Increase your intake of dietary fibre

This column is written by Stig Bengmark – professor emeritus, researcher, lecturer and author. Read more of Stig’s columns here.

Without fibre, our gut bacteria will disappear

Dietary fibre is the most important food for our gut bacteria. Without fibre, the intestines do not function properly, and many of the good bacteria species disappear and are replaced by bad bacteria that cause inflammation and disease. When we live an optimal, healthy lifestyle and eat foods that promote the growth of good bacteria, we have 800-1000 different types of beneficial bacteria in our gut (a total of about 100 trillion), which are fully engaged in the job of extracting the nutrients we need for optimal health from our food. In addition to bacteria, the gut is home to many other microorganisms whose role is not yet fully understood. Most dietary fibre cannot be digested by the enzymes we have in our stomachs and small intestines; this can only be done with the help of our “resident flora”, particularly in the large intestine. We therefore have two separate digestive systems, both of which need to be working optimally, and by carefully choosing a bacteria-friendly diet rich in a wide variety of dietary fibre and rich in plant antioxidants, we ensure that these systems work optimally. It is actually very unfortunate that people in the Western world today overlook the need to create the right conditions for good bacteria – for this, they end up paying a very high price in terms of increased inflammation in the body and the accompanying rapidly growing global tsunami of chronic disease and premature aging.

The gut – the body’s afterburner

Ideally, bowel transit time should be between 20-24 hours. About two hours after eating, dietary fibre reaches the large intestines where it is broken down in a reverse “assembly line” system. The bacteria have different and very specific functions that are localised in different “territories” – some functions are carried out right at the very beginning of the intestinal tract and others at varying distances from the anus. The bacteria that break down the types of fibre that are the most difficult to digest, e.g. cereal grains (especially rye), are closest to the anus. Many types of fibre cannot even be broken by our bacteria and pass through our bodies undigested – but they are still very important because they increase the volume of the material in the intestines and speed up the passage of intestinal contents. The process of digesting the fibre we eat takes almost 24 hours – a time during which lots of energy and other nutrients are continuously, gently and slowly extracted from our food and supplied to the body. The digestive action of the gut has been likened to the afterburner of a jet engine – it “squeezes out” as much energy as possible from the food.

A missionary doctor in Uganda put us on the right track

The first person to make us aware of the important role of dietary fibre was the missionary doctor Dennis Burkitt, who worked in Uganda 40-50 years ago. Burkitt had observed that Ugandan’s who lived in the bush avoided most of the diseases that plagued the rest of humanity, both locally in the gut (such as appendicitis, inflammatory bowel disease and cancer) but also generally in the body (such as heart disease and diabetes). In 1979, he released the book Don’t Forget Fibre in your Diet, which became an international bestseller and which awakened the world’s interest and understanding of the importance of dietary fibre.

Burkitt first thought that the explanation for this anomaly was the very large proportion of raw, completely unprocessed plants in the African diet, which accelerated passage through the gut and helped the body remove toxins more quickly. As time went on, he also realised the importance of all the nutrients that bacteria can supply to the body. Burkitt measured stool size and the rate of passage of food from the mouth to anus (this can be done, e.g., by eating blueberries or whole corn and noting how long it takes to come out). He found that the average stool size in Europe was about 60 grams/day – compared with ten times that in Uganda (about 600 grams/day) – and the average passage time was about 100 hours in Europe – compared with about 20 hours for people living in the African bush. At this point in time, other researchers had also observed that more than half of patients in long-term care in Europe had a passage time of more than 14 days.

Burkitt’s experience contributed a level of knowledge that was incredibly valuable to humanity and likely of greater significance than the contributions of any Nobel Prize winner. Burkitt was never awarded the Nobel Prize but did receive many other accolades and actually came close to receiving the Nobel Prize in another area – for the identification of a previously unknown type of tumour, which was named “Burkitt’s lymphoma” after him.

The counterparts to the Swedish National Food Agency in various Western countries have set the recommended intake of dietary fibre to 25-35 grams per day, which is really not enough. Our ancestors, much like the communities that still live the way our ancestors did, ate more than twice that amount – the Hunza people, for example, consume a 99% plant-based diet, much of it raw. And in reality, studies show that most Westerners do not consume even  half as much fibre as the health authorities recommend. When people choose to consume a diet like this, they are actually choosing to be sick when they have every opportunity to be healthy.

Buy fresh and raw plant-based foods, preferably locally produced and organic

It is the things that are done to your food by the food industry (and yourself) which, through unnecessary heating and cooking, destroys the precious, nutritious fibre our bodies so desperately need. In addition to this, valuable fibre turns into sugar as fruits like bananas, apples and pears ripen. Eating a fresh, raw diet is therefore an important principle for good health. A head of lettuce that is cut away from its roots loses half of its antioxidant content after just 30 minutes, and the process continues even if it is stored in the refrigerator. The logistics involved in getting fresh vegetables to the Swedish market has a lot of room for improvement; it takes far too long for vegetables to get to the shops and they sit on the counters far too long, compared with the UK, for example. Keep this in mind! For many vegetables, it is actually better to buy frozen – hopefully frozen quickly after harvest. The loss of fibre is not as bad as the loss of antioxidant content, but one thing is certain – vegetables also lose fibre during storage.

No way, you say – I can’t tolerate raw root vegetables and other raw vegetables. There is a solution for that too – cook them (preferably by steaming) – and let them cool before eating. It has actually been found that the fibre is re-formed when it cools – something known as retrogradation or recrystallization. When root vegetables are eaten cold, not as much sugar is absorbed in the small intestine; it instead reaches our friends, the good bacteria in the large intestine, to a large extent as fibre. The bacteria’s favourite food! It can be a good idea to cook enough root vegetables (including potatoes) to last for several days, then store them in the refrigerator and eat them cold. This is both a practical and nutritious solution – root vegetables are actually often tastier when they are cooked and chilled. If none of these suggestions work for you, there are endless options to get the fibre you need as a dietary supplement.

Some particularly healthy types of fibre that interest me

Fibre is found everywhere in nature, there are actually thousands of different varieties and they largely make up the “building blocks” for plants. Dietary fibre carries the antioxidants we need, which are released from the fibre by the gut bacteria. Most of the health properties of fibre are still unexplored – there are both beneficial as well as harmful types of fibre. Variety and moderation are important – you can actually get too much of certain types of fibre.

There are four types of fibre that have especially piqued my interest:

Pectin (E440)

Unripe, green bananas contain a considerable amount of pectin (1/3 of the fibre in the fruit is pectin) as do apples, citrus fruits (mostly in the peel), plums, cherries, grapes, cranberries, blueberries, gooseberries, quince, red and black currants. The pectin in these fruits forms a gel, which makes these fruits especially good for use in marmalades and jams. Some extra added pectin also reduces the need for added sugar, and if you freeze the marmalade/jam, hardly any sugar is needed at all. Pectin has been shown to have significant positive effects for a variety of diseases. It is the pectin’s ability to stick to high-moisture surfaces that gives it its unique ability to protect mucous membranes and deliver medications to exposed surfaces – from the nostrils to the anus. It was 25 years ago that we demonstrated in an experiment that green bananas were as effective as the best drug of the time, Astras Losec, in protecting against and healing gastric ulcers and protecting the oesophagus from inflammation caused by acid reflux. Unripe bananas are also excellent for quickly reducing diarrhoea and vomiting in people with gastrointestinal disease and are widely used in developing countries from 6 months of age and up.

Other known effects of pectin include:

* Dramatically lowers blood cholesterol.
* Thins the blood.
* Prevents diseases such as diabetes, arteriosclerosis and stroke. Experimental studies even suggest that infarct size is significantly reduced when pectin is administered.


Abundant in asparagus, Jerusalem artichokes, leeks, garlic, red onion and other members of the onion family (“a day without onions is a day lost” – eat raw or lightly steamed). Bananas have been shown to be especially good for inhibiting and protecting against the onset and recurrence of various inflammatory bowel diseases. But at the same time, inulin is unfortunately one of the types of fibre that creates the most flatulence, bloating and gurgling in the stomach. So even though inulin is beneficial, daily intake must be limited to a maximum of 3 g per day.


Abundant in brewer’s yeast, shiitake mushrooms, cereal grains and especially oats (which explains why oats are considered to be especially healthy in so many ways). You never have to worry about limiting the amount of oats you eat – I am inclined to say the more the better. There are a large number of significant health benefits linked to the consumption of more than 3 grams of beta-glucan per day:

* Helps protect the heart and blood vessels by significantly lowering both total cholesterol and bad cholesterol levels in the body.
* Lowers blood pressure.
* Protects against infection, especially bacterial infection.
* One substance found in shiitake mushrooms, lentinan, has been shown to protect against cancer and also contributes to lower growth rates of cancer that has already manifested.

Resistant starch

Abundant in green bananas, uncooked potatoes and other root vegetables, peas, beans, lentils, cereal grains and seeds. Unlike other starches, resistant starch cannot be absorbed in the small intestine (hence the name), but reaches large intestine intact, where the bacteria digests it releasing nutrients and other beneficial substances. Benefits:

* prevents diabetes by improving insulin sensitivity and insulin recovery
* reduces levels of both sugar and insulin in the body/blood
* increases the production of butyric acid, important nourishment for the intestinal walls
* butyric acid seals the intestinal mucosa and prevents leakage of toxins and bacteria into the body
* strengthens the immune system
* reduces the degree of inflammation

The bacteria celebrate, but your stomach and gut may protest

Many types of fibre must be consumed sparingly. Variety and moderation are key, and many types of fibre can be consumed in large quantities while others should be consumed in moderation, otherwise the gut will not be able to handle the fibre – you can end up with problems like gassiness, flatulence, swelling of the abdomen and often pain. If this condition is chronic, it is called “irritable bowel syndrome” (IBS), a condition that afflicts about one in every three Swedes. Australian scientists have conducted research and published a list called FODMAP, which lists sources of fibre you need to be careful with and sources of fibre you can eat plenty of. Fruits and vegetables that contain fibre and can irritate the gut to some degree are:

Fruits: Bananas, blueberries, grapefruit, grapes, canary melon, kiwis, lemons, limes, mandarins, oranges, passion fruit, pineapple, raspberry, cantaloupe, tomatoes
Vegetables: Alfalfa sprouts, bamboo shoots, bean sprouts, carrots, cabbage, garlic, aubergine, green beans, lettuce, chives, parsnips, potatoes, winter squash, radishes, spring onion (but only raw), squash, courgette
Cereal grains: The best are gluten-free products – oats, polenta, quinoa, rice, corn and spelt
Nuts: but always less than a handful per day of macadamia nuts, peanuts, pecans, pine nuts, pumpkin seeds, sesame seeds, sunflower seeds, walnuts.

Sugar is fibre that has been destroyed through processing – avoid processed sugar

The Stockholm Consumer Cooperative Society has compiled lists of breakfast foods that generally contain too much sugar. There are also probiotic drinks available on the market that contain far too much sugar. If you want your children and yourself to be healthy, avoid these products. Instead, give your children plain, homemade muesli with fruit – preferably something like the classic Bircher muesli – which is what we often eat in my house.

You should also be careful with fruit juices and yellow, ripe banana – they are almost all sugar. Green, unripe bananas, on the other hand, are loaded with fibre – they are at their best when it is hard to peel away the peel. People in Asian countries eat yellow bananas when they want to gain weight and green bananas when they want to lose weight – and it works. Also refrain from visits to the café, tea parties and church coffee hour – where sugar is in everything that is served. The way I look at it, these are rather out-dated phenomena that have run their course and can be relegated to the museum as an example of the way we once lived. Instead, invite over guests who want nothing more than a good glass of wine, preferably red wine, which is rich in antioxidants and very low in sugar. That is a much better choice for your health – believe me.


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