Fibre Supplements: Why They Work for IBS-D and Bloating

The success of fibre supplements for IBS - Diarrhoea (IBS-D) and associated bloating relies on choosing low-FODMAP soluble fibre (such as psyllium husk or Partially Hydrolysed Guar Gum, PHGG), based on guidelines from experts like Monash University.

1. The Anti-Diarrhoea and Firming Action (Viscosity). The primary reason these fibres firm stools is their viscous (gel-forming) nature.

* Gelling Action: Soluble fibre dissolves in water and creates a thick, soothing gel in the gut, think toothpaste consistency.

* Water Absorption: This gel absorbs excess fluid common in IBS-D, adding bulk and structure to the stool.

* Slowing Transit: By bulking the stool, it slows down the fast transit time, allowing the colon to absorb the correct amount of water, which results in a firmer, normalised stool consistency.

2. Reduced Bloating and Prebiotic Effect (Slow Fermentation).

The fear that fibre worsens diarrhea or bloating is usually valid, but only for highly fermentable (High-FODMAP) prebiotics or irritating insoluble fibres (like wheat bran). The correct fibres reduce bloating due to their minimal fermentation.

Recommended Soluble Fibre (Psyllium, PHGG). Slow/Minimal | Low gas production, reduces bloating.

Avoided Prebiotics (Inulin, FOS) Rapid/High fermentation. High gas production, causes painful bloating

* Minimised Gas: Unlike high-FODMAP prebiotics, low-FODMAP soluble fibres are broken down very slowly, resulting in a low volume of gas production. This prevents the rapid, painful distension that triggers symptoms in a sensitive IBS gut.

* SCFA Production: The slow fermentation still allows for the production of Short-Chain Fatty Acids (SCFAs). These SCFAs nourish the colon cells, which helps maintain overall gut function and motility regulation, supporting the long-term stabilisation of stool and a healthier gut environment.

🌬️ Why Bloating Persists on the Low-FODMAP Diet.

While the Low-FODMAP Diet is highly effective for many, it's common for some individuals to still experience significant bloating and other symptoms during the initial Restriction Phase. This can happen for several reasons:

* FODMAP Stacking: This is the most frequent cause. Even "low-FODMAP" foods contain small amounts of FODMAPs. If someone eats many servings of different low-FODMAP foods in one meal (e.g., small amounts of onion, plus a restricted amount of mushrooms, plus a small amount of sweet potato), the total FODMAP load can exceed the personal tolerance threshold, leading to bloating.

* Non-FODMAP Triggers: The Low-FODMAP Diet addresses fermentation, but bloating can be caused by other non-FODMAP triggers, including:

   * Fatty/Large Meals: High-fat meals can slow digestion and increase the feeling of fullness and distension.

   * Carbonated Drinks/Air Swallowing: Swallowing air while eating too quickly, talking, or chewing gum can introduce gas into the digestive tract.

   * Underlying Conditions: Bloating may be caused by other issues not managed by diet, such as Small Intestinal Bacterial Overgrowth (SIBO), Celiac Disease (if undiagnosed), or problems with stomach emptying.

* Gut Healing Time: The gut takes time to recover. Even with the reduction in FODMAPs, existing inflammation, changes in gut motility, or a damaged intestinal lining might take several weeks or months to stabilise completely, meaning symptoms may not disappear instantly.

Here are the best UK-validated product tips for increasing low-FODMAP soluble fibre, focusing on widely available supermarket items:

🛒 UK Supermarket Tips for Soluble Fibre

1. The Supplement Aisle: Psyllium Husk

The most potent and best-studied soluble fibre for IBS is Psyllium Husk.

• Product to Look For: Most major UK supermarkets (Tesco, Sainsbury’s, Asda, Holland & Barrett) sell own-brand Psyllium Husk Powder or Whole Psyllium Husks. Look for it in the baking or supplements aisle.

• The Go-To Option: You can also find Fybogel (in sachets or tubs) in all UK pharmacies and large supermarket health sections. Fybogel's active ingredient is Ispaghula Husk, which is the generic name for psyllium. It is a highly viscous, low-fermentable soluble fibre, making it excellent for firming stools and gently regulating the gut.

• Tip: Start with a very small dose (e.g., half a sachet or half a teaspoon) mixed with plenty of water, and increase slowly to avoid initial gas or bloating.

2. The Low-FODMAP Certified Choice: PHGG

Partially Hydrolysed Guar Gum (PHGG) is another excellent, low-fermentable soluble fibre. It has the benefit of dissolving completely without thickening, unlike psyllium.

• Product to Look For: While not usually stocked on standard supermarket shelves, brands like Regular Girl or Sunfiber, or Biomel low FODMAP + fibre, can be found online or occasionally in UK health food stores, and are an excellent option for those who find psyllium too "gloopy."

• Tip: Because PHGG is tasteless and won't thicken, it can easily be stirred into a morning cup of tea, water, or a low-FODMAP smoothie.

3. Kitchen Staples for Soluble Fiber (Food-Based)

You can significantly increase soluble fiber using everyday supermarket food items that are low in fermentable FODMAPs (based on Monash guidance):

Food Item

Supermarket Tip

How to Use for IBS-D

Oats

Look for plain rolled oats or porridge oats (e.g., Quaker, own-brand).

Make porridge (using lactose-free milk or water) or low-FODMAP overnight oats. Start with a small portion (e.g., 40g) and increase gradually if desired

Linseeds (Flaxseeds)

Look for whole golden linseeds in the baking or free-from aisle.

IMPORTANT: To release the soluble fibre, the seeds must be ground. Add one tablespoon of ground linseeds to cereal, yoghurt, or smoothies, you can buy them ground in most UK supermarkets. They have demonstrated benefits in IBS.

Chia Seeds

Available in most baking/health food aisles (e.g., The Chia Co, own-brand).

Use up to 2 tablespoons as a low-FODMAP serving. Make chia seed pudding with lactose-free milk, or sprinkle over oats. Their gelling properties help firm stool.

Low FODMAP Vegetables

Carrots, Parsnips, Potatoes (peeled), Swede, Pumpkin, and Green Beans are excellent sources of soluble fibre.

Cooked is better! Cooking vegetables softens the fibres, making them easier to digest and less likely to cause irritation than raw veg.

low FODMAP Fruit

Ripe Bananas, Oranges, Strawberries, and Raspberries (within Monash serving sizes).

Ripe bananas are a fantastic soluble fibre source. Eat them whole or blend them into a shake. Stick to the Monash serving sizes for berries to avoid FODMAP stacking.

Short Summary

For IBS-D, the type of fibre you choose makes all the difference. Low-FODMAP soluble fibres like psyllium husk or PHGG are the most effective because they form a gentle gel in the gut, helping to firm stools, slow transit, and reduce urgency. Unlike highly fermentable fibres (such as inulin or FOS), these options ferment slowly, meaning minimal gas and less bloating while still supporting a healthy gut through SCFA production.

It’s also common for bloating to persist during the Low-FODMAP diet. This can happen due to FODMAP stacking, larger or higher-fat meals, swallowed air, carbonated drinks, or underlying conditions like SIBO or coeliac disease. In many cases, the gut simply needs time to heal.

For practical UK options, psyllium (such as Fybogel) is widely available in supermarkets and pharmacies, while PHGG products like Regular Girl or Sunfiber can be bought online.

Everyday foods such as oats, ground linseeds, chia seeds, cooked low-FODMAP vegetables, and ripe bananas can also help increase soluble fibre safely.

It’s also essential to increase fluid intake when adding fibre, as water helps the fibre form a soothing gel and prevents digestive discomfort.

If you're unsure which fibres, foods or strategies are right for your IBS symptoms, I offer 1:1 consultations to guide you step-by-step, personalise your approach, and help you feel calmer and more confident with your gut.

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