What is dietary fibre?

Dietary fibre, also known as roughage is a term used for carbohydrates found naturally in plants. It is important for gut health and the normal functioning of the gut. Research shows that eating a high-fibre diet can help balance gut microbiota (the term given to the collection of bacteria living in our intestine) by increasing the useful strains and reducing the harmful ones. The good bacteria support the immune system against inflammatory disorders and allergies. It also reduces the risk of metabolic syndrome which is a combination of factors that increases the risk of developing coronary heart disease and diabetes. Let’s explain everything you need to know about fibre and how to increase your dietary fibre intake.

📝 How do humans digest carbohydrates?

Most carbohydrates eaten are broken down into sugar molecules called glucose. Fibre however is a type of carbohydrate that the body can’t digest. It passes through the body undigested after going through the whole digestive system. Fibre plays a role in regulating the body’s use of sugars, helping to keep hunger and blood sugar in check.

Dietary fibre is the part of plants that you eat but which doesn’t get digested in your small intestine. Instead, it is completely or partially broken down (fermented) by bacteria in your large intestine. The fermentation process feeds the good bacteria resulting in positive health effects.

🥬 Why do I need fibre in my diet?

Fibre helps to keep our digestive system healthy, move food through the gut, and maintain a healthy body weight. Fibre adds bulk to stools by absorbing water. This makes stools softer allowing them to move more quickly through the gut, making them easier to pass. Eating enough fibre can help keep things working in the digestive system and encourage bowel movements. Along with drinking plenty of fluids and keeping active, ensure you have plenty of fibre in your diet.

💧 The importance of water

The importance of water can not be underestimated when trying to increase the amount of fibre you consume. If you eat more fibre but don’t drink more water, your stools can become too dry, causing or worsening constipation. To avoid this make sure to drink plenty of fluids.

On the other hand, if you have diarrhoea, you might be tempted to drink less water to reduce the looseness of your stools, but persistent diarrhoea puts you at risk of dehydration. If you are losing a lot of liquid through diarrhoea, an electrolyte drink might be more suitable than plain water.

🍏 Are there different types of fibre?

Soluble fibre

As the name suggests this type of fibre dissolves easily in water and comes from the inside of plants. It is broken down in the large intestine into a gel-like substance and can help to reduce blood cholesterol. This is found in foods such as chickpeas and carrots.

The main types of soluble fibre include pectins (in vegetables, and fruits), gums (gum Arabic), mucilages (guar, carrageenan), beta-glucans (in oats, barley, and mushrooms), oligosaccharides and some hemicelluloses.

Insoluble fibre

As the name suggests this type of fibre does not dissolve in water and comes from the outer part of plants. It moves through the digestive tract absorbing fluid and picking up other waste matter. The fibre aids the journey of the waste matter through the intestines and out the other end. This type of fibre helps to prevent constipation and is found in foods such as rice, nuts and seeds.

The main types of insoluble fibre include cellulose (which makes up the majority of plant cell walls), many hemicelluloses (cereal fibres), and lignins (non-starch polysaccharides).

Resistant starch

This is a soluble fibre that is highly fermentable in the gut. It gets broken down by good bacteria to produce short-chain fatty acids which are important to bowel health and may protect against cancer. When the bacteria ferment, fibre gases are also produced which can cause wind and stomach discomfort in some people. Bananas, potatoes, grains and pulses contain resistant starch.

📝 What is the recommended daily intake of dietary fibre for adults?

The NHS guidelines say we should increase our fibre intake to 30g a day as part of a healthy, balanced diet. As most adults eat an average of about 20g a day, we need to find ways of increasing our intake.

The Dietary Guidelines for Americans, 2020–2025 recommends that adults eat 22 to 34 grams of fiber each day (depending on your age and sex).

The European Food Safety Authority (EFSA) has set a recommended daily intake on dietary fibre of 25 g of dietary fibre for adults.

🏥 What are the health benefits of increasing fibre intake?

Reduced risk of type 2 diabetes

Chronic inflammation is a common underlying factor in many chronic diseases such as diabetes, obesity, and certain types of cancer. Reducing inflammation through a low-inflammatory diet such as a high-fibre diet has been shown to lower your risk of developing or improving blood sugar levels.

As mentioned earlier soluble fibre attracts water in the gut, forming a gel, which can slow digestion. This may help prevent blood glucose spikes after eating and reduce hunger.

Lower risk of heart disease

Studies have found that a high intake of dietary fibre can lower the risk of heart disease and death from cardiovascular disease. Soluble fibre may also lower blood cholesterol levels by interfering with bile acid production. Clinical studies also suggest lowering blood pressure with diets with high levels of fibre.

Reduced risk of colorectal cancer (colon and bowel cancer)

A meta-analysis of studies found fibre from fruits, vegetables, and legumes offer some protection from colorectal cancer. This could be because fibre helps food move more quickly through the gut and also because high-fibre diets can reduce the risk of obesity, which is linked with bowel and colon cancer.

Weight management

Chronic inflammation can contribute to weight gain and obesity. By adopting a low-inflammatory diet that focuses on whole, nutrient-dense foods, you can support healthy weight management and reduce the risk of obesity. High-fibre food tends to be low in calories and slows gastric emptying and transit time of food through the digestive system, which increases satiety and can prevent overeating.

Constipation & haemorrhoids

Fibre is generally recommended for treating constipation and haemorrhoids resulting from constipation. Consuming more insoluble fibre and plenty of water is enough to relieve symptoms for someone suffering from constipation. It’s the simplest, safest, and often most effective treatment for this common symptom. However, sometimes fibre is not enough for individuals with chronic constipation or constipation associated with irritable bowel syndrome and requires different treatment.

Enhanced immune function

Chronic inflammation can reduce immune function, making it harder for the body to fight off infections and diseases. Reducing inflammation through a high fibre, low-inflammatory diet can support a healthy immune system and enhance your body’s ability to defend against illness.

Reduced joint pain and arthritis symptoms

Inflammatory arthritis, such as rheumatoid arthritis, involves chronic inflammation in the joints. Following a low-inflammatory diet can help reduce joint pain, stiffness, and inflammation associated with arthritis, improving overall joint health and quality of life.

🥦 What does a high-fibre diet contain?

High-fibre food comes from plant foods, most of the best sources of fibre are:

Vegetables

• Lettuce, Swiss chard, raw carrots, and spinach
• Tender cooked vegetables, such as asparagus, beets, mushrooms, turnips, and pumpkin
• Baked potatoes and sweet potatoes with skin
• Broccoli, artichokes, squashes, and Brussel sprouts

Legumes and nuts

• Legumes, such as lentils, black beans, split peas, kidney beans, lima beans, and chickpeas
• Nuts and seeds, such as sunflower seeds, almonds, pistachios, and pecans

Fruits

• Apples and bananas
• Peaches and pears
• Prunes
• Strawberries
• Raspberries
• Blueberries
• Blackberries
• Avocados
• Kiwis

Grains

Grains are another important source of dietary fibre.

• Whole-grain breads
• Brown rice
• Quinoa
• Popcorn
• Wholegrain breakfast cereals, such as bran, shredded wheat, and puffed wheat (bran, oat bran or wheat bran)
• Whole-wheat pasta and rice
• Bran muffins

Ideally, you should eat a variety of fruits, vegetables, whole grains, and nuts because different types of fibre are found in different foods. High-fibre foods need to be added to your diet slowly to reduce gastrointestinal symptoms such as gas, bloating, and cramps.

❌ Foods that don’t contain fibre

Animal products and fats do not contain fibre. The following foods don’t contain any fibre or very little:

• Meat (beef, chicken, pork, lamb)
• Fish (salmon, tuna, prawns)
• Products made with white flour
• Oils and fats (butter, ghee, lard, olive oil, canola oil, coconut oil)
• Eggs
• Dairy products (milk, cheese, sour cream, yoghurt, etc.)
• Milk alternatives (soy milk, almond milk, rice milk, coconut milk )
• White bread
• White pasta
• White rice
• Fruit and vegetable juice without pulp

✔️ Simple food swaps and tips to increase fibre in the diet

When you read food labels, check for the grams of fibre per serving or 100g to check if it is a high-fibre food.

• Replace white bread with whole-grain bread
• Replace white pasta with wholewheat pasta
• Add vegetables to every meal
• Eat the skin of fruits and vegetables (if they are safe to eat), since most of the fibre is often found there
• Swap mayonnaise or cheese for avocado in sandwiches, salads or dips
• Remember to sprinkle nuts or seeds on your salad
• Replace meat for beans or lentils in recipes
• Swap fruit juices for whole fruits and vegetables
• Top yoghurts, cereal and oatmeal with frozen, fresh or dried fruit
• Snack on vegetable sticks with hummus or guacamole, popcorn and fresh fruit
• Have a supply of frozen vegetables in your freezer
• Canned beans or chickpeas are a quick way to add fibre to a meal

💊 Fibre supplements

Getting fibre from fresh, whole foods is the preferred way but if you don’t get enough from your diet, fibre supplements can help. Supplements contain fibre that is extracted from their natural sources and then added to supplements, foods and drinks to boost their fibre content. They are available in a variety of forms such as powders, capsules, or gummies.

Some of the most common ingredients in fibre supplements are:

• Psyllium
• Inulin
• Calcium polycarbophil
• Flaxseed
• Methylcellulose
• Arabinoxylan

Too much inulin (30 grams) has been shown to cause a spike in body inflammation but also decreased inflammation in the body. This shows that people may respond differently to different fibre supplement ingredients and amounts. Always speak to a healthcare professional before taking supplements.

📝 Conclusion

There are many health benefits provided by dietary fibre. It keeps your digestive system in check, fights constipation and helps with weight loss. Additionally fibre has been shown to reduce the risk of medical conditions such as heart disease and diabetes. A diet rich in fibre from fruits, vegetables and grains can help to achieve a healthy body.

Sources

• Carbohydrates and Health
• Are you eating enough fibre? – BHF
• Dietary Fibre – Gastrointestinal Society
• Dietary fiber: Essential for a healthy diet – Mayo Clinic
• How to get more fibre into your diet – NHS
• Dietary fibre in foods: a review – PMC
• Fiber – The Nutrition Source