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Fiber & Your Gut

Today, I’m talking about the F word.


What is fiber?

Good question. Fiber is a type of carbohydrate found in plant foods that we don’t fully digest. It’s found in the skins, pips, flesh and shells of wholegrain cereals, fruits, vegetables, nuts, seeds and pulses (aka peas, beans and lentils). Your grandma might have called it roughage.

There are over a hundred types of fiber, and there are three traits that define each type:

  1. SOLUBLE or INSOLUBLE (does it dissolve in water?)

*note: this is how fiber is categorized by government guidelines and on food labels etc., so you hear about it most. This is the trait I’ll elaborate on below.

  1. VISCOUS or NON-VISCOUS (does it thicken?)

  1. FERMENTABLE or NON-FERMENTABLE (is it digested by our gut bacteria in a process that produces gas?)

Insoluble fiber does not dissolve and works like a broom, sweeping waste through our digestive system, adding bulk to our poo.

Soluble fiber dissolves in the digestive system, becoming gummy. It helps soften our poo and may regulate cholesterol levels.

Most foods contain a mix of both soluble and insoluble fiber, but some foods contain significantly more of one type. All fibrous foods provide a benefit, and we need both types.

Why is fiber good for gut health?

Eating enough fiber from a variety of high-fiber foods is most important (and will help you poo regularly). Experts also think high fiber diets protect against bowel cancer, because they lessen the amount of time harmful waste products stay in contact with the lining of our bowel.

But fiber has other important benefits too – like feeding your gut bacteria. The fermentable types of fiber aren’t digested or absorbed in the small intestine, and pass to the large intestine where they provide energy for the helpful bacteria that live there. The bacteria feast on fiber, turning it into beneficial compounds that have anti-inflammatory effects. These compounds help to keep our digestive system healthy.

Studies show eating a fiber rich diet can boost the numbers of helpful bacteria in the gut, whereas not getting enough fiber can have the opposite effect, leading to a less diverse microbiome. This means eating a fiber-rich diet is one step you can take to maintaining a healthy gut.

How much fiber should I eat?

I recommend that adults (16+) aim for 35-50 grams of fiber a day. Most of us don’t get anywhere near that much.

An easy place to start is to keep a food diary for a couple of days and see where you can add more fiber – start with a change to your breakfast, then add your next swap a week later.

Another tip is to compare the fiber content of foods by checking the ‘per 100 grams’ information – a food is high in fiber if it contains 6 grams of fiber or more. See how your breakfast cereal compares, or if you could switch your bread to one with higher fiber content.

How can I add more fiber to my diet?

You can boost your fiber intake by…

  • Getting five or more servings of fruit and veggies a day

  • Adding berries or sliced fruit and seeds to cereal

  • Choosing oats for breakfast

  • Eating veggies and potatoes with their skins on

  • Stirring linseeds into yogurt

  • Choosing wholemeal, wholegrain or rye bread over white bread

  • Swapping to wholemeal or lentil pasta instead of choosing white pasta

  • Adding frozen vegetables to pasta sauce

  • Adding lentils or beans to salads, soups, stews

  • Snacking on dried fruit, seeds and nuts

What about if I have IBS or a bowel condition?

If you have IBS or a bowel condition like Crohn’s or colitis, eating lots of fiber (especially insoluble fiber from wholegrain cereals, and breads, seeds and skins) isn’t helpful, as it can make symptoms like gas, bloating and diarrhea worse, and can aggravate bowel conditions.

TOP TIP: Take it slowly, and drink plenty of water too

If you are increasing your fiber intake, do so slowly over the space of a few weeks and make sure you drink plenty of water to give your digestive system time to adjust. Without water, fiber can’t do its job properly. Eating lots more fiber without giving your digestive system time to adjust can give you tummy aches and gas.

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