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Nutritionists have been telling us to pump up the fibre in our diet for 44 years. But the evidence is now in. Not only is that pointless. In at least one case, it is very likely to be harmful.

In 1971, Dr Denis Burkitt, an Irish Surgeon, published a paper based on his observations of life in Uganda, where he lived at the time. In it he hypothesised that a lack of dietary fibre was the cause of much that then ailed Western Society. He thought it caused bowel cancer and probably also heart disease, Type II Diabetes, varicose veins, obesity, diverticular disease, appendicitis, gallstones, dental cavities, haemorrhoids, hernias and constipation.

Dr Burkitt had noticed that native Africans produced on average four times as much poop as English boarding school children and did so at three times the speed. He felt that this was because of all the fibre they ate. And he theorised that the, ah, high rate of flow meant that there was less time for cancer causing foods and impurities to be in contact with our insides.

It was an idea whose time had come and the good doctor quickly became ‘fibreman’, releasing a best-selling book on the topic (a page-turner called ‘Don’t forget Fibre in your Diet’) and crusading ceaselessly for the addition of fibre to the Western diet. He is famously quoted as saying “America is a constipated nation…. If you pass small stools, you have to have large hospitals.”

His simplistic guess was swallowed whole by the medical and nutrition communities and heavily promoted by those who stood to gain the most from it (largely the Breakfast Cereal Manufacturers).

The shopping list of things fibre is supposed to prevent has gotten shorter as science has delivered better evidence on their real causes but it is still impressive.

To this day, the DAA (Dietitians Association of Australia) claims that eating ‘at least 25-30 grams of fibre a day’ will ‘reduce the risk of constipation, diverticular disease, haemorrhoids and bowel cancer.’ They also mention it will ‘lower the risk of [heart] disease.’

Unfortunately (as is often the case with claims made by the DAA) there is no credible evidence that any of that is true.

Bowel Cancer

In 2002 the highly respected Cochrane Collaboration reviewed five high quality randomized controlled trials involving 5,000 patients. They concluded that there was no evidence to suggest that increased dietary fibre would reduce Bowel Cancer.

That review was followed up in 2005 by a major evidence review by the Harvard School of Public Health. The paper covered 13 studies which involved 725,628 people. And again fibre drew a blank. The authors concluded that high dietary fibre intake did not reduce the risk of Bowel Cancer.

Heart Disease

The theory goes that fibre is supposed reduce heart disease risk by lowering our ‘bad’ cholesterol. Once again though the research community is being singularly unsupportive.

While oats do lower cholesterol, trials on other types of fibre show that it doesn’t, good, bad or otherwise.

And when it comes to the only thing that really matters, there is no evidence that fibre reduces the risk of dying from heart disease (or anything else).

Constipation and Haemorrhoids

Fibre is supposed to cure constipation (and all its travelling companions, including haemorrhoids, bloating, anal bleeding and abdominal pain).

Believe it or not, this is simply based on Fibreman’s observation of high-flow Ugandans. They didn’t seem constipated so ramping up the fibre is sure to cure the Western blockage. Once again though, the evidence has not been kind.

Studies have repeatedly failed to detect that patients with constipation eat less fibre than people without it. Worse (for the Cereal Industry), those studies have observed that there is no benefit for constipation when fibre is added to the diet.

But something really interesting happens when you reverse the treatment. A recent trial measured the effect of removing fibre from the diet of people with constipation, with spectacular results.

Six months after the added fibre was removed, ALL of the (initially) constipated patients no longer suffered from constipation, bloating, bleeding or pain. In contrast the folks who stayed on high fibre diet still had all of those problems.

Diverticular Disease

The news is significantly worse when it comes to Diverticular Disease, an extremely common and painful condition affecting more than half of all people over 70.

As early as 1981, clinical trials were finding that fibre was no help at all. One author even concluded that the suggestion it might was “simply a manifestation of western civilization’s obsession with the need for regular frequent defecation.”

But much more worryingly, one significant recent study concluded not only that fibre didn’t help but that it increased the likelihood of contracting the disease.

The evidence is now in. Just like so much of the dietary nonsense we’ve been fed over the last half century, fibre for disease prevention turns out to be twaddle that benefits nobody except the people flogging us whole grain cereals.

A combination of ignorance, arrogance and negligence (with a sizable smattering of corporate profiteering) has kept the eat-more-fibre message front and centre for all nutritional advice. But we didn’t need added fibre before 1971 and we still don’t need it. Worse, it is likely to be adding to the burden of diverticular disease (at least).

An Irish doctor’s theory about prodigious Ugandan turds has ensured the rest of us have been fed crap for the last four decades. But that needs to stop now. The DAA needs to step up and change the message – even if that is likely to really annoy its cereal selling sponsors.

Image: DAA Corporate Partners (via the Grains and Legumes Nutrition Council)