The Key Ingredient You Need For A Healthy Gut

Research shows that about 70 per cent of people don’t eat enough vegetables, and almost 50 per cent don’t eat enough fruit. Apart from all the nutrients they’re missing out on, there’s the other issue of fibre.

If you’re feeling bloated or constipated and sluggish, you need to look at the amount of fibre in your diet. If you don’t have enough fibre in your diet, and most people don’t, it can contribute to constipation, IBS, bowel cancer, cardiovascular disease, haemorrhoids and diverticulitis. Fibre also stabilises blood glucose levels and helps reduce cholesterol levels.

Diets high in fruit or legume fibre are associated with greater microbial diversity. Short-term ‘fad’ diets, particularly exclusively animal-based ‘weight-loss’ diets that are high in protein, and low in fermentable carbohydrate and fibre, can also alter the balance of gut flora. Long-term adherence to these diets is likely to increase the risk of colonic disease, including colon cancer.

Types of fibre

There are three types of fibre: soluble fibre, insoluble fibre and resistant starch. Most whole foods contain some of each but are usually richer in one type than the other.

Soluble fibre

Soluble fibre pulls in water and dissolves to form a gel in the gut, softening stools and making it easier for them to pass through. It also slows the emptying of food from the stomach, which helps you feel fuller for longer. Most fibre supplements contain mostly soluble fibre.

Sources include fruit, vegetables, oats and oat bran, barley, psyllium husks, and dried beans and lentils including peas and soy products.

Insoluble fibre

Insoluble fibre is the indigestible hard outer skins of plant foods that act as a natural laxative and add bulk to stools, speeding up the transit of foods through the gut and preventing constipation.

Sources include wholegrain foods such as wholegrain bread and brown rice, the outer skins of fruit and vegetables, nuts and seeds, lentils, kidney beans, chickpeas, wheat bran, corn bran and rice bran.

Fibre potatoes tomatoes vegetables

Resistant starch

Resistant starch is, as its name suggests, the starch from food that resists digestion and absorption in the small intestine. This undigested starch then moves on to the large bowel, where the resident bacteria there break down and ferment these resistant starches. This process is important, as it creates short-chain fatty acids (SCFA) that have important benefits for gut health.

There are four different categories of resistant starch:

  1. Hard cell walls that humans are physically unable to digest, such as in grains
  2. Native starch granules that are protected from digestion by their physical structure, such as corn starch
  3. Retrograde starch, which develops when a starchy food, such as potatoes or pasta, is cooled
  4. Chemically developed resistant starch, most often found in packaged specialised

Why resistant starch is good for you

Resistant starch has been shown to have many benefits for digestive health, including:

  • bulking stools, which helps with bowel regularity
  • acting as a prebiotic, encouraging the growth of healthy bacteria in the gut
  • helping to regulate the pH of the bowels and reduce the production of potentially harmful by-products
  • protecting the mucous layer and cells of the colon
  • helping to produce SCFAs such as butyrate in the bowel, which are good for gut health.

It’s well documented that the SCFA butyrate, which is produced by resistant starch in the bowel, has some powerful benefits for gut health. Butyrate has been shown to help with fluid absorption in the intestines, reduce oxidative stress and inflammation in the bowel, and reinforce the intestinal defence barrier. It may also help control bowel motility, the contraction of muscles along the digestive system that moves food through the intestines.

Sources of resistant starch

The best sources of resistant starch are:

  • bananas (the less ripe they are, the more resistant starch they contain)
  • grains, such as raw oats
  • legumes (beans, peas and lentils)
  • potato, particularly cooked and cooled (as in potato salad)
  • pasta and noodles, particularly cooked and cooled (as in pasta salad)
  • rice
  • cashew

You may notice that a number of foods rich in resistant starch are also high-FODMAP foods. This is why it’s advisable to only follow the low-FODMAP diet for the recommended six to eight weeks. It’s incredibly important for gut health to include in your diet as much resistant starch as you can tolerate.

Your fibre needs

Women need about 25 g and men 30 g of fibre per day, but this isn’t always easy to achieve. Here’s an example of how you can meet your fibre requirements:

½ cup rolled oats = 5.7 g fibre

2 slices wholegrain bread = 6 g fibre

1 medium apple with the skin = 3.5 g fibre 30 g mixed nuts = 3 g fibre

½ cup cooked lentils = 3.7 g fibre 1 cup of strawberries = 3.8 g fibre

1 cup cooked brown rice = 2.6 g fibre Total = 25.3 g fibre

If you have a low-fibre diet and decide to switch to a high- fibre diet suddenly, you could experience flatulence and abdominal cramps. Introduce dietary fibre gradually by increasing the amount of fruit and vegetables and other wholefoods into your diet slowly over several weeks.

Frequently asked questions about fibre

Can you eat too much fibre?

Although most people don’t get enough fibre, many people over-compensate if they become constipated and have too much too quickly, which often makes their constipation worse or exacerbates the symptoms of IBS. If you need to increase your fibre intake, bear in mind that adding it too quickly can cause bloating, gas and gut pains. Add fibre slowly and gradually, and make sure you drink plenty of water.

What should I do about fibre if I have IBS?

IBS needs a low-FODMAP diet, which can typically remove some of your most precious fibre sources. While following the low- FODMAP diet, however, you can still meet your fibre requirements by eating wholegrains such as brown rice, rice bran and oats, fruits such as berries and kiwi fruit, vegetables such as carrot and cabbage, and most nuts and seeds.

Which foods are the best sources of fibre?

Fibre is found only in plant-based foods. Particularly good sources include legumes, pears, avocados, berries, stone fruit, dried fruit, bran and bran flakes, barley and other wholegrains, green and cruciferous vegetables (e.g. cauliflower, broccoli, brussels sprouts), nuts and seeds.

How do I increase fibre if I’m gluten-free?

All the high-fibre foods listed above except wheat, barley, rye and triticale grains are excellent sources of fibre on a gluten-free diet. Many gluten-free grains are also good sources of fibre, such as amaranth, brown rice, buckwheat, quinoa and sorghum.

What do I do if I’ve increased fibre but I’m still constipated?

It’s important to drink plenty of fluids (six to eight glasses a day) and make sure you get regular exercise. If you still have a problem, your doctor may need to arrange an assessment of your gut flora.

Extract from The Mystery Gut by Prof Kerryn Phelps AM, Dr Claudia Lee & Jaime Rose Chambers, published by Macmillan, available now.