“Ideas, like living organisms, have their natural history, growing from conception through a more or less tumultuous adolescence and reproductive maturity to an old age, when they act as a bar to further progress. During this time they become so modified that their origin is obscured” Sir Richard Doll (1)
Looking at the occurrence of a disease in time and place, and assessing what might have influenced changes, is known as the science of epidemiology. The theory, that diverticular disease (DD) was caused by low levels of fibre in the diet, has been prominent for about 40 years. This was based on the rarity of DD in Uganda compared with Western countries such as Great Britain or the USA. It was assumed that high levels of fibre in the Ugandan diet protected people from DD and that an increase in dietary fibre would prevent DD and its symptoms would be eliminated. This was a conclusion too far. It ignored the rarity of DD in people eating very little fibre (2,3) and that vegetarians can get DD (4,5). There is no evidence that a high fibre diet prevents DD. The theory is so entrenched that if DD appears in a country then it is assumed that its inhabitants have changed from their normal to a low fibre western diet. This is particularly incongruous when applied to right-sided DD in the caecum and ascending colon. Even the theory’s originators thought low fibre levels could not be relevant to this area (6)
Data from post-mortems, mortality statistics and surveys can provide information on the occurrence of DD, each aspect contributing to the overall picture. Song et al. (7) showed how colonoscopy findings, over time, could plot a rising prevalence of DD in Korea. Jun and Stollman in 2002 (8) collected results from research papers on the % of patients with DD in series of examinations by colonoscopy or barium enema Xray. They used these results to show that changes in the prevalence of DD varied greatly in time and between countries. Searching through later research reports mainly in the PubMed website gives this type of information for many more countries. (References to these sources are too numerous to include here). The results fall into 4 distinct patterns of when DD appeared and how numbers have changed over time until 2010. (more…)