XOS is in Femme Flora as the fibre paired with its live cultures. We chose it over other fibres for three reasons: it has been studied at lower intakes than FOS, it is generally better tolerated, and it is plant-derived.

Those reasons are about choosing the right fibre, not a claim about what 250mg does on its own. The rest of this page is about the amount, and why it is what it is.

Xylo-oligosaccharides — XOS — are short chains of xylose sugar units, made by breaking down the fibre in plant material with an enzyme. Ours is derived from corncob. They are classed as a fibre that the human gut cannot digest, which instead reaches the large intestine intact.

They are a regulated novel food in Great Britain, authorised under a specific production route — corncob substrate, hydrolysed with a xylanase enzyme, then purified. The authorisation sets a maximum of 2g a day in food supplements, and requires the label to read “Xylo-Oligosaccharides” in that exact form. Our 250mg is comfortably inside the limit.

Both parts are confirmed. Our manufacturer has confirmed in writing the corncob substrate and the production route: hydrolysis with a xylanase enzyme from non-GM Trichoderma reesei, then purification, giving more than 95% XOS. That is the route the authorisation covers.

The honest answer is that a capsule is a small place. A daily serving of Femme Flora is two size 0 capsules, and they already hold 50 billion live cultures, 150mg of cranberry extract, four vitamins and the XOS. Reaching 1.4 grams of XOS would need roughly two to three additional capsules for the fibre alone.

That is a real constraint, and it is why the amount is set by what the capsule can hold alongside the cultures rather than by the standalone trials. Section 4 explains the reasoning for including it anyway, and where its limits are.

In 2019 the International Scientific Association for Probiotics and Prebiotics set out a definition of a synergistic synbiotic: a combination in which the prebiotic is chosen specifically to be used by the live cultures it is packaged with, rather than to work on its own.

Under that definition the components do not individually have to meet their standalone thresholds. A sub-threshold prebiotic can be legitimate if it is feeding the organisms in the same capsule. On its face that describes exactly what we have built.

But the definition carries a condition, and the condition is the whole point of it. A synergistic synbiotic has to be tested as a finished product and shown to produce a health benefit. It is not a label you may apply because the components look complementary. It is a claim about a specific combination, demonstrated on that combination.

Femme Flora has not been tested as a finished product. So we include XOS as the fibre that sits beside the cultures, on the reasoning above, and we do not call the product a synbiotic.

We kept it, at 250mg. Before manufacture we weighed three options: remove it, keep it at the amount the capsule allows, or test the finished product first. We kept it, because it is the fibre the cultures are paired with in the formula, and because the alternative was dropping it for an amount the capsule could never hold.

What that means in practice: we list it as an ingredient, at its exact amount, and we make no claim for it on its own. As with Belle Balance, each batch’s certificate of analysis will be published on our verify page.

• Source: plant-derived, extracted from corncob. Confirmed by our manufacturer.
• Vegan: yes. Confirmed by our manufacturer. Unlike GOS, which is produced from lactose and is therefore usually not vegan — one of the reasons we chose XOS.
• FOS content: none. We asked for FOS to be removed and our manufacturer confirmed that none is blended into the raw material.
• Novel food status: XOS is an authorised novel food in Great Britain. That authorisation is specific — it covers XOS produced from corncob using a particular enzyme. The corncob source is confirmed. Our manufacturer has also confirmed the enzyme route in writing: xylanase from non-GM Trichoderma reesei, purified to more than 95% XOS.
• Label name: the authorisation also fixes how it must be written on the pack. It appears as Xylo-Oligosaccharides, in that exact form.

• XOS has no authorised health claim in Great Britain. We make none.
• We do not use the word "prebiotic" as a benefit. In UK law it functions as a health claim in its own right, and separately we could not support it at this dose even if it did not.
• We do not claim our 250mg feeds your gut bacteria, supports your microbiome, or does anything else. It is below the intake at which such effects have been demonstrated.
• We do not call this product a synbiotic, synergistic or otherwise, because we have not done the testing that word requires.
• We do not claim this product treats, prevents or reduces the risk of anything.

What we claim is the composition: 250mg of xylo-oligosaccharides from corncob per daily serving — listed at its exact amount, with no standalone claim.