CLIMB DOWN FROM THE BRAN WAGON

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The tragedy of science is the slaying of a beautiful hypothesis by an

ugly fact. T H Huxley

 

In years to come, the past couple of decades of the twentieth century

may well come to be known as 'The Bran Age'; a time when it seemed that

most of the diseases of Western civilisation were being blamed on a lack

of fibre in the diet, and we were all being exhorted to eat as much as

possible to cure or prevent those diseases. Diseases blamed on a lack of

dietary fibre include: intestinal diseases such as cancer of the colon,

appendicitis, constipation and irritable bowel syndrome as well as

coronary heart disease, diabetes, obesity, deep vein thrombosis,

varicose veins, hiatus hernia and gallstones.

 

What is fibre?

 

In a nutshell, fibre is that part of a vegetable which passes undigested

through the human gastrointestinal tract. The major natural source of

fibre is the cellulose that forms plant cell walls but there are a

number of other kinds of fibre. The ones that scientists are interested

in most are cellulose, hemicellulose, lignin and pectin.

 

Origins of the recommendations

 

The belief that regular bowel movement is important for health is very

ancient. In 1932 a 'New Health' movement was promoted in which people

were urged to include plenty of roughage in their diets and it was hoped

then that the prompt passing of stools after each substantial meal would

reduce the incidence of intestinal disease. (1) Thirty years later Dr

Dennis Burkitt, while working as a doctor in Africa, discovered that

there was a much lower incidence of cancer of the colon among rural

black Africans than among Europeans and Americans. He attributed this

low incidence to their relatively crude diet. (2) The theory was that

fibre hastened the passage of the bowel contents thus allowing less time

for cancer-inducing agents to form. This, of course, presupposed that

food became carcinogenic in the gut and there was no evidence that it

did. Neither was there any evidence that moving food through the

intestine at a faster rate decreased the risk of cancer.

 

So the theory was unsubstantiated then by evidence and later it was to

be disproved in practice when it was noticed that, when the rural

Africans moved into towns and adopted a Western style low fibre diet,

they continued to have a low incidence of colon cancer. A pattern which

has also continued with the second generation. It should also be noted

that the rural Africans' lifestyle is quite different from that of the

Western city dweller: their diet is different in that their energy

intake is lower and they eat less protein, fat and sugar, but they are

also not exposed to so many pollutants, toxins or mental stresses and

any of these factors could be responsible for the difference in disease

patterns. Other studies have also shown that there are Western

communities (the Mormons of Utah, for example) who also enjoy a low

incidence of colon cancer but eat a low fibre diet. (3) Nevertheless,

the later findings were not publicised, Burkitt's theories caught the

attention of the media who are always ready to exploit a good story.

They expanded what was at best a very weak hypothesis into the treatment

dogma of today which teaches that fibre is a panacea for all manner of

illnesses. (4)

 

But it would be unfair to heap all the blame on the media. Commercial

interests were quick to see the potential in the recommendation.

Although Burkitt's recommendations were based on vegetable fibre, bran

has a far higher fibre content than vegetables and bran was a

practically worthless by-product of the milling process which, until

then, had been thrown away. Now, virtually overnight, it became a highly

priced profit maker. Bran is quite inedible - there is no known enzyme

in the human body that can digest it. Nevertheless, backed by Burkitt's

fibre hypothesis, commercial interests could now promote it as a

valuable food. The late John Yudkin, Professor Emeritus of Nutrition and

Dietetics at London University, pointed out that 'perhaps one reason for

the wide acceptance of the suggestion that fibre is an important, if not

essential, dietary component is that it had the enthusiastic support of

commercial interests.' He was writing in particular about the high-bran

products, All Bran and Branslim. (5)

 

Dr Hugh Trowell, another strong advocate of dietary fibre, confirmed

this in 1974, saying that 'a serious confusion of thought is produced by

referring to the dietary fibre hypothesis as the bran hypothesis, for

many Africans do not consume cereal or bran but remain almost free of

constipation, irritable bowel syndrome and diverticular disease'. (6)

 

Bran, very high in fibre, is the tough outer covering of cereal grains.

Every civilisation in history has devised methods and implements solely

for the purpose of separating bran from the grain so that they would not

have to eat it, and even animals in the Third World today, which are fed

bran in their food, reject it.

 

Fruit and vegetables contain quite small amounts of fibre (see Table) so

that if a significantly larger amount is to be eaten, this will have a

dramatic effect on the volume of food consumed. Thus the advice to

increase fibre in the diet, if we are to use 'natural' sources, must

involve a substantial change to the diet as a whole. And that is likely

to be unpopular or we would be eating it already.

 

Table: Amounts of Fibre in Typical Foods

 

Fibre

Food g/100g g/100kcal

Apples, raw

2.0

 

4.3

Beans, haricot, boiled

7.4

 

8.0

Cabbage, winter, boiled

2.8

 

18.7

Carrots, young, boiled

3.0

 

15.0

Potatoes, new, boiled

2.5

 

2.6

Plums, raw

2.9

 

8.0

 

Irritable bowel syndrome

 

The claims made for fibre are based on its rapid transit through the gut

and, because of this property, bran has been a popular way to manage

irritable bowel syndrome (IBS) for since the early 1970s. So, is it

effective? The answer appears to be no. A number of placebo controlled

studies of bran in IBS have not shown any convincing effect of the fibre

on overall symptom patterns. Results of a study from St Bartholomew's

Hospital in London, showed clearly that fifty-five percent were made

worse compared to only ten percent made better. (7) All symptoms of IBS

were exacerbated by wheat bran, with bowel disturbance most often

adversely affected, followed by distension and pain. The authors

conclude: 'The results of this study suggest that the use of bran in IBS

should be reconsidered. The study also raises the possibility that

excessive consumption of bran in the community may actually be creating

patients with IBS by exacerbating mild, non-complaining cases.'

 

When several independent responses were analysed, the only significant

improvements with bran treatment were in constipation; but then a number

of people believe, wrongly, that they are constipated if they miss only

a day. Some patients found that the added bran in their food induced or

exacerbated uncomfortable symptoms of flatulence, distension and

abdominal pain. In these cases, reduction in the amount of bran eaten

was recommended.

 

Colon cancer

 

In addition, there is really no direct evidence that an increase of

fibre by itself will prevent or cure any of the other diseases. As far

as colon cancer is concerned, Burkitt's theory was questioned with the

suggestion that the low cancer rates in rural Africans may be due to

their high early death rates from other causes so that they do not reach

the age at which cancer peaks in Europeans. (8) As Europeans usually

develop it in their seventies and the life-expectancy of Burkitt's

Africans was only around forty, why was it that this suggestion took so

long to arrive at? There is also a growing scepticism in the USA that

lack of fibre causes cancer. And some studies have even suggested that a

fibre-enhanced diet may increase the risk of colon cancer. (9) The idea

that people must tolerate an unpalatable bran-rich diet to ward off such

diseases is founded on extremely dubious hypotheses.

 

It had been shown in the mid-1980s that dietary fibre increased the risk

of colon cancers. (10) In 1990 The British Nutrition Foundation admitted

that the hypotheses that IBS, diverticulosis and colo-rectal cancer are

caused by a deficiency of fibre had not been substantiated, neither have

those that fibre might protect against diabetes, obesity and CHD. (11)

The Seventh King's Fund Forum on Cancer of The Colon and Rectum agreed:

'The Forum commented that cereal fibre does not offer protection against

cancer'. (12)

 

Dr M Inoue, et al published in 1995 an investigation of cancers at

several colorectal subsites: ascending, transverse, descending, sigmoid,

and rectum, within a Japanese hospital environment. They concluded that

loose or soft faeces are a significant risk factor for cancer at these

sites. (13) And bran loosens and softens faeces - that's why it is

recommended.

 

The following year Drs HS Wasan and RA Goodlad of the Imperial Cancer

Research Fund showed that bran can increase the risk of colorectal

cancers. (14) 'Many carbohydrates', they say, 'can stimulate

epithelial-cell proliferation throughout the gastrointestinal tract.

They conclude: 'Until individual constituents of fibre have been shown

to have, at the very least, a non-detrimental effect in prospective

human trials, we urge that restraint should be shown in adding fibre

supplements to foods, and that unsubstantiated health claims be

restricted. . . . Specific dietary fibre supplements, embraced as

nutriceuticals or functional foods, are an unknown and potentially

damaging way to influence modern dietary habits of the general population.'

 

This study spawned several critical letters. It comes as no surprise

that half were from people connected with the breakfast cereal industry.

(15)

 

The results of the largest, long-term trial to date, published in 1999,

also suggest that, contrary to popular belief, high dietary fibre intake

does not protect against colorectal cancer. (16) Researchers at Harvard

Medical School and the Dana-Farber Cancer Institute, both in Boston,

Massachusetts, studied 88,757 women over sixteen years. They say:

 

'no significant association between fiber intake and the risk of

colorectal adenoma was found'. But there was what they call an

'unexpected' finding, in that, according to their data, a high

consumption of vegetable-derived fiber was actually 'associated with a

significant increase (35%) in the risk of colorectal cancer'. They

conclude 'Our data do not support the existence of an important

protective effect of dietary fiber against colorectal cancer or adenoma'.

 

.. . . and breast cancer

 

It has been claimed that elevated fruit and vegetable consumption is

associated with a reduced risk of breast cancer. To test this, twenty

named researchers at seventeen cancer research centres in the USA,

Germany, Netherlands, and Sweden examined the association between breast

cancer and total and specific fruit and vegetable group intakes. Their

studies included 7,377 incident invasive breast cancer cases occurring

among 351,825 women. They found no association for green leafy

vegetables, 8 botanical groups, and 17 specific fruits and vegetables

and conclude:

 

" These results suggest that fruit and vegetable consumption during

adulthood is not significantly associated with reduced breast cancer

risk " . (17)

 

Clearly there are two sides to this debate and claims of benefit are by

no means proven. That, of course, does not stop a variety of commercial

interests from jumping on a very lucrative bran-wagon.

 

When the American Heart Association published its dietary

recommendations in 1982, the US National Cancer Institute (NCI) and

Kellogg's got together to promote All Bran. (18) But by making such

health claims, Kellogg's effectively turned All Bran from a food into a

drug - and drugs must be approved by the Food and Drugs Administration

(FDA). This gave the FDA a problem as the NCI had already given its

blessing to All-Bran. They have an even bigger problem now as these

later studies, by and large, do not support the claims that fibre has a

protective role in cancer.

 

Other adverse effects from fibre

 

Tests into the supposed benefits of increasing dietary intake of fibre

soon showed that there could be other harmful side-effects:

 

* Because it is indigestible, bran ferments in the gut and can

induce or exacerbate flatulence, distension and abdominal pain. (19)

* Although it is supposed to travel through the gut at a faster

rate, it does not always do so and it has been shown to cause blockages.

(20)

* All the nutrients in food are absorbed through the gut wall and

this takes time. It should be obvious, therefore, that if the food

travels through faster, less will be absorbed. And, indeed, this is the

case. Fibre is found to inhibit the absorption of zinc, (21) iron,

calcium, phosphorus, magnesium, energy, proteins, fats and vitamins A,

D, E and K. (22)

* Phytate associated with cereal fibre (bran) also binds with

calcium, iron, (23) and zinc, (24) causing malabsorption. For example,

subjects absorbed more iron from white bread than from wholemeal bread

even though their intakes of iron were fifty percent higher with the

wholemeal bread. (25) Also, while white bread must have added calcium,

the law does not require it of wholemeal bread.

* Bran fibre has also been shown to cause faecal losses, (26) and

negative balances of calcium, (27) iron, zinc, phosphorus, (28)

nitrogen, fats, fatty acids and sterols thus depleting the body of these

materials. (29) (A negative balance is where more is lost from the body

than is absorbed, i.e. the body's stores are depleted.)

 

The findings, particularly in sub-paragraphs c. to e. above are a cause

for concern in several sections of the population who are at

considerable risk from eating too much fibre - and bran fibre in particular:

 

* Post-menopausal women stand a 1 in 2 chance of suffering from

osteoporosis (brittle bone disease) and 1 in 5 of them will die as a

direct result. (30) That is twice as many as many fractures as there

were in the 1950s. (31) Osteoporosis is caused by a number of things,

but it is basically a calcium deficiency which is at the heart of the

disease. Very few surveys have concentrated on intake of any nutrient

other than calcium and more research is needed on this subject. However,

as the eating of bran both inhibits the absorption of calcium from food

and depletes the body of the calcium it has, is it coincidence that the

incidence of osteoporosis has increased by about ten percent a year for

the past two decades? In England alone, a fifth of all orthopaedic beds

are now occupied by patients with broken hips and the direct hospital

costs alone amounted to more than £160,000,000 a year over a decade ago.

(32) That figure did not include other breakages, personal costs and, of

course, the pain and hardship brought on by the disease. Broken bones

also require zinc for their repair, and zinc is another mineral whose

absorption is adversely affected by cereal fibre.

* Calcium also plays an important role in the processes that keep

normal body cells normal. Imbalances in these processes can have such

adverse consequences as acute disruption leading to rapid cell death,

and start other processes which lead to the deregulation we call cancer.

Recent studies have shown that increases in dietary calcium may protect

against cancer of the colon. (33) From this must follow that if calcium

is not available because of the amount of bran in the diet, the risk of

such cancer may be enhanced.

* Patients with Alzheimer's disease (senile dementia) have been

found to have abnormal amounts of aluminium in their brains. Tests on

the people of Guam and parts of New Guinea and Japan, who get the

disease at a much younger age, have linked it too with a lack of

calcium. It is suggested that the lack of calcium causes a hormonal

imbalance which allows the aluminium to penetrate the brain. (34)

* Infants can suffer a similar brain damage if fed soya based baby

milk. (35) Soya based milk has a high phytate content which, as we have

seen, inhibits the absorption of some minerals. (36) It is believed that

a zinc deficiency so caused enhances the uptake and deposition of

aluminium in the milk.

* Depression, anorexia, (37) low birth weight, (38) slow growth,

(39) mental retardation, (40) and amenorrhoea are also associated with

deficiencies of zinc and the first five of these are also associated

with a deficiency of iron (see sub-paragraph g. below).

* Vitamin deficiency diseases such as rickets are also increasing.

Such diseases are common in communities where a nutrient poor, fibre

rich diet is consumed, and rickets was so common in this country early

in the century, that it was called the 'English disease'. All such

diseases in this country should have been relegated to the past but now

they are on the increase again. (41) Studies of UK Asians, in which the

incidence of rickets is high, cite as the cause the Asians' low-calcium,

high-cereal diet. (42)

* If there is a large intake of 'anti-nutrients' such as phytate,

dietary fibre and tannins, which impair the absorption of iron, (43) and

a low intake of flesh foods (another result of the diet-heart

recommendations), there is a real risk of iron deficiency anaemia. And

sub-optimal iron nutriture is already found in UK, USA, Canada and South

Africa. (44)

* Lastly, there is an apparent relation between dietary fibre and

reproductive function in the female. It affects the onset of

menstruation and retards uterine growth. (45) Later it is associated

with menstrual dysfunction. (46)

 

Although most of the experimental studies conducted using fibre

consumption of 30-40g/person/day and with supplements added in the range

ten to thirty grams per day (which are broadly around the levels

recommended) had little adverse effect, tests on mineral availability do

suggest that excessive consumption would have significant undesirable

effects on mineral status. It would appear, therefore, that although a

modest increase of vegetable fibre would probably not have any

significant adverse effects, provided that there were adequate amounts

of proteins, minerals, etc in the diet, any advice must be given in such

a way as to prevent the excessive intake of phytate associated with

cereal fibre (bran). Incidentally, as a breaker of teeth, Granary Bread

is second only to a punch in the mouth.

 

Men only

 

Professor David Southgate is a world-renowned expert on dietary fibre.

He concludes that the effects of excessive intakes of dietary fibre on

calcium, iron and zinc absorption would be particularly undesirable for

infants, children and young adolescents, and recommends that dietary

fibre intakes in those groups should be separated from those for the

general adult population and given on a body-weight basis. (47) To them

should be added pregnant women and post-menopausal women whose mineral

needs are greater and who should also be protected from excessive

consumption of fibre.

 

The advice given by dieticians, nutritionists and doctors appears to

include no caveats concerning age, sex or body weight. Indeed, the

impression given by them all is that we should all eat as much fibre as

we can tolerate. The British Medical Association in its publication The

Slimmers' Guide , even recommends bran as a good source of calcium! (48)

Not unnaturally, the makers of All-bran and similar breakfast cereals,

and wholemeal breads bombard us via television advertisements stressing

the goodness contained in their products by virtue of the high bran

content. Yet the only members of the population who may eat these in any

quantity with relative impunity are adult men.

 

Conclusion

 

What we have then is evidence that consumption of fibre - and bran in

particular - may be hazardous.

 

There are conflicting reports, some of which implicate fibre as

increasing the risk of the cancers it is supposed to protect against.

There is also a similar danger of malnutrition in the many sections of

society.

 

It is unlikely that eating bran is of benefit to any section of society.

There is a limit under which bran may not be harmful - but we have no

ready way to know what that limit is. Therefore, it is much safer for

you to avoid bran than to try to gauge what your safe limit might be.

And if you do suffer from constipation, you would be better advised to

drink more water. A minimum of four pints a day should do it.

 

References

 

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1932: 127.

 

2. Burkitt D P, et al. Some geographical variations in disease patterns

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3. Lyon JL, Gardner JW, et al . Low cancer incidence and mortality in

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4. Smith J. Nutrition and The Media. In MR Turner, ed . Preventative

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5. Yudkin J. Food for thought. Br Med J 1980; 281: 1563.

 

6. Trowell H C. Fibre and irritable bowels. Br Med J . 1974; 3: 44.

 

7. Francis C Y, Whorwell P J. Bran and irritable bowel syndrome: time

for reappraisal. Lancet 1994; 344: 39.

 

8. Moore T. Dietary fibre: food or fetish? Lancet 1986 i: 1040.

 

9. Kritchevsky D. Fibre and cancer . in G V Vahouny and D Kritchevsky

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10. Dietary studies of cancer of the large bowel in the animal model .

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21. Sandstrom B, et al. The effects of vegetables and beet fibre on the

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22. Kelsay J L. Op cit.

 

23. Hallberg L, et al. Phytates and the inhibitory effect of bran on

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24. Turnlund J R, et al. A stable isotope study of zinc absorption in

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25. Kelsay J L. Op cit.

 

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27. Balasubraminian R, et al. Effect of wheat bran on bowel function and

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34. BBC. Horizon: The Poison That Waits . BBC2 broadcast 16 Jan. 1989.

 

35. Bishop N, McGraw M, Ward N. Aluminium in infant formulas. Lancet .

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38. Meadows N, et al. Zinc and small babies. Lancet . 1981; ii: 1135.

 

39. Lifshitz F, et al . Nutritional dwarfing in adolescents. Semin

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44. Bindra G S, Gibson R S. Iron status of predominantly

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45. Hughes R E, Johns E. Apparent relation between dietary fibre and

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1987; 46: 681.

 

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48. BMA. The Slimmers' Guide . Family Doctor Publications, 1988. Latimer

Trench & Co Ltd. Plymouth.

 

Last updated 26 March 2001