The Importance Of Fibre: Eating For Mental Wellness & Immunity

Fibre, at its core, is profoundly unglamorous— it’s something associated with the constipated, with the elderly, and the chronically ill.

However, this humble nutrient goes far beyond its ability to help with constipation. There are many health benefits associated with a high-fibre diet, including a higher immunity, maintaining a healthy weight, better mental health, as well as a lower risk of diabetes, heart disease, and some types of cancer.

Read on to learn more about why fibre is so much more than you thought it was, and how you can better incorporate it into your diet for a healthier gut, body and mind.

What is fibre, and why should you care?

Dietary fibre, also known as roughage, is a component of the plant cell structure, and hence naturally exists solely in plants. Nutritionally, fibre is a carbohydrate – a complex one. However, it doesn’t digest or behave the same way as sugar or starch, which we can digest efficiently and which contribute to our caloric intake and blood sugar.

Instead, it passes relatively intact through your stomach, small intestine and colon and out of your body. Do not be fooled though, it is far from the passive passenger most of us believe it to be. 

Fibre, even if we don’t fully digest it, not only has beneficial effects on our cholesterol and blood sugar, but can work some real magic with fermentation by our gut ecosystem.

There are in fact many types of fibre, but they are classified broadly into soluble and insoluble fibre. Most plants contain some combination of the two, but in different proportions.


1. Regulating bowels

Stating the obvious first: as mentioned, it’s no secret that fibre helps us maintain a regular bathroom schedule –
it does this by

  • Contributing to stool bulk, giving your intestines something to grip onto as they move things along
  • Absorbing and holding onto some fluid, to maintain viscosity of the stools

2. Strengthens immune system

Remember earlier when we said fermentation is where the true magic happens? This is it.

When fibre reaches the gut, it gets fermented by the gut microbiome into short-chain fatty acids (SCFAs).  There are 3 main types of these, and are produced in different proportions depending on the individual’s variety of fibre intake and unique microbiome. However they all work together and have significant effects on: 

  • Modulating differentiation and movement of immune cells
  • Cytokine production, among other anti-inflammatory functions
  • Maintaining healthy intestinal and organ walls to prevent infiltration (such as “leakage” of gut bacteria into surrounding tissues where they can cause infections)
  • Anti-proliferative effect on cancer/ tumour cells (note: this is useful for lowering long-term cancer risk, and not a reason to forgo treatment if one already has cancer)

3. Mental Health

The gut microbiome is known in scientific circles as “the Second Brain”, and for good reason. While the specific mechanisms are still being investigated, it is now well established that the gut directly influences brain health, development and activity through:

  • The vagus nerve (the major nerve connection digestive system and brain)
  • Modulation of the immune system
  • Synthesising certain neurotransmitters
  • Producing SCFAs, which reduce acute inflammatory responses in the nervous system and maintain healthy intestinal walls (preventing bacterial products from “escaping” and impacting the blood-brain barrier)


    To maintain a good balance in your microbiome, look no further than a high fibre diet! Different types of fibre serve as food for different micro-organisms too, so be sure to incorporate as many different plant foods as possible – this ensures that the entire ecosystem stays well-fed.

    If you need further convincing, it might be worthwhile to note that gut imbalances have been observed to produce more neuro-inflammation. While no direct cause and effect has been proven, imbalances are also well-documented in people with mental conditions such as depression, autism, Alzheimer’s and Parkinson’s, some of whom also exhibit altered inflammatory responses.

4. Lowers cholesterol levels

Did you know cholesterol is actually used in digestion? It is a component of bile, which helps us emulsify
(break down) fat for digestion. Usually, cholesterol is reabsorbed in the intestine after it does its job here. However as we know, many of us struggle with high cholesterol levels – wouldn’t it be convenient just to not reabsorb the cholesterol? Turns out, fibre is useful in this regard as well. 

By absorbing bile while passing through the intestines, holding onto it so that the body can’t reabsorb the cholesterol. With adequate fibre intake, we can excrete enough cholesterol to lower our blood levels by up to 10-15%. Now that’s handy!

5. Helps regulate blood sugar levels

Heard of “Low GI” foods/ diets? You will be glad to know that instead of spending 2-3 times more for such foods (you’re actually just paying for their advertising), you can simply add fibre to a meal or snack to lower the GI (Glycaemic Index). 

First, some clarification: GI is not an indicator of whether a food has sugar/ carbs or not. Far too many people misunderstand that “Low GI” means “Low sugar/ No sugar”, or “Low carb/ No carb”. 


GI reflects how quickly a certain food raises your blood sugar (by being digested and absorbed). While it is easy to demonise white rice for being high GI, many don’t stop to think how often they eat white rice on its own (probably never). 

The good news? Adding a generous dose of fibre will bring down the GI of the entire meal significantly – simply because fibre is so difficult to digest, that your body has to work a lot longer at extracting the carbs from the meal. This is actually the main reason we’re advised to eat brown rice instead of white rice- they’re actually the same plant, just that one version has more fibre!

How can I increase my fibre intake?

Hopefully we have convinced you of the magic of fibre – but are you eating enough? How do you know? 

In Singapore, the recommendation is 20g per day for women and 26g for men. Before getting down to details of counting grammes and reading food labels, try to keep as close to the Health Promotion Board’s Healthy Plate model as possible! 

Sticking to these proportions at each meal will take you close to the recommended fibre intake. 

Some tips: 

  1. Change up your variety of fruit and vegetables – there is no “best fruit” or “best vegetable”.
  2. Even with adequate fruit and veggies, most people will need to include wholegrains to meet their fibre requirements.
  3. Getting fibre from whole foods is always better than supplements.
  4. Choose whole foods over processed as fibre is usually removed during processing (e.g. whole fruit vs fruit juice) 
  5. Ensure adequate hydration! Too little fluid with too much fibre can cause constipation.

Stay tuned for our next edition where we expound more on ways to add fibre even when life gets in the way!

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