December 6, 1980
Dr Yudkin laments that fibre is not essential and that we should turn focus on sugar as cause of diabetes and heart disease.
Food for thought.
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But it would be unfair to heap all the blame on the media. Commercial interests were quick to see the potential in the recommendation. AlthoughBurkitt'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.
Sir,--As Dr N H Dyer says in his review of the Royal College of Physicians' report on dietary fibre, fashions change. 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 enthuiastic support of commercial interests. A press release from the manufacturers of All-Bran says with dogmatic assurance, "A diet deficient in fibre makes people more prone to diseases like appendicitis, diverticular disease, cancer, and heart attacks." The makers of the product Branslim claim that the gram or so of bran it provides before each meal results in a feeling of satiety and so to a reduction in food intake.
Now compare these claims with some conclusions in the report itself (my italics): "There is much evidence of an environmental factor at work in causing appendicitis, and possibly this is a lack of dietary fibre." "Patients with diverticular disease have probably eaten less dietary fiber than their diverticula-free compatriots." "There are reasonable grounds for the statement that, in genetically susceptible persons, large bowel cancer could be favorued by a fibre-depleted diet, but other explanations for the commonness of this cancer in Westernised countries are possible." "It is not yet possible to give specific recommendations to the general public about fibre's value in preventing heart attacks." "Although societies which exist on a fibre-rich diet have a low prevalence of obesity, this is not evidence that dietary fiber as such prevents obesity."
Neverless, it is a pity that the excellence of the report is marred by the continual use of the inaccurate and misleading term "refined carbohydrate" in referring both to sugar and to white bread made from highly milled flour. It is inaccurate because white bread does not consist of pure starch but contains some 12% (dry weight) of protein, as well as significant amounts of vitamins and mineral elements. More important, the term "refined carbohydrate" is misleading because it implies that both sugar (sucrose) and white bread (or indeed starch) have the same effects on the body. But they have very different effects, and these differences are likely to be much more relevant to human disease than are the differences produced by wholemeal bread and white bread.
The major characteristic of Western diets is that, during the last 200-300 years, their total carbohydrate content has not changed much, but the nature of that carbohydrate has changed: the starch content has fallen considerably while the sugar content has risen to about the same extent. The association of "diseases of affluence" with changes in diet is at least as strong for this replacement of starch by sugar as they are for the diminution of dietary fibre.
Dietary sucrose increases the concentration in the blood of cholesterol and triglyceride, and of uric acid and insulin, it also reduces the concentration of high density lipoprotein cholesterol. It leads to a diminution of glucose tolerance. Aggregation and adhesiveness of the blood platelets are increases, as is their electrophoretic mobility in the presence of ADP.
Dietary sucrose also results in several of the abnormalities seen in diabetics. In additon to diminished glucose tolerance and hypelipidaemia, it produces tissue insensitivity to insulin, retinopathy, and nephropathy. The most recent experiments show that the nephropathy is associated with changes in the glomerular basement membrane that are indistinguishable, in histology and in biochemistry, from the changes produced in experimental diabetes. It is tempting to see the production of the characteristics of both coronary heart disease and diabetes by dietary sugar as a clue to explaining the close clinical connection between the two diseases.
It should be stressed that most of these changes occur in experiments with amounts of dietary sugar that are well within the range of the amounts habitually consumed by individuals in Western countries. All of this information is hidden when we use "refined carbohydrate" indiscriminately to mean sugar, or products of highly milled cereals, or both.