What are fibre supplements and what do they do?
We’ve all heard of fibre, the complex carbohydrate found in plant foods including wholegrains, fruit and vegetables. It’s essential for healthy digestion, regular bowel movements and overall good health.1
Fibre supplements contain high-fibre foods, but in supplement form – powders, granules, capsules, tablets and chewable cubes, for example. Fibre supplements can include one or a mix of the following fibre sources:
- psyllium husks
- senna leaf
- guar gum
Fibre supplements are never a substitute for a healthy diet – getting your fibre from your meals also provides other important vitamins and minerals – but some people find supplements provide a useful top-up on days when they’ve had a shortfall.
Benefits of fibre supplements
What do fibre supplements do in the body?
Just like fibre-rich foods, fibre supplements can help you have regular bowel movements, according to a 2017 study by the Mayo Clinic.2 Here’s how different types of fibre work inside the gut:3
- soluble fibre – it absorbs water, forming a gel-like substance that softens stools, and feeds the friendly bacteria in your gut. Sources include oats, nuts, seeds, fruit and veg, psyllium, inulin
- insoluble fibre – found in wheat, bran, nuts, cellulose, whole linseeds, senna leaf, chitosan and lignin, this provides bulk to help push stools through your digestive system
Many high-fibre supplements contain both types of fibre.
Upping your fibre intake guards against more than just constipation: a 2019 review in The Lancet reported that people getting the most fibre had lower blood pressure and cholesterol levels, and a reduced risk of heart disease and type 2 diabetes.7
Fibre supplements could help you manage your weight, too. A 2012 research paper in the medical journal Current Obesity Reports concluded that fibre supplements could regulate blood sugar and appetite,8 while a 2011 placebo-controlled study reported in the British Journal of Nutrition discovered that adding psyllium supplements to a normal diet lowered cholesterol levels, and reduced weight and body fat in overweight people.9
How much is safe to take?
Government guidelines recommend adults get 30g of fibre a day but this is too much for a supplement, as fibre is also found in a wide variety of foods.10 How much you need will depend on your diet but never exceed the dosage on the pack. Bear in mind that more than 40g per day of fibre from all sources can interfere with the absorption of other nutrients and some medication.11 Fibre supplements are generally safe to take,12 but can reduce the effectiveness of certain drugs, including anti-depressants, certain antibiotics and diabetes drugs, so talk to your doctor before taking.13 Also talk to your doctor first if you have digestive, gut or bowel issues, including:14,15
- a history of bowel blockage
- Crohn’s disease
- problems swallowing or a narrowing of your gullet
- unexplained changes in your bowel habits for longer than two weeks
- unexplained bleeding from your back passage
- problems passing stools despite taking laxatives
What are the side-effects of taking fibre supplements?
The most common side-effects include:16
- stomach cramps
- hard, dry stools or constipation if you don’t drink enough fluids
Side-effects are less likely if you increase your fibre intake gradually so your digestive system can adjust.17 It’s also important to drink plenty of water to help the fibre supplement digest properly and to soften your stool.18 On very rare occasions, psyllium powder preparations have caused serious allergic reactions, though this has usually been in workers involved in making the products. Seek urgent medical advice if you experience:19
- an itchy rash
- problems breathing or swallowing
- swelling of the mouth, face, lips, tongue, or throat