Do Probiotics Work? Evidence-Based Benefits & Precautions

If you suffer from digestive issues or other inflammation-related problems, you’ve probably heard that probiotics can help. We frequently hear from readers and home cooks wondering if their family could benefit from adding things like kombucha, sauerkraut, and sourdough bread into their routine for the probiotics.

Is investing in more fermented foods or probiotic supplements worth it for you? And do probiotics work? Here’s what the scientific evidence has to say about how and what these helpful bacteria can do.

What Are Probiotics?

Probiotics are the good bacteria that live in your gastrointestinal tract. They are part of the various bacteria, viruses, and other organisms that make up your gut microbiome. These living microorganisms are present in some foods and supplements, and they thrive inside the human microbiome.

Here are a few definitions of terms used to describe probiotics and their counterparts:

• Commensal bacteria, also called nonpathogenic, or non-disease-causing bacteria, aren’t harmful and, most of the time, support a healthy body. Probiotics are commensal bacteria! This is what I mean each time I refer to “beneficial bacteria” or “good bacteria.”
• Pathogenic bacteria, also known as disease-causing bacteria, are strains that challenge the body’s immune system and, if successful, cause illness and disease. That’s what I mean when I refer to “bad bacteria” or “harmful bacteria.”
• Prebiotics aren’t bacteria at all, but rather are the food source for probiotics to feast on. These fibers are found in many plant-based foods.

A quick note: There are pathogenic bacteria in every healthy body. The presence of harmful bacteria doesn’t mean you are ill; the key is that a healthy microbiome has a balanced amount of commensal and pathogenic bacteria, which lets the good stuff crowd out the bad.

How Probiotics Work

In your intestinal tract, probiotics produce vitamins and short-chain fatty acids that feed and nurture commensal bacteria that aid digestion. These microbes also help counteract and outnumber any harmful bacteria.

What Probiotics Work For, According To Science

There are tons of health benefits from a thriving probiotic community living in your digestive tract. Probiotics help break down the foods you eat, ease digestion, lower your risk of infection, support your immune system, reduce chronic inflammation, and more. 

Here are some of the most notable health benefits of probiotics, according to research. 

1. Gut Health

Without a healthy gut microbiome full of probiotics, rapidly-reproducing pathogenic bacteria can wreak havoc on your digestive system. Probiotics help balance and eliminate pathogenic and foreign bacteria in the stomach, intestines, and colon of kids and adults. 

Probiotics are healthy gut bacteria used for treatment and prevention of several digestive system problems, including:

• Constipation
• Diarrhea (especially antibiotic-associated diarrhea and traveler’s diarrhea)
• Bloating 
• Irritable bowel syndrome (IBS)
• Inflammatory bowel disease (IBD)
• Crohn’s disease
• Ulcerative colitis
• Helicobacter pylori infections

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2. Increase Nutrient Absorption

Probiotics may improve how well your body absorbs micronutrients (such as calcium and iron) from ingested foods by breaking down anti-nutrients that occur naturally in some foods.

For example, one placebo-controlled study showed that the iron status in young children was improved significantly by intake of a milk fortified with the probiotic Bifidobacterium lactis for one year.

This may be especially beneficial for malnourished individuals, including children, the elderly, and pregnant people. 

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3. Immunity

Probiotics boost the strength of immune cells and help maintain the strength of the intestinal epithelium (gut lining). This helps prevent serious and minor health conditions (from colds and flus to viruses and some cancers) by strengthening your intestine’s protective barrier against pathogenic microbes and detrimental substances.

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4. Skin Health

Some research shows that probiotics, applied topically and ingested through the gut-skin axis, may help prevent and treat certain skin issues like:

• Acne
• Eczema
• Psoriasis
• Atopic dermatitis (an allergic reaction on the skin)

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5. Vaginal Infections & UTIs

Lactobacilli, a type of probiotic, are the predominant microorganisms of the healthy human vagina. Taking probiotics and eating probiotic foods have been found to be beneficial in the prevention and treatment of vaginal infections, including female urogenital tract infections (UGTI) and urinary tract infections (UTIs). 

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6. Oral Health

Did you know that your gut microbiome isn’t the only kind you have? Your mouth, skin, and vagina (if you’ve got one) have microbiomes, too. 

Research shows that probiotics are beneficial for good oral maintenance in healthy people, due to their ability to decrease the growth of oral pathogens and contribute to a healthy oral microbiome. 

Oral probiotics are most effective when delivered directly to the mouth through probiotic lozenges, chewable tablets, or probiotic drinks. The strains most helpful for your mouth are a little different than the ones you might take for your gut.

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7. Weight Loss

While taking a probiotic doesn’t necessarily contribute to weight loss, it is recommended that people on a weight loss protocol take a probiotic in order to maintain health. Drastic alterations in energy balance, lipid metabolism, and endocrine disturbances put stress on the body, and maintaining a healthy gut microbiome can help prevent sickness during this time. 

In one clinical trial, obese patients who followed a low-carb, high-protein eating plan while taking a synbiotic (a prebiotic and probiotic together) showed no difference in body mass, BMI, waist circumstance, and body fat mass versus those taking a placebo at the end of 3 months. However, those taking the synbiotic displayed more beneficial microbial species and fewer disease biomarkers at the end of the study. 

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8. Chronic Inflammation

Probiotics play a role in maintaining the delicate balance between the body’s necessary defense mechanisms (acute inflammation) and overextended inflammatory responses (also known as chronic inflammation). 

By interacting with intestinal epithelial cells and contributing to overall good health, probiotics can help the body’s defense cells tame and target their inflammation response. 

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9. Brain And Mental Health

Studies show that probiotics and a healthy microbiome may contribute to brain health through the gut-brain axis. Probiotic supplementation could improve cognitive function and mood and they may play a role in delaying disorders of the central nervous system, such as dementia and Alzheimer’s.  

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Which Probiotics Are Most Beneficial?

The most commonly identified and used probiotic species and strains are: 

• Lactobacillus — present in many probiotic supplements, fermented foods, and breast milk
  • Lactobacillus acidophilus — common in enriched milk, yogurt, miso, and tempeh
• Bifidobacterium — used mostly in probiotic supplements 
• Escherichia
  • Escherichia coli Nissle 1917 (ECN) — one of the first probiotics identified
• Saccharomyces
  • Saccharomyces boulardii — a probiotic yeast strain with the potential advantage of being resistant to antibiotics
• Streptococcus
• Enterococcus
• Bacillus

How To Get More Probiotics In Your Diet

There are two ways to get more probiotics: by eating more probiotic foods and by taking a probiotic supplement (or both).

Probiotic foods are fermented foods including:

• Yogurt
• Kefir
• Buttermilk
• Cultured cottage cheese
• Pickled fermented vegetables
• Sauerkraut
• Kimchi
• Pickles
• Sourdough bread (although the baked bread contains no live cultures)
• Preserved lemons
• Kombucha
• Miso
• Tempeh
• Natto 

There’s a wide variety of probiotic supplements available, as well as prebiotic and synbiotic options. In general, the best options are those with clinically studied probiotic strains, as well as enzymes that help the probiotics survive digestion. 

One of the few dietary supplements we have used and recommend is Seed Probiotic, a synbiotic supplement that contains 24 strains of probiotics and prebiotics together.

Risks, Side Effects, And Precautions

Some people should avoid or limit their intake of probiotic supplements and fermented foods due to potential side effects and risks. Those include:

• people with a histamine intolerance — people who lack an enzyme called diamine oxidase (DAO)
• someone with a weakened or compromised immune system — such as someone with HIV/AIDS, cancer patients undergoing chemotherapy, and organ transplant recipients
• people with digestive disorders — someone with irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD) should consult a registered dietitian or their health care provider. In many cases, taking a probiotic or eating or even increasing fermented foods is a positive strategy for someone with digestive health disorders, though some people with extremely sensitive digestive systems may experience excess gas and bloating
• Premature infants — while taking a pediatric probiotic is often recommended for babies and toddlers, premature infants should not be given a probiotic supplement until cleared by their pediatrician due to their weaker immune systems

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