Probiotic
Probiotics
This article is written from cited public sources but has not yet been signed off by a qualified expert. Use it as general background only, and check important details with a health professional.
Probiotics are live microbes that can benefit health when taken in the right amounts. Their effects depend on the exact strain. Evidence is good for a few specific uses and weak for many others. They are not a nutrient, and there is no daily requirement.
What is Probiotics?
Probiotics are live microorganisms that, when taken in adequate amounts, give a health benefit. They are mostly bacteria, but some are yeasts.[1]
They are named by genus, species and strain (for example, Lacticaseibacillus rhamnosus GG). Effects are often specific to a strain, so results for one product do not apply to another.[1]
Prebiotics are different: they are fibres that feed gut microbes. Products with both are called synbiotics.[1]
Its role in the body
- Probiotics act mainly in the gut. They may help by competing with harmful microbes, supporting the gut lining and interacting with the immune system; some effects are shared, others are strain-specific.[1]
- They may live in the gut only for a short time, and the pattern differs from person to person.[1]
Important food sources
- Curd (dahi) and yoghurt with live culturesMade with live bacteria; some products also contain added probiotic strains (check the label).
- Buttermilk (chaas) and other uncooked fermented foodsCan contain live microbes, but most fermented foods have not been shown to contain proven probiotic strains. Foods cooked after fermenting, such as idli and dosa, or pickles processed after fermenting, do not contain live cultures when eaten.
- Probiotic-fortified drinks and foodsShould name the strain and number of live microbes (CFU) on the label.
Recommended dietary intake
| Group | Amount | Basis | Region |
|---|---|---|---|
| All adultsProbiotics are not essential nutrients and have no recommended intake. Suitable strains and amounts depend on the purpose and should follow evidence for that strain and a clinician’s advice. A higher CFU count does not mean a product works better. | Not established[1] | NOT ESTABLISHED | International |
Signs sometimes associated with low levels
- There is no "probiotic deficiency". Gut microbes vary widely between healthy people, and no single healthy pattern has been defined for everyday use.[1]
Why symptoms alone cannot confirm a deficiency
Bloating, gas, loose stools or constipation are common and have many causes, including diet, infections, food intolerances, medicines and bowel conditions. They do not show that you need a probiotic.
Ongoing bowel changes, blood in stools, weight loss or severe pain need a doctor’s assessment.
Tests a clinician might consider
- There is no routine clinical test to decide whether someone needs a probiotic. Clinicians test for specific conditions (for example infections) based on symptoms.[1]
Who is more likely to have low intake
- People taking antibiotics are at risk of antibiotic-associated diarrhoea; risk is higher in hospital, in children under 2 and in adults over 65. A clinician may consider specific probiotics in some of these cases.[1]
Potential benefits and quality of evidence
- Certain strains (Lacticaseibacillus rhamnosus GG or Saccharomyces boulardii), started within 2 days of antibiotics, help reduce antibiotic-associated diarrhoea in children and adults aged 18–64.[1] Moderate evidence
- Probiotics may give a modest improvement in irritable bowel syndrome (IBS) symptoms, depending on the strain and symptom.[1] Limited evidence
- Some strains may lower the risk or severity of eczema (atopic dermatitis) in infants and children, but relief is limited and effects vary by strain.[1] Limited evidence
- Evidence for lowering cholesterol or helping weight loss is mixed and not enough to recommend probiotics for these purposes.[1] Not enough evidence
Side effects
- In healthy people, probiotics are unlikely to cause harm, and side effects are usually minor.[1]
Risks of too much
- Rarely, probiotics have been linked to serious bloodstream infections (bacteraemia or fungaemia), mostly in people who were severely ill or had weak immune systems.[1]
- Many safety questions are not well studied because trials were not designed to look at harms. Labels that list the number of microbes only at manufacture may overstate how many are alive when you use the product.[1]
Medicine and supplement interactions
- Medicines that weaken the immune system (e.g., chemotherapy, high-dose steroids, transplant medicines): People with weakened immunity are at higher risk of rare serious infections from probiotics and should use them only with their doctor’s agreement.[1]
- Antibiotics: Specific probiotics are sometimes used alongside antibiotics to reduce diarrhoea; discuss timing and choice with the prescriber.[1]
Never start, stop or change a prescribed medicine because of this list — talk to your doctor or pharmacist.
Pregnancy and breastfeeding
- Some studies gave probiotics in pregnancy to reduce eczema risk in children, with mixed results. Ask your doctor before using probiotic supplements in pregnancy. Probiotics for premature infants are a hospital medical decision; the US FDA has raised safety concerns about this.[1]
Kidney and liver cautions
- People who are seriously ill, including those with advanced liver or kidney disease, are among those in whom rare serious infections have been reported; they should only use probiotics on medical advice.[1]
Upper intake limits
There is no upper limit for probiotics because they are not nutrients with official intake values. Safety depends on the strain, the product and the person’s health.[1]
When to talk to a professional
Talk to a doctor or registered dietitian before starting a supplement, especially if you are pregnant or breastfeeding, have a long-term illness, or take any regular medicines.
Do not start, stop or change a prescribed medicine because of anything you read here.
Supplements sold without a prescription are not automatically safe. Doses, quality and interactions still matter.
Seek medical care promptly if you have severe, sudden or worsening symptoms.
If you have a weakened immune system, a central line, are seriously ill, or are buying probiotics for a premature or sick infant, speak to a doctor first.
Choose products that list the full strain name and the number of live microbes through the expiry date.
References
- NIH Office of Dietary Supplements. Probiotics — Fact Sheet for Health Professionals (opens in a new tab) (2025-03-25). Accessed 9 Oct 2026.
Sources checked: 9 Oct 2026
This page is general education, not personal medical advice. For diagnosis, treatment or medicines, please talk to a qualified doctor, registered dietitian or pharmacist. Read our medical & AI disclaimer.