The Gut Health Supplement Guide: Fibre, Clay And Bacteria

Most bottles mix at least two of the three. McRorie and McKeown on the physics of functional fibres make the point that matters most: only fibre that resists fermentation and reaches the large bowel intact produces a laxative effect, and some fibres can be constipating.

Mechanism from McRorie and McKeown 2017; the evidence column from the two reviews cited below.

The figure a supplement is judged against is not on any supplement label. The NIDDK puts the whole-diet target at 22 to 34 grams of fibre a day for adults, with two conditions dropped more often than the number itself: drink plenty of liquid so the fibre can work, and build the intake up gradually.

The federal health-claim doses sit in the same territory. 21 CFR 101.81 sets the qualifying intakes at 3 grams a day of beta-glucan from whole oats or barley, and 7 grams a day of soluble fibre from psyllium seed husk. The trial built on that dose had 68 adults eat four servings a day for a month, about 8 grams of extra soluble fibre, for a 2.1 per cent fall in total cholesterol — which the authors themselves call relatively small.

So the intakes that moved something are grams a day: 10 for psyllium in constipation, 7 for the federal claim, 3 for beta-glucan, 20 for flaxseed, 100 for dried plums, every one delivered in food or in a measured powder. A capsule can be set beside those figures the moment its panel prints grams, and where a panel gives a blend total instead the comparison cannot honestly be made in either direction.

A Supplement Facts panel must name what is in the product and give a serving size. A proprietary blend lets a maker give one total instead of a figure per ingredient, which is legal and is also the single biggest gap a buyer meets.

The second guide turns that into a checklist.

The NIH Office of Dietary Supplements describes a normal panel as one listing the active ingredients, the amount per serving and the other ingredients. Read it in that order and four things come out in under a minute: how much is a serving, how many servings the bottle holds, how much of each ingredient is in one, and what makes the capsule a capsule.

A blend changes exactly one of those four. The names stay, the total stays, the split disappears. What survives is an arithmetic ceiling: if eight names share 1.5 grams, no one of them is above 1.5 grams. A blend cannot hide the names, the serving size, the allergen statement or the maker’s address.

Two federal facts frame the rest: the FDA has no authority to approve a dietary supplement before it is marketed, and no rule caps the amount of an ingredient in a serving.

Bentonite clay is a mined mineral sold as an adsorbent, and the published literature on swallowing it is not about whether it works. A Dutch survey assayed 63 clays sold for oral use and found lead as high as 99.7 mg/kg and arsenic as high as 45.1 mg/kg. Two of the 27 health clays would take a user past the toxicological limit for lead, and 11 of the 27 past it for inorganic arsenic; the authors conclude that use should be discouraged, particularly in pregnancy. The FDA has separately warned consumers off one such clay over elevated lead, and since its English page no longer resolves, the Spanish-language version is what this desk cites.

Aloe vera travels beside clay more often than anything else, and needs one distinction. NCCIH records that in 2002 the FDA required manufacturers to remove aloe latex from over-the-counter laxative products for lack of safety data, and that aloe products are made from different parts of the leaf: gel, latex or whole crushed leaf. On the gel, three randomised trials in 151 patients found short-term improvement in irritable bowel symptom scores against placebo, at a dose the pooled abstract never publishes.

Almost every useful trial here ran a month or longer. The constipation meta-analysis found its effect only at four weeks or more, the graded review counted nothing shorter at all, the flaxseed trial ran twelve weeks and the dried plum trial three on each arm.

So the honest expectation for any fibre product is that the first week tells you about tolerance and the first month tells you about effect. That has a commercial consequence too — a guarantee shorter than the evidence window closes before the product has had a fair run.

1. Liquid, every dose. MedlinePlus calls psyllium a bulk-forming laxative and says you must drink at least 8 ounces, 240 millilitres, of liquid with it.
2. The swelling warning. The federal rule covering water-soluble gums in over-the-counter drugs, 21 CFR 201.319, names psyllium and glucomannan and requires a warning that taking the product without adequate fluid may cause it to swell and block the throat or oesophagus, and that it should not be taken by anyone with difficulty swallowing. A supplement sits in a different regulatory category, so that is the rule on the ingredient rather than a quotation from any bottle.
3. The cause, before the remedy. The National Institute on Aging notes that a range of ordinary medicines can cause constipation, naming antacids containing aluminium or calcium, antihistamines, certain painkillers, blood-pressure medicines and diuretics. If the change started when a prescription did, pull that thread first.
4. The allergen line. Botanical blends here routinely include tree nuts, and FDA rules require the specific nut to be declared. Read it before the front of the bottle.

There is a line, it is federal, and it is sharper than most labels in this aisle suggest. A supplement may make a structure and function claim, a statement about how an ingredient acts on the body, and the FDA’s own example of one is fiber maintains bowel regularity — which is also the register this whole category should be written in.

What it may not do is claim to treat, cure or prevent a disease, because only a drug can lawfully make that claim. The Federal Trade Commission puts the reader-facing half more bluntly: no one can promote dietary supplements for the treatment of a disease. In advertising the standard is substantiation, and a health claim requires competent and reliable scientific evidence behind it.

• Grams per serving for every fibre named, not a blend total. It is the figure that lets a reader set a product against a research intake.
• The soluble and insoluble split, because the two do different jobs.
• Genus, species and strain for any organism, with a colony count guaranteed to the end of shelf life, and the capsule shell material named on the Other Ingredients line.
• An allergen statement and a facility statement, kept separate. One is about the recipe, the other about the room.
• A lot number and a route to a certificate of analysis, especially where a mined mineral is on the panel.

That list is the skeleton of the eight-point checklist, which runs the same standard against a real panel.