Soluble Fibre, Insoluble Fibre, Functions And Where to Find It

June is Bowel Cancer Awareness Month which claims the lives of 103 Australians every week (5,375 people a year) – but it’s one of the most treatable types of cancer if found early[i]. As well as regular testing, diet is an important factor where it comes to prevention.

Many studies have shown a diet high in fibre can help reduce the risk of developing bowel cancer. This features focuses on fibre – which four out of five Australians don’t consume enough of – and the many benefits of fibre for all-round good health.

Dietary fibre refers to the parts of plant foods that aren’t digested. Although you can’t absorb it – it never leaves your gastrointestinal tract – fibre is vital for good health. Experts recommend around 30g of fibre recommended daily for adults.

Here are six reasons your body needs fibre and easy ways to add more fibre into your diet.

1.      It gives your large intestine a workout

Insoluble fibre (the outer shells of seeds, grains, fruits, and vegetables) can be stringy or coarse. The large intestine is a long muscular tube and, like all muscles, it needs exercise. Insoluble fibre draws water to it and softens the stool making waste more comfortable to pass. Keeping things moving helps to prevent conditions such as constipation, haemorrhoids and diverticular disease.

2.      It feeds your probiotic bacteria

Resistant starch, although not traditionally thought of as fibre, acts in a similar way. It resists digestion in the small intestine (where most food is digested) and when it enters the large intestine, provides food for gut bacteria. Healthy gut bacteria play a key role in controlling inflammation; too much chronic (long-term) inflammation may predispose people to type 2 diabetes.

Find resistant starch in legumes (peas, beans and lentils), seeds, grains, green bananas and certain cooked-and-cooled starchy foods including potatoes and rice.

3.      It helps you feel fuller for longer

Soluble fibre is usually soft and moist and is found in fruit (but not the skins), vegetables and pulses, oats and ground flax seeds. This type of fibre mixes with water in the gut forming a gel-like substance, helping to slow down digestion which, in turn, helps you feel fuller for longer. It also feeds your beneficial gut bacteria. Plus, the physical bulk helps you feel fuller so you may be less likely to consume excess calories.  

4.      It reduces the risk of type 2 diabetes

Research suggests that if every Australian adult added just 4–5g of fibre to their diet each day, it could help prevent 126,000 cases of type 2 diabetes and 64,000 cases of heart disease saving our economy $3.3 billion[ii].

Eating a diet that is rich in fibre can help to flatten the rise in blood glucose (sugar) after eating. And, because it can help to delay the absorption of glucose from the gut and into the bloodstream, your body does not have to release as much insulin to return blood glucose levels to normal.

Again, fibre provides food for your probiotic bacteria, and good gut bacteria can play a part in weight regulation since obesity is a significant risk factor in the development of type 2 diabetes.

Soluble fibre is especially important if you have insulin resistance or type 2 diabetes. Find it in psyllium husk, legumes, oats and ground flax seeds. Ripe fruit and vegetables naturally contain more soluble fibre.

5.      It protects your heart

A high-fibre diet may help protect your heart by reducing cholesterol levels in the blood – the gel-like substance may reduce glucose and cholesterol absorption into the bloodstream. Again, it can also help to control weight. High cholesterol levels, high blood glucose levels and being overweight are all risk factors for heart disease.

Fibre also increases the production of short-chain fatty acids by probiotic bacteria which have also been shown to help to reduce inflammation and cholesterol production.

6.      It’s linked with gut health

Higher intakes of fibre are associated with lower rates of bowel cancer. Probiotic bacteria the short-chain fatty acids produced help to keep the lining of the intestine healthy. They also help the body absorb minerals, enhance fat and glucose metabolism in the liver, and have anti-diarrhoeal and anti-inflammatory properties. Butyrate, one of the short-chain fatty acids that is produced by the fermentation of fibre in the large intestine, may reduce the risk of tumour growth.

What about supplements?

Fibre supplements may help people to enjoy the many health benefits of fibre, relieve constipation and maintain regularity. Plus, by choosing a diet that is low in saturated fat and by adding soluble fibre, such as psyllium husk, may help to lower blood cholesterol levels; this may help to reduce the of heart disease. It is important to obtain the advice of a healthcare practitioner especially if you have certain health conditions.

Be cautious

In some medical conditions, it may be important to restrict insoluble fibre. These include acute or subacute diverticulitis, acute phases of certain inflammatory bowel conditions such as ulcerative colitis or Crohn’s disease, and after some types of intestinal surgery.

Some types of fibre can exacerbate underlying irritable bowel syndrome (IBS). If you have IBS and you’re following a low-FODMAP diet, you may find some high-fibre foods make your symptoms worse. Talk to your healthcare practitioner for individual advice.

Go slow and drink plenty of fluids

If you’d like to consume more fibre, go slowly over a few weeks. Too much too soon can trigger discomfort and leave you feeling bloated and constipated. And make sure you drink plenty of fluids as fibre draws water into the bowel and needs fluid to work properly.

How to do it

Boost your fibre intake by choosing wholegrain foods most of the time, add legumes (beans, chickpeas and lentils) to salads, soups and stews at least two-to-three times a week, and try to choose high fibre cereals instead of fibre-stripped refined foods.

Aim for around 30g of fibre a day. Here are some good food sources of fibre.

Cereals and breads

Wholegrain barley wrap 1 wrap = 10g

Wholemeal pasta (cooked) 1 cup = 10g  

Soy-linseed bread 2 slices = 6g

Rolled oats 1/4 cup = 4g

Weet-Bix 2 biscuits = 3.5g                          

Brown rice (cooked) 1 cup = 3g   

Quinoa (cooked) 1/2 cup = 2.5g

Beans and pulses            

Baked beans 130g can = 6g

Four-bean mix 125g can = 6g

Chickpeas (cooked) 1/2 cup = 5g

Lentils (cooked) 1/2 cup = 3.5g

Hummus 2 tbs = 2.5g     

Veggies and fruits

Vegetables (cooked) 1 cup = 8g  

Carrot/celery sticks 1 cup = 4g

Banana 1 medium = 3g

Apple 1 medium = 3g     

Sweet potato 1/2 small = 3g

Avocado 1/4 medium = 2g

Potatoes 2 small = 1.5g

Dried fruit 2 tbs = 1.5g

Nuts and seeds

Chia seeds 1 tbs = 5.5g

Plain popcorn 2 cup = 4g              

Almonds 20 nuts = 3g

Peanut butter 1 tbs = 3g               

Seed mix 2tbs = 2.5g

References

1. https://www.letsbeatbowelcancer.com.au/events/bowel-cancer-awareness-month/

2. https://www2.deloitte.com/au/en/pages/economics/articles/expenditure-savings-increased-intake-grain-fibre-australia.html

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