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Introduction to Probiotics

Jennifer Hanes MS, RDN, LD

By now, everyone and their dog has heard about probiotics.  Mainly discussed for the health of our gut, research into probiotics as a therapeutic option is relatively new.

What are probiotics?

Probiotics, often called gut microbiota when inside your body, are bacteria, yeast, viruses, and other tiny things that live in or on your body. Bacteria are the most common and the most commonly discussed.

For the germophobes out there, this may sound terrifying. However, this is actually a good thing. The probiotics (literally translated to “for life”) form a symbiotic relationship with us. This means that both the microbiota and our bodies benefit from our coexistence.

You start picking up these good bugs as you are being born!

There are many factors that influence which bacteria thrive and which don’t. Exposure to animals, other children, playing in the dirt, and your diet can all influence your microbiota composition.

You are probably accustomed to hearing about the microbiome of your gut. However, these beneficial organisms also live in your skin, mouth, urogenital system, and lungs.

Man looking at food fermenting in jars. Fermented foods are the primary dietary source of probiotics
Photo by Micah Tindell on Unsplash

Are there probiotics in food?

Yes, yogurt is the most famous example.

But probiotics can be found in kefir, kombucha, sauerkraut, kimchi, miso paste, sourdough bread, tempeh, and fermented pickles and other veggies(those not made solely with vinegar).

Furthermore, prebiotics (or lack of them) influence what bacteria thrive in your belly. In simple terms, prebiotics are food for probiotics.  These are fiber and unsaturated fats.  

What are probiotics good for?

Research is new, but probiotics have been found to have numerous beneficial effects in the human body.

Microscopic image of bacteria, which can be a probiotic

Gastrointestinal health

Most famously, probiotics are good for gut health.  Symptoms of IBS, such as diarrhea, constipation, bloating, and gas can resolve with the use of prebiotics.

Some studies indicate that symptoms of IBD (Crohn’s and Ulcerative Colitis) can also be improved with probiotics.

Probiotics are particularly good at treating diarrhea that often results from antibiotic use.

One strain of beneficial bacteria has been shown to produce a lot of lactase, an enzyme that helps break down milk sugars. There is some speculation that this could help those that are lactose intolerant enjoy dairy again.

Bacteria and yeast in our colon contribute to the breakdown of various fibers that we eat (or should be eating) and produce vitamins (vitamin K and some B vitamins).

Finally, they produce short-chain fats that fortify our intestinal lining, drive our metabolism, and impact our GI system’s part in our immune system.

Immune system health

Some strains of probiotics appear to have a positive impact on our resistance to certain infections, particularly the common cold. 

Weight Management

Having a good balance of beneficial yeast and bacteria can help maintain a healthy body weight.

In labs, fecal transplants (yes, that’s just what it sounds like) from a healthy mouse can induce weight loss in an obese mouse, without any other changes.

Research is early days now, and particular species have not been discovered. Some seem to actually cause weight gain!

Mental Health

Many probiotics produce the exact same neurotransmitters (serotonin, dopamine, norepinephrine) that we make ourselves. There is a growing body of evidence that shows that these chemicals play a major impact on our mood and overall mental health.

Most evidence so far has looked at depression, however, anxiety, schizophrenia, ADHD, Autism Spectrum Disorder, and dementia have also been evaluated.

Psychiatric nutrition has only been around for about 10 years, and we have made rapid gains so far. This is actually my main area of focus and research outside of this blog.

Skin health

Acne, rosacea, and eczema all seem to be impacted by probiotics, both in our guts and on our skin.

A small study even showed improvements in seasonal allergies when probiotics were administered to people.

Urogenital health

Probiotics may play a role in reducing the number of urinary tract and yeast infections.

Oral Health

Probiotics may be more effective at preventing cavities and other oral diseases than some conventional measures.

Microscopic image of bacteria, which can be a probiotic
Photo by CDC on Unsplash


Are probiotic supplements safe? Who shouldn’t take probiotics?

Most likely.  You should check with your doctor before taking any supplements.

Those at most risk of problems are people with a suppressed immune system, whether this is due to illness or an effect of medications.

Newer research indicates that we should be cautious using probiotics in serious GI conditions. For instance, probiotics seem to be quite effective at preventing a flare of Crohn’s Disease and Ulcerative Colitis.

However, during a flare, probiotics may actually make the individual’s condition worse. There is similar research in Celiac Disease.

How do you pick a probiotic supplement?

I typically look for the one with the greatest number of live active cultures. I’ve had better luck managing my IBS with products that are found in refrigerators, rather than shelf-stable products.

But ultimately, they are all different and everyone probably benefits differently. 

I usually recommend picking one and taking it consistently for about 4 weeks. If your symptoms don’t resolve, try another one.

Are probiotics supplements the only way to improve your gut health?

Actually no. 

In patient studies, probiotic supplements only have a temporary effect.  Fecal transplants are actually the most permanent way to alter your gut microbiota.  This obviously isn’t done just for the heck of it, but they are a powerful option in certain conditions such as a C. Diff infection that won’t go away.

The best way to improve your gut flora is to alter your diet! 

So think of it this way.

The “good” bugs like fiber and unsaturated fats. The “bad” bugs like sugar and saturated fat.

If you were to take a probiotic supplement, then continue eating the Standard American Diet (SAD – possible, even for vegans), you are putting good bugs in, then starving them and feeding the “bad” bugs.

So feed the good guys the way you should be feeding yourself. Lots of fruits, whole grains, and vegetables.

Inulin, a fiber often found in onions, garlic, and legumes appears to be particularly good at feeding the good gut bacteria.

Limit sugar and fried foods. Cook with olive oil instead of butter and coconut oil. That way, you put the “good” bugs in and then feed them so they flourish, while also starving the “bad” bugs.

Who should be taking probiotics?

If you’ve had one of the following events or health concerns, it might be beneficial to start taking a probiotic supplement.

  • Allergies or asthma
  • Mood disorders
  • IBS, IBD, or another chronic gastrointestinal diagnosis
  • Food poisoning or “stomach flu”
  • You’ve been on antibiotics
  • You have certain inflammatory conditions
  • You are ill frequently

Do probiotics make you poop?

Probiotics are known to help regulate stool frequency and consistency. Meaning they can help alleviate both diarrhea AND constipation.

When should I take probiotics?

Some evidence suggests that probiotics are best taken on an empty stomach. This usually means 1 hour before you eat and at least 4 hours after your last meal/snack.

Are there side effects to taking probiotic supplements? What about eating probiotic foods?

When first taking a probiotic, some people experience some intestinal discomfort including bloating, gas, and increased thirst. This is usually temporary as the overall microbiome adjusts.

Probiotic foods are generally considered safe.

However, those that follow a low tyramine diet for migraine prevention or as part of a requirement for certain medications, will notice that many foods high in probiotics are high in tyramine.

What are synbiotics?

Synbiotics are products that contain both probiotics (the “good” bacteria) along with prebiotics (the food for the probiotics).

You may also see the word postbiotic. These are compounds created by probiotics through their normal metabolic processes that do good things for us all on their own. The most commonly talked about postbiotic is butyrate.

Jenn in a grey and white half sleeved shirt in front of a beige wall and a abstract city painting

Jennifer Hanes MS, RDN, LD is a registered dietitian, mom, wife, and vegetarian in North Texas. She has dedicated Dietitian Jenn to be a source of information, ideas, and inspiration for people like her, vegetarians that live with people with different dietary beliefs and/or needs in a multivore household.

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