Gut Health Supplements: Probiotics, Psyllium and What Research Says
What probiotics and psyllium fibre can and can't do for your gut, how strong the evidence is, how to read a probiotic label and how to take psyllium safely.
6 min read
The best-supported gut supplements are psyllium fibre for constipation and certain probiotics for lowering the chance of diarrhoea during antibiotics. For IBS, probiotics may help some people, but research can't yet say which strains work best. Probiotic effects depend on the strain, so choose products that name it, and take psyllium with plenty of water.
"Gut health" covers a lot of products. This guide focuses on the two with the most research behind them, probiotics and psyllium, and on what the evidence does and doesn't show.
What are probiotics and how are they labelled?
Probiotics are live microorganisms, identified by genus, species and strain. A full name includes an alphanumeric strain code after the species, and common products contain organisms such as Bifidobacterium, Saccharomyces and members of the Lactobacillaceae family[1]. The strain matters because research results apply to the specific strains tested.
The number on the front is in colony-forming units (CFU), the count of live cells. Many products contain 1 to 10 billion CFU per dose, and some 50 billion or more, but a higher CFU count is not necessarily more effective[1]. The NIH also notes that the wide range of strains, doses and inconsistent labelling make it hard to tell which products have verified benefits[1]. Our guide to reading a supplement label covers the rest of the panel.
Do probiotics actually work?
For some uses there is moderate evidence; for many others, it's uncertain. A summary of the main findings:
| Use | What studies found |
|---|---|
| Diarrhoea linked to antibiotics (adults) | A 2017 review of 17 studies in people not in hospital found probiotics were linked to about half the chance of antibiotic-associated diarrhoea; the conclusion was tentative because study quality was only moderate[2]. |
| Diarrhoea linked to antibiotics (children) | A Cochrane review of 33 studies found diarrhoea in 8% of children given probiotics vs 19% of controls (moderate-certainty evidence). Higher doses (5 billion CFU or more a day) appeared more effective[3]. |
| C. difficile diarrhoea | A 2017 analysis of 31 studies, mostly in hospital patients, concluded with moderate certainty that probiotics can reduce the risk in people taking antibiotics[2]. |
| Irritable bowel syndrome (IBS) | A 2018 review of 53 studies found probiotics may help overall symptoms and abdominal pain, but couldn't say which species or strains are most likely to help[2]. |
| Constipation | A 2014 review of 14 studies in adults showed some evidence of benefit[2]. |
For IBS, the NHS suggests trying probiotics for a month, as they may help symptoms caused by changes in gut bacteria[4]. If you take probiotics alongside antibiotics, see can I take probiotics and antibiotics together for timing.
Are probiotics safe?
For healthy people they have a long history of apparently safe use, but the risk is higher for people who are seriously ill or have weakened immune systems. NCCIH notes that few studies have looked at safety in detail, and that severe or fatal infections have been reported in premature infants given probiotics[2]. In the Cochrane review in children, adverse events were uncommon and none of the trials reported serious adverse events attributable to probiotics[3]. If you are immunocompromised, very unwell or buying for a premature baby, speak to a doctor first.
What does psyllium do?
Psyllium is a bulk-forming fibre laxative: it absorbs liquid in the gut, swells and forms a softer stool that is easier to pass[5]. In the UK it's sold as ispaghula husk, best known as Fybogel; the European Medicines Agency notes that ispaghula husk is also known as Plantago ovata, ispagol and psyllium[6].
- Constipation: the NHS says it usually takes 2 or 3 days to work; the main side effects are wind and bloating[7].
- IBS: the EMA found the data insufficient to prove benefit for IBS in general, with some benefit in constipation-predominant IBS, where it is recommended as an add-on[6]. The NHS lists soluble fibre and laxatives such as Fybogel among options for IBS constipation[4].
- Cholesterol: doctors sometimes prescribe psyllium for high cholesterol[5]. In the US, foods may carry an FDA-authorised claim that 7 g or more a day of soluble fibre from psyllium husk, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease[8].
More detail is in the psyllium guide.
How should I take psyllium?
Always with plenty of liquid, and away from other medicines. MedlinePlus says to mix powder or granules with 8 ounces (240 ml) of liquid and to drink at least that much when you take it[5]. The NHS advises adults taking Fybogel to drink more than 2 litres of fluid a day, and to take the evening dose at least an hour before bed[9].
Fibre can change how other medicines and supplements are absorbed. The NHS advises taking other medicines, vitamins or supplements more than an hour before or after it[10]. MedlinePlus says not to take digoxin, aspirin or nitrofurantoin within 3 hours of psyllium[5]. The NHS also names lithium, carbamazepine, insulin and other diabetes medicines among those to mention to your pharmacist[10].
Tell your doctor before starting if you have diabetes, kidney disease, intestinal blockage, rectal bleeding or difficulty swallowing, or are pregnant[5]. MedlinePlus advises not taking it for constipation for longer than a week unless a doctor tells you to[5].
Is fibre from food better than a supplement?
Food comes first, and a supplement can help close the gap. UK guidance is 30 g of fibre a day for adults, while most adults eat about 20 g. Eating plenty of fibre is associated with a lower risk of heart disease, stroke, type 2 diabetes and bowel cancer, and it helps prevent constipation[11]. Wholegrains, potatoes with skins, pulses, vegetables, fruit, nuts and seeds all count[11].
When should I see a doctor instead?
See a GP if diet changes and pharmacy medicines aren't helping your IBS symptoms, or if you need to avoid lots of foods to control them[4]. With psyllium, talk to a doctor if constipation hasn't improved or gets worse after 3 days[9], and call your doctor straight away if you have difficulty breathing or swallowing, stomach pain, a rash, itching, nausea or vomiting after taking it[5].
How Suppin helps
- The Digestive comfort plan builds a routine by fixed safety rules from your goals and health answers, with a reason for each product.
- Scan a probiotic or fibre product with the scanner (barcode or label photo) to see its quality score out of 10 and whether it suits you.
- Schedule psyllium and your other products by part of the day, so fibre isn't taken at the same time as medicines and minerals.
- Reminders at your times, plus a refill heads-up before you run out.
Get Suppin on the App Store to build a gut routine you can keep to.
FAQ
There's no single best strain. Results apply to the strains tested, and for IBS a large review couldn't identify which species or strains are most likely to help[2]. Choose a product that names the strain and follow its label.
Not necessarily. The NIH says products with higher CFU counts are not necessarily more effective[1], although a Cochrane review in children found doses of 5 billion CFU or more a day worked better for antibiotic-associated diarrhoea[3].
For constipation, MedlinePlus advises not using it for more than a week unless a doctor says so[5]. The NHS notes a doctor may recommend it for many months for more serious constipation or to raise fibre intake[9].
Leave a gap. The NHS advises taking medicines, vitamins and supplements more than an hour before or after ispaghula husk[10].
Not for everyone. The risk of harm is greater in people with severe illness or weakened immune systems, and in premature infants[2].
Sources
- NIH Office of Dietary Supplements — Probiotics fact sheet
- NCCIH — Probiotics: Usefulness and Safety
- Guo Q, Goldenberg JZ, Humphrey C, El Dib R, Johnston BC. Probiotics for the prevention of pediatric antibiotic-associated diarrhea. Cochrane Database Syst Rev, 2019
- NHS — Diet, lifestyle and medicines for IBS
- MedlinePlus — Psyllium
- European Medicines Agency — Assessment report on Plantago ovata Forssk., seminis tegumentum (ispaghula husk), 2013
- NHS — About Fybogel (ispaghula husk)
- FDA, 21 CFR 101.81 — Health claims: soluble fiber from certain foods and risk of coronary heart disease
- NHS — How and when to take Fybogel
- NHS — Taking Fybogel with other medicines and herbal supplements
- NHS — How to get more fibre into your diet
Educational information, not medical advice. Check with your doctor or pharmacist before starting or changing supplements, especially if you take medication, are pregnant or have a health condition.
