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What Are Probiotics?
Updated on August 13, 2023
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What Are Probiotics?

Probiotics, or good gut bacteria, are live microorganisms that maintain the gastrointestinal microbial ecosystem.1 Their functions include:2

  • Vitamin synthesis
  • Digestion and absorption assistance
  • Infection prevention
  • Immunity stimulation

Probiotics offer several gut health benefits. These include improved digestion and immunity, as well as mental well-being.

Several sources provide probiotics. Fermented foods such as yogurt, kefir, sauerkraut, and kimchi3 are great sources of probiotics.4

Probiotics are also available as dietary supplements through various strains and doses.5 They come in several forms, such as capsules, powders, and liquids.

“The most widely used probiotics are Lactobacillus, and Bifidobacterium, and Saccharomyces,” says our in-house medical expert, Dr. Rizza Mira.

Most Common Types of Probiotic Bacteria

Several common types of probiotic bacteria offer significant gut health benefits. They are typically identified by their specific strains.5 The general evidence on the effectiveness of these probiotic strains still requires further research.

The most common microbial organisms found in probiotic products include:

  • Lactobacillus
  • Bifidobacterium
  • Saccharomyces
  • Streptococcus
  • Enterococcus
  • Escherichia
  • Bacillus

Lactobacillus and Bifidobacterium are the most common genus found in probiotic products.6 They come in several strain variations.

Research has found that the benefits of these probiotics range from the following:6

  • Treatment of infant colic and infections
  • Improved lactose and vitamin digestion
  • Prevention and treatment of dental disorders
  • Prevention of allergic reactions in children
  • Lowered cholesterol levels
  • Improved weight loss

For instance, Lactobacillus is a group of bacteria commonly found in commercial products. They have been used for centuries in the production of dairy products such as yogurt.

Lactobacillus produces lactic acid. Lactic acid helps colonize bad bacteria in the digestive tract, the mouth, and the vagina.

On the other hand, Bifidobacterium are the first colonizers of infant gut microbiota. Newborns can receive some Bifidobacterium strains through breastfeeding.

Bifidobacterium has several functions, such as:

  • Lactose digestion
  • Prevention and reduction of diarrhea
  • Improved lipid levels
  • Decreased symptoms of irritable bowel syndrome (IBS)

Other strains of Bifidobacterium can also synthesize B vitamins, vitamin C, and vitamin K.

Bifidobacterium can also promote mineral absorption by controlling stomach acidity.

The effects and outcomes of probiotic use may vary. These depend on individual factors and the specific probiotic strains consumed.

How Long Should You Take Probiotics?

A common concern shared by people is about determining the optimal time frame for taking probiotics. 

The effects of probiotics manifest depending on various factors. It can take anywhere from 2-3 weeks or 6-8 weeks before you see results.7 

“This number depends on factors such as age, medical conditions, and the degree of inflammation in the gut,” says Dr. Mira.

However, some people may take probiotics for 6-8 weeks and notice no results. If this is the case, stop taking probiotics or seek professional help.8

Certain health conditions can also determine how long you should be taking probiotics.

What does the research say?

Scientists are still determining when and how probiotics should be used. They are also determining how effective probiotics are.9 However, several studies have shed light on this topic.

Some studies suggest that probiotic intake must be continuous. This can help maintain their beneficial effects.

A review examined individuals with IBS who took probiotics. They found that the individuals experienced benefits from probiotics from eight weeks onwards.10

Another study compared those who drank a high-dose probiotic drink for 12 weeks to a placebo group.11 Participants who drank probiotics had reduced incidence of upper respiratory infection. 

These studies indicate that regular probiotic supplementation may sustain probiotic population in the gut.

On the other hand, certain studies have shown positive effects even when taking probiotics for a short period of time.

A systematic review found that probiotics could reduce acute diarrhea by 25 hours.12 More research needs to determine who will benefit from probiotics and how cost-effective it is as a treatment.

Overall, the duration of probiotic intake may vary depending on several factors. These include specific health conditions, probiotic strains, and individual factors.

Individual factors affecting probiotic use duration

You should take probiotics consistently to reap their benefits and effect. However, certain factors can affect how long and how often you should be using probiotics.

Individual factors that play special importance in taking probiotics include:

  • Age
  • Biological sex
  • Medical conditions
  • Use of other medications (some may disrupt the microbiome)

For example, health conditions can impact the duration of probiotic use.

Acute conditions may require short-term use. For example, acute diarrhea has been shown to improve within days of probiotic supplementation.7 

“This may range from one to two weeks on average, but can change,” says Dr. Mira.

Certain medications, like antibiotics, may also create an unbalanced gut microbiome diversity. Chronic stress, IBS, or small intestinal bacterial overgrowth (SIBO) can worsen gut microbiome conditions.

Discuss with your healthcare professional how often you should use probiotics, if at all.

If you began taking probiotics and have seen improvements, continued use is recommended.

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How Long Before Probiotics Start Working?

The timeframe for probiotics to start taking effect can vary depending on several factors. Understanding these factors can provide a general idea of when probiotics can start working.

How quickly do they work?

Individual responses to probiotics can vary. Some people may experience noticeable improvements within a few days. Others may require several weeks of consistent use before seeing results.

Generally, it can take 2-3 weeks before seeing significant results from probiotic supplements. 

It will take time for the good bacteria to start to repopulate and sustain the balance. This will also allow for some inflammation to decrease to start seeing improvement in symptoms,” says Dr. Mira.

For others, it can take 6-8 weeks before you notice meaningful changes.8

It also depends on different factors, such as gut health and balance or inflammation.

Certain conditions can also influence how quickly results manifest. 

For example, researchers found that probiotic supplements help acute diarrhea within a few days.7  Another study found that probiotics can improve severe constipation within four weeks.

Other factors that can influence how fast results can manifest include:7

  • Poor gut health
  • Chronic stress
  • A poor diet
  • Regular antibiotic use 
  • Using the incorrect probiotic strain and dosage
  • Improper storage
  • Using expired probiotics

If you have been using probiotics for weeks and have not noticed any results, it may be best to stop taking them and consult your doctor.8

How to Monitor the Effectiveness of Your Probiotic Supplements

Monitoring the effectiveness of probiotic supplements is essential. It helps gauge their impact on both your gut health and overall health. Its effect on overall mental health may take a longer time.

Individual responses to probiotic supplementation may vary. However, several signs can indicate whether probiotics are working for you.

How to Know If a Probiotic Works for You

Individual responses to how probiotics work can vary, and it may take time to notice the desired effects. It is important to be patient and consistent in your probiotic regimen.

Here are a few positive changes to look out for:

  • Digestive health changes – One of the primary benefits of probiotics is improving digestive health.8 If your probiotic is effective, you may notice positive changes in your digestive system. These can include reduced bloating, reduced stomach pain, and improved regularity of bowel movements.
  • Symptom improvement – You may notice improvements in symptoms during probiotic supplementation. For example, taking probiotics for IBS may reduce abdominal pain, bloating, and stool frequency.13
  • Enhanced immune system – Probiotics can support immune system health by modulating the immune response. For example, women may experience a reduced frequency of bacterial vaginosis.8 Probiotics also shorten diarrhea and hasten recovery in those with gut infections.
  • Increased well-being – Some individuals report a sense of well-being when taking probiotics. Research has found that probiotics can improve mood, sleep quality, and cognitive function.14

What to Do if Probiotics Aren't Working

There are several reasons why probiotics may not be working. These can include:15

  • The strains you’re taking are dead
  • The strains you’re taking can't survive in your digestive tract
  • Wrong way of taking probiotics (some can be added in liquids while others are taken directly as tablets/capsules)
  • Inconsistent usage of probiotics
  • Using the wrong strains

There are several steps you can take if you have been taking probiotics and haven't observed the desired effects:

  • Consult a healthcare professional – Consider discussing your probiotic use with a healthcare professional. They can provide guidance, evaluate your gut microbiome or immune system, and adjust your probiotic regimen.
  • Try a different probiotic strain or brand – Not all probiotics are the same. Different strains may have varying effects on individuals. Try a different strain or brand of probiotic to see if it produces more favorable results for you.
  • Adjust the dosage – Sometimes, the dosage of probiotics may need to be adjusted to optimize their effects. Your healthcare professional can adjust the dosage based on your specific needs.
  • Give it more time – Some probiotics may take longer to exhibit noticeable effects, especially if you are addressing a chronic health condition. Continue taking probiotics consistently before concluding that they are not working.

How to Choose the Right Probiotic for You

Choosing the right probiotic for your needs is crucial to maximizing its potential benefits. Know your health goals, choose the right products, and get probiotics from diverse sources.

The following section will offer tips on how you can choose the right probiotic for you.

Ensuring Your Probiotic Will Work

To get the most out of your probiotics, consider these helpful tips:

  • Specific health goals – Determine your specific health goals or concerns. Identifying your health goals will help you select a probiotic that aligns with your needs.
  • Strain of probiotics – Some types of probiotics may help with one problem but not with other problems.16 Research the strains that have been studied and shown benefits for your specific health goal. 
  • Product quality and brand reputation – Pharmaceutical-grade probiotics have significant differences from commercial products. These include yogurt and probiotic supplements.16 Choose from reputable brands or manufacturers known for their commitment to quality and safety.17
  • Individual dietary restrictions or preferences – Consider any dietary restrictions or preferences you have. These might range from vegetarian or vegan diets, gluten intolerance, or lactose intolerance. Check the product labels carefully.
  • Product storage and handling – Probiotics are living microorganisms. They can be sensitive to environmental factors. Pay attention to the storage instructions on the product packaging. Make sure that the probiotic remains viable.18 Some probiotics require refrigeration, while others may be shelf-stable.
  • Appropriate dosing – Follow the recommended dosage instructions by the manufacturer or your healthcare professional.
  • Probiotic foods vs. probiotic supplements – Fermented foods allow healthy bacteria to thrive. However, be mindful of added ingredients such as sugar to probiotic foods.3 

Potential Risks and Side Effects of Probiotics

Probiotics are generally considered safe, especially for healthy individuals.9 

However, exercise caution when taking probiotics if you experience any of the following:

  • A weakened immune system
  • A critical illness
  • Underwent a recent surgery 

“Remember that the Food and Drug Administration does not regulate probiotics as a medicinal product. Consult your healthcare professional if you have other conditions,” cautions Dr. Mira.

Individuals who first use probiotics may experience minor self-limited gastrointestinal symptoms.5 These range from gas, bloating, or diarrhea. This is due to changes occurring in the gut microbiome.

These side effects should last from a few days to a few weeks. 

On rare occasions, probiotics can give rise to other adverse side effects. These include: 

  • Infection
  • Antibiotic resistance
  • Imbalanced gut microbiome or weakened gut health
  • Weakened immune system
  • The development of harmful byproducts from probiotic supplements9

Other rare cases of side effects from probiotics include skin issues such as rashes or itchiness. Consider if you are allergic to gluten, soy, eggs, dairy, or lactose. Consult your healthcare provider before taking probiotics.

It's important to note that many people take probiotics and don’t suffer from any side effects.

We advise you to consult a healthcare professional for proper evaluation and guidance. This is important if you experience unusual symptoms after starting probiotics.

Incorporating Probiotics into Your Lifestyle

There are several ways that you can incorporate probiotics into your daily routine. 

  • Dietary sources of probiotics – Consuming fermented foods can provide natural sources of probiotics.3 Adding these foods to your diet can contribute to a diverse and healthy gut microbiome.
  • Balanced and varied diet – A diet rich in whole foods, fiber, fruits, and vegetables supports a healthy gut. Include a diverse range of plant-based foods in your meals to nourish the beneficial bacteria in your gut.19
  • Manage stress – Chronic stress can increase gut barrier permeability. This disrupts the balance of the gut microbiota.20 Stress-reducing activities can support healthy gut microbiota. Consider activities such as regular exercise, meditation, or spending time in nature.
  • Avoid excessive use of antibiotics – Antibiotics can disrupt the balance of gut bacteria. It does this by removing not only harmful bacteria but beneficial strains too.21 Use antibiotics judiciously and only use them when necessary to minimize their impact on the gut microbiota.

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Updated on August 13, 2023
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21 sources cited
Updated on August 13, 2023
  1. Microorganisms with Claimed Probiotic Properties: An Overview of Recent Literature”. National Library of Medicine.
  2. Typical intestinal bacteria”. Otsuka Pharmaceutical Co.
  3. Gut Health Foods - 15 Foods For Good Gut Health”. Benenden Health. 
  4. Probiotics: What You Need To Know”. National Center for Complementary and Integrative Health.
  5. Probiotics”. National Institutes of Health.
  6. The 10 Most Common Types of Probiotics (and Their Benefits)”. OMNi-BiOTiC®.
  7. How Long Does It Actually Take For Your Probiotic To Start Working?”. Mbghealth.
  8. How to tell if your probiotics are working”. ZOE.
  9. Probiotics”. Cleveland Clinic.
  10. Probiotics in Irritable Bowel Syndrome: An Up-to-Date Systematic Review”. National Library of Medicine.
  11. Prospective study of probiotic supplementation results in immune stimulation and improvement of upper respiratory infection rate”. KeAi.
  12. Probiotics for treating acute infectious diarrhoea”. National Library of Medicine.
  13. Probiotics in Irritable Bowel Syndrome: A Review of Their Therapeutic Role”. National Library of Medicine.
  14. Effects of Probiotics on Cognitive Reactivity, Mood, and Sleep Quality”. National Library of Medicine.
  15. 5 Reasons Your Probiotics Aren't Working And What To Do About It”. hyperbiotics.
  16. Probiotics”. National Health Service UK.
  17. How To Pick the Best Probiotic”. Cleveland Clinic.
  18. Probiotics in Food Systems: Significance and Emerging Strategies Towards Improved Viability and Delivery of Enhanced Beneficial Value”. National Library of Medicine.
  19. Gut Bacteria”. Physicians Committee for Responsible Medicine.
  20. Stress, depression, diet, and the gut microbiota: human–bacteria interactions at the core of psychoneuroimmunology and nutrition”. National Library of Medicine.
  21. Impact of antibiotics on the human microbiome and consequences for host health”. National Library of Medicine.
Dr. Rizza Mira
Dr. Rizza Mira
Medical Reviewer
Dr. Rizza Mira is a medical doctor and a general practitioner who specializes in pediatrics, nutrition, dietetics, and public health.

As a pediatrician, she is dedicated to the general health and well-being of children and expecting parents. She believes that good nutrition, a healthy lifestyle, and prevention of illness are key to ensuring the health of children and their families.

When she’s not in the hospital, Rizza advocates and mobilizes causes like breastfeeding, vaccination drives, and initiatives to prevent illness in the community.
Will Hunter
Will Hunter
Content Contributor
Will is a content writer for KnowYourDNA. He received his B.A. in Psychology from the University of California, Los Angeles. Will has 7 years of experience writing health-related content, with an emphasis on nutrition, alternative medicine, and longevity.
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