial nitric oxide, which acts as an anti-inflammatory, and nitrite, which is antibacterial.

One New York Times reporter recently stopped taking showers for a month to test the Nitrosomonas-containing products. She reported that her skin was smoother, better hydrated and less prone to hormone-related breakouts, (although she never got used to having greasy hair.)

The company’s founding scientist himself says he hasn’t taken a shower in over a decade, relying only on bacteria to keep him clean.

This month, the company announced that it has just begun a phase 2 study on the use of its ammonia-oxidizing bacteria for the treatment of mild to moderate acne. The hope is that the bacteria formulation it has developed, will help control the Propionibacterium bacteria that cause acne and reduce inflammation.

The company is also working on other bacteria formulations to treat eczema, rosacea and other inflammatory skin diseases, believing that beneficial skin microbes will help restore our skin’s protective bacterial balance that our ancestors enjoyed long before anyone invented shower gel.