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Climb Off the Bran Wagon
Part 3: Oat bran — the wonder fibre?
Oat bran is regarded as a 'healthy' cholesterol-lowering food. It is advertised with statements such as 'recent medical research shows that oat bran could actually lower your cholesterol level.' This is based, apparently, on an experiment conducted at Northwestern University, Evanston, Illinois, in 1986, which involved only 208 subjects, lasted just six weeks and whose results were not statistically significant.17 Despite this, an oat bran campaign in the US saw sales of oat bran cereals increase 240% by 1989.
More recent medical research has come up with very different findings. Results of an American study into the effects of oat bran showed that oat bran was not the cure-all it had been claimed to be — just another example of dietary advice that is 'without foundation' and 'verging on quackery'.18 In this test, people were fed 100 grams of oat bran per day (three times the recommended dose), the placebo (control) group having 100 grams of a white flour, low-fibre placebo. There was no appreciable difference in blood cholesterol levels between the two groups. The authors said: 'Some dietary fibres do bind bile acids and thus may have a cholesterol-lowering effect similar to that of the bile-acid-sequestrant drugs. However, many experiments, both in outpatients and in metabolic wards, have failed to demonstrate that wheat bran does, in fact lower plasma cholesterol levels.' They then said that: 'oat bran had no effect over and above that of the wheat placebo. It did, however, produce gastrointestinal rumbling and some discomfort.'
Another American study published the same year also had similar findings, and concluded: 'As we also found, low-fibre products can achieve the same result with fewer gastrointestinal side effects.'19
The following year oat bran was tested in people with high blood cholesterol levels.20 Using 30, 60 and 90 grams of oat bran per day, they found that it made not the slightest difference either to total cholesterol levels or to levels of low density lipoprotein (LDL).
That rules out cereal fibre. Could other plants that also contain fibre be better?
Fruit and vegetables contain quite small amounts of fibre (see Table 1) 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.
| Food |
Fibre g/100 grams |
Fibre g/100 kilocalories |
| 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 |
We know, then, that an increase of the right kind of fibre in the diet may lower blood cholesterol. The important question is: will it also lower the risk of heart disease? The various multifactoral intervention trials tested this and all had to conclude that increasing dietary fibre had no effect on heart disease. In addition, there is really no direct evidence that an increase of fibre by itself will prevent or cure any of the other diseases.
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.21 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 because of the lack of evidence that fibre protects against cancer.
Fibre pills for obesity
In a UK pharmacist, Boots the chemist, I saw fibre pills which, their label claimed, would reduce obesity. Each pill contained 0.2 grams of fibre and the recommended dose was four to six pills before each meal or when one feels hungry. Its makers claimed that fibre stays in the stomach longer and so wards off the pangs of hunger. There are two points to be made here: firstly, that the theory on which the fibre hypothesis is based is that it does not stay in the gut longer but that it moves through quickly and, secondly, that even if it did stay in the stomach, around one gram (five pills) would have no effect whatsoever. It is about the amount of fibre one would find in one dried prune.
Last updated 1 April 2010
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