Prebiotics

Prebiotics are fibres your body cannot digest. They pass through the small intestine unchanged and reach the colon, where your gut bacteria ferment them. That fermentation is the whole point, and it is also why the first week can feel gassy. Not every fibre is a prebiotic. Psyllium mainly adds bulk and holds water, while inulin, FOS and GOS are actively eaten by bacteria such as bifidobacteria.

UK guidance puts adult fibre intake at 30 grams a day, and average intake sits far below that. A supplement is a top-up on food, not a swap for vegetables, pulses and wholegrains. Most people land here after reading about the bacteria living in the gut and wanting one measurable thing to add to breakfast.

The fibres differ more than the labels suggest

Almost every product on this page uses one of five fibre families:

• Chicory inulin: long chains, ferments slowly and deep in the colon.
• FOS (oligofructose): shorter chains from the same source, ferments faster, so gas shows up sooner.
• GOS (galacto-oligosaccharides): milk-sugar based chains, often used in small daily doses.
• Acacia fibre and partially hydrolysed guar gum: slow, mild fermenters, the usual pick for a sensitive gut.
• Resistant starch: from green banana or potato, works low in the colon.

Dose decides what you actually notice. Chicory inulin carries the one authorised European claim in this category: it contributes to normal bowel function by increasing stool frequency, at 12 grams a day. Plenty of capsule products deliver one or two grams, which is nowhere near that figure. Powders let you weigh your way up gram by gram. Note too that many supplements with live bacteria already carry a gram of FOS, so check the label before you stack two products.

How we choose the prebiotics we stock

We judge three things: the fibre itself, the grams per serving, and whether a combination adds anything. We prefer products that print the fibre name and the dose on the front, because "prebiotic blend" tells you nothing about what you are taking. Powders earn a place when you need to build up slowly, capsules when a small fixed dose is enough. We buy directly from the brands, every product passes our compliance team before it goes live, and we test products ourselves while independent labs spot-check batches. You can read how we select brands and products.

Who this suits, and who should go carefully

Prebiotic fibre fits people whose diet is short on plants, who travel often, or who want a fixed daily amount instead of guessing. Give it two to three weeks of consistent use before you judge it, and start at roughly a third of the serving on the tub. Inulin and FOS are fructans, a group many people with IBS are advised to limit, so acacia fibre or partially hydrolysed guar gum is usually the calmer starting point. If wind is your main complaint rather than regularity, a bulking fibre such as psyllium husk may suit you better than a fast-fermenting one. Drink enough water either way: fibre draws water into the bowel and works poorly without it.