OptiFibre Alternatives: PHGG and Fibre Supplements Compared

If you are looking for an alternative to OptiFibre, you are usually after the ingredient behind it, not the brand. OptiFibre is 100% PHGG (partially hydrolysed guar gum) and is classified as a food for special medical purposes.¹² That exact fibre is also sold as an ordinary food supplement, often without a pharmacy and at a lower price per gram.

This matters because the NHS recommends 30 g of fibre per day, and most adults fall well short of it.³ In this guide we explain what PHGG is, why OptiFibre is classified differently from most powders on the shelf, and when PHGG, psyllium or inulin is the better choice. For specific product picks you can buy, see our overview of the best fibre supplements in the UK. For the bigger picture of how fibre fits into GLP-1 treatment, read our complete guide to fibre and GLP-1 medications.

What is PHGG?

PHGG, partially hydrolysed guar gum, is a soluble, low-viscosity fibre made from the guar bean. It dissolves completely and clear in liquid, is tasteless, and does not change the texture of drinks or food. In the colon, gut bacteria ferment PHGG slowly into short-chain fatty acids. That slow fermentation is why PHGG causes far less gas and bloating than fast-fermenting fibres such as inulin or FOS. PHGG is also considered low FODMAP. The best-known branded PHGG raw material is called Sunfiber.

What is OptiFibre, and what is it made of?

OptiFibre is a product from Nestlé Health Science. Its only active ingredient is PHGG, meaning 100% partially hydrolysed guar gum, gluten-free and plant-based.¹ One level scoop is 5 g, stirred into 200 ml of liquid or 150 g of food. The manufacturer advises building the dose up gradually (1 scoop on the first three days, 2 scoops from day four) and using the product under medical supervision for at least 14 days.¹

The decisive point is the legal classification: OptiFibre is a food for special medical purposes and is sold through pharmacies in the UK. What that means is the subject of the next section.

FSMP or food supplement: where is the difference?

This is the real heart of the question about an alternative. The same fibre can be sold in two different legal categories.

A food for special medical purposes (FSMP) is, under Commission Delegated Regulation (EU) 2016/128, intended to feed patients with a diagnosed disease or disorder who cannot, or can only with difficulty, meet their nutritional needs through ordinary food. Such products are developed in cooperation with healthcare professionals and are meant to be used under medical supervision.² OptiFibre falls into this category.

A food supplement is, under Directive 2002/46/EC, a foodstuff that supplements the normal diet and supplies concentrated nutrients or other substances with a nutritional or physiological effect in dose form, such as capsules, powders or sachets.⁴ Most PHGG powders you buy online or in a chemist belong to this category.

In practice this means the legal classification determines the route to market (pharmacy with medical supervision versus general retail), the presentation, and often the price per gram, not the fibre itself. PHGG stays PHGG.

What alternatives to OptiFibre are there?

Two directions make sense.

Same ingredient, different category. If you want to stay with PHGG, you can find pure PHGG or Sunfiber powders sold as ordinary food supplements. They contain the same fibre as OptiFibre but are usually available through general retail. We name specific, vetted products for the UK market in our overview of the best fibre supplements.

Different fibre, depending on your goal. PHGG is not the best choice for every goal. For chronic constipation, psyllium husk has the broadest evidence; for a prebiotic effect, chicory inulin leads. The next section covers matching the type to the person.

PHGG, psyllium or inulin: which suits whom?

• PHGG is the most tolerable option. Tasteless, clear-dissolving, low FODMAP and low in gas. Good for sensitive digestion, IBS, or GLP-1 users who get nausea from other fibres.
• Psyllium husk has the broadest clinical evidence for chronic constipation. A 2022 meta-analysis in the American Journal of Clinical Nutrition found that fibre improves stool frequency, with significant effects above all for psyllium and pectin, and particularly at doses over 10 g per day for at least four weeks.⁵ Psyllium works mechanically and forms a gel.
• Chicory inulin is the only prebiotic fibre with a proprietary EU health claim for bowel function at 12 g per day. It ferments faster and can cause more gas at first.

If nausea or bloating is your main problem, PHGG is usually the best starting point. If constipation is the priority, psyllium husk is the strongest-evidence choice.

How do you dose PHGG?

A typical effective dose is 5 to 10 g per day. As with any fermentable fibre, build up slowly. Start at a low dose and increase over one to two weeks to avoid bloating. PHGG stirs clear into water, coffee or food. If you take a GLP-1 medication, separate your fibre from the medication in time.

What does the evidence say about PHGG?

PHGG is well tolerated and supported by several controlled trials, even if the evidence base is narrower than for psyllium. In a randomised, single-blind, placebo-controlled trial in care-home residents, 5 g of PHGG daily for four weeks led to significantly less laxative use than placebo.⁶ In irritable bowel syndrome, a randomised trial showed benefits of PHGG over placebo for both the constipation-predominant and diarrhoea-predominant types.⁷ The effect on stool frequency alone varies by study population. The most consistent advantage of PHGG is its very good tolerability with low gas production.

Which is the right choice?

The search for an alternative to OptiFibre almost always leads back to PHGG, the active ingredient in OptiFibre itself. As a food supplement, the same fibre is often available without a pharmacy and at a lower price per gram. If your goal is maximum tolerability, PHGG is a good choice. If constipation is front of mind, psyllium husk has stronger evidence; for prebiotic effects, chicory inulin. For specific products you can buy in the UK, see our guide to the best fibre supplements.

Frequently asked questions

Is OptiFibre the same as PHGG? Essentially yes. OptiFibre from Nestlé Health Science is 100% PHGG. The difference from many alternatives is not the fibre but the legal classification as a food for special medical purposes.

Is there a cheaper alternative to OptiFibre? Pure PHGG or Sunfiber powders are also sold as ordinary food supplements. They contain the same fibre as OptiFibre but are usually available through general retail without a pharmacy.

PHGG or psyllium husk for constipation? Psyllium husk has the broadest clinical evidence for chronic constipation. PHGG is the gentler option with less gas, and it suits sensitive digestion, IBS, or nausea on GLP-1 medications.

How much PHGG should you take per day? A typical effective dose is 5 to 10 g per day, built up slowly over one to two weeks.

Is PHGG low FODMAP? Yes. PHGG is considered low FODMAP and produces far less gas than faster-fermenting fibres such as inulin or FOS because it ferments slowly.