(Author of In the Cauldron of Disease)
THE question as to whether bran is digestible or not was definitely settled twenty years ago by elaborate experiments made by the foremost scientists all over the world, who all arrived at the same conclusion, i.e. that it was digestible. But old fallacies are long-lived, and the bran-bogey still haunts the minds of the majority of doctors and of most bread-manufacturers, who think they are conferring great blessings upon humanity either by discarding bran altogether, or by submitting it to all kinds of new processes in order to make a product, which has proved to be digestible, suitable for human consumption.
It seems therefore of importance to make a survey of the whole question in order to enlighten the minds of at least the bread-consumers, who are the party chiefly concerned and who actually hold in their hands the key to the whole situation. The moment the consumers fully understand this question and act accordingly, the bogey will disappear.
It was the Great War which brought the question as to whether bran is digestible or not “to the front line”, to use a military term. Food became scarce in all the European countries, and the governments naturally turned their attention to the possible nutritive value of all kinds of food which in the previous years of abundance had been discarded or, like the bran, thrown to the cows and pigs with the whole-hearted approval of great medical authorities such as, for instance, Professor Rubner in Berlin.
“Last man die Kleie zur viehfutterung verwenden, so ist das unter allen Umstanden der rationellere Weg.” “If one gives the bran to the cattle for feeding, it is in all circumstances a more rational way of using it”, he says in an article printed in Deutsche Medizinische Wochenschrift, 1915, No. 19.
This sweeping statement was built upon the results of experiments according to which 31.3 per cent. of dry substance, 38.9 per cent. of protein and 73.5 per cent. of carbo-hydrates in bran were digested by human beings, whilst according to Kellner, the great German authority on cattle-feeling, 79 per cent. of dry substance, 79 per cent. of protein and 79 per cent. of carbo- hydrates constituted the maximum percentages absorbed by animals.
How he arrived at these figures is of the greatest interest especially to laymen who have been taught to place implicit faith in the high priests of the medical profession. Rubner himself reveals the secret of the fallacy of his methods in the following paragraph translated literally from the same article:-.
“From observations which I have made on the bran of wholemeal wheat flour which I had washed with water so that only the husks remained, i was able to establish that not less than 68.7 per cent. of dry substance, 61.1 per cent. of the protein and 26.5 per cent. of the carbohydrates were entirely lost to human digestion”.
Rubner now compared these figures with those of Kellner, who had experimented with wholemeal wheat-bran from which nothing had been washed away, and in which consequently all the most easily digestible parts were preserved. That is to say, whilst Kellner made his experiments with the whole of the bran, Rubner confined his to the hardest and least digestible parts, without noticing the fundamental difference between the stuffs with which he and Kellner had been experimenting.
In comparing his results with Kellners he naturally came to a very unfavourable conclusion as to the utilization of bran as food by human beings. This huge mistake is largely responsible for the introduction of the “bran- bogey” into the scientific world, which unfortunately still haunts the minds of so many doctors. It will obviously take more than a generation to disperse it.
Great confusion has been caused in this matter by writers not stating clearly what they mean by “bran”. There is a vast difference between using the world for the cellulose part of the grain only and using it for all the constituents of the grain which are left over from grinding.
By grinding, 70, 80, or 90 per cent. flour may be obtained with a corresponding residue of bran , in which cases the nutrient properties of the bran would differ accordingly. When the percentage of the grinding is not clearly stated little or no value can be attached to subsequent statements as to the digestibility of bran.
Dr. M. Hindhede, Superintendent of the Danish State Laboratory for Food Research, was one of the first scientists in Europe to establish the nutritive value of bran used as food human beings. He had been brought up on wholemeal bread which was used largely as a standard item in the daily food of the Danish farmers, and he could not possibly believe that it would be better to feed the cattle on the bran and eat white bread instead.
Subsequent experiments which he made in his laboratory proved that he was right. He found that his test-subjects digested 67 per cent. of dry substance, 42 per cent. of the protein and 74 per cent. of the carbo-hydrates of a 30 per cent. bran, i.e. bran from 100 per cent. wholemeal grain from which 70 per cent. of white flour had been ground.
By using sifted bran, i.e. bran from wholemeal flour from which 3.8 per cent. had been sifted away, and 96.2 per cent. had been used for wholemeal bread, Hind-hede found that 77 per cent. of the dry substance, 70 per cent. of the protein and 78 per cent. of the carbo-hydrates of the sifted bran were digested. He now compared these figures with those Kellner had obtained by feeding pigs, which digested 67 per cent. of the dry substance, 75 per cent. of the protein and 66 per cent. of the carbo-hydrates; and by feeding ruminants, which digested 69 per cent. of the dry substance, 79 per cent. of the protein and 71 per cent. of the carbo-hydrates, and concludes:.
“These figures show that the ruminants and the pigs digest the protein of the bran better than man himself, whilst man appears to digest carbo-hydrates better than the animals”.
Hindhedes experiments were closely examined by Professor I.E. Johansson, Professor of Physiology at the Caroline Medical Institute, Stockholm, one of the foremost medical institutes in the world, who came to the following conclusion, printed in Svenska Lakaresallskapets Forhandlingar, 1917, page 302 :.
“Hindhedes experiments, which I have just quoted, provide us with an unquestionable standard by which to judge the digestibility of bran. The only possible criticism I could make would be that his test-subjects had for a long time been accustomed to living on vegetable foods, and were therefore likely to be able to utilize the bran better than those who had lived on a mixed diet”.
Johansson now started experimenting with test-subjects who had lived on a mixed, diet, and with wheat-bran taken from a 75 per cent. grinding, i.e. his bran was one-sixth coarser than Hindhedes, and arrived nevertheless at the following figures : digested protein 49, and carbo-hydrates 70, whilst Hindhede, experimenting with a 75 per cent. grinding, had obtained digested protein 42, and carbo-hydrates 74; and with a finer grinding, digested protein 70, and carbo-hydrates 78.
Professor Johansson concludes the report of his research on the digestibility of broad bran with the following words :.
“It us if great interest that broad bran proves to be digestible to such an extent by the intestinal canal of man. The loss of the protein constituents of wheat-bran amounts to only 50 per cent., and of the carbo-hydrates to only 30 per cent. Of the potential nutritive (calorific) value of bran, not less than 64 per cent. is utilized. The bran used in these experiments was obtained from a 75 per cent. grinding, and the loss in nutritive value by discarding the bran amounts therefore to a loss of not less than 14 to 16 per cent. of the total nutritive value of the grain as food for human consumption”.
Hindhedes experiments aroused great interest, especially in Germany and Switzerland, and caused some scientists in these countries to reconsider the question as to the digestibility of bran, among them Dr. G. Wiegner, Professor of Agriculture at the technical High School, Zurich.
Wiegner had been approached during the war by a prominent manufacturer who asked him point-blank: “How does man digest bran?” Wiegner answered with his best scientific conscience : “As far as I know, not at all.” “Very well then”, said the manufacturer, “how do our domestic animals digest it ?” Wiegner answered : “The ruminants very well, the pigs fairly well, almost 60 per cent.” “Then why on earth dont we give the bran to the animals instead of baking it uselessly into our bread ?”.
This question haunted Wiegners mind. When he came across Hindhedes experiments he thought it a perfect scandal that so little had previously been done to find out definitely what was apparently so easy to prove, but which nobody but Hindhede seemed to have cared to put to a thorough test. “Here we have scientific opinions clashing with each other on a question which is of the utmost importance for the welfare of the people,” he said to himself. “
