It is often postulated that diverticular disease is virtually unknown in black Africans who live south of the Sahara in rural environments and who have not changed their traditional high-residue diet (Segal et al., 1977). As many black South Africans began to move from the rural areas to urban industrialized areas around Johannesburg, their social and educational development became more sophisticated than their rural counterparts. When comparing the dietary intake of the two groups of black South Africans, the rural and urbanized, a major difference is seen in fibre intake. The rural diet consists mainly of maize, millet and wheat products, plus beans, dried peas, ground nuts, vegetables and fruit. Milk and meat are not often included in the diet. As a result of the social and educational upward movement of the urbanized black South African who may be in domestic employment, the diet becomes very similar to that consumed by western populations with low fibre and low residue and high in sugar.
In the small study undertaken by Segal et al. (1977) the cohort came from urbanized black south Africans who regularly consumed a high refined carbohydrate diet. The staple diet of the rural black South African, which is maize, was not eaten by the cohort; fruit was rare and vegetables were eaten only once a week. Meat was part of the diet on a daily basis. Radiological studies in the form of barium enemas showed that six patients had isolated diverticula, whereas 10 demonstrated multi-diverticula as would be seen in patients from western countries.
The postulated aetiological relationship put forward in the much quoted Painter and Burkitt paper (1975) appears to be confirmation that a change in dietary fibre intake has a bearing on the association of fibre and diverticular disease. In the South African study the cohort are the first generation who have given up traditional foods and changed from a high to low residue diet.
In studying the Bantu, an African tribe who solely use the healthcare facilities of the Baragwanath Hospital in Johannesburg, Keeley (1958) reviewed the postmortem examinations of 2367 patients between the years 1954 and 1956 for diverticulosis. Of this group 789 were over 45 years of age. The incidence was just one case. Clinically and radiologically, diverticulitis had been identified only once. A. Solomon, in a personal communication in 1969 to Painter and Burkitt (1975), had, in a 3-year period to 1971, reported six cases of diverticula in 1000 consecutive barium enemas.
In Kampala, only two cases of diverticula were identified by Davies (quoted in Trowell, 1960) from 4000 postmortem examinations in 15 years. In other areas of Africa, Nairobi, Congo, Durban and Ghana over periods of surgical experience ranging from 8 to 16 years, diverticula were identified on fewer than 10 occasions (F. Badoe, 1969; D. Chapman, 1969; M.S.R. Hutt, 1970; A. Jain, 1970; J.R. Miller, 1970; A.L. Templeton, 1970 - cited in Painter and Burkitt, 1975). It could be suggested that some facilities in African hospitals are not as good as they are at major hospitals and therefore the incidence of diverticula could easily be missed, but this was unlikely at major hospitals where there was plenty of experience, especially in the pathology department. These results contrast sharply with the results of 221 barium enemas on white South Africans, in whom 20.8% were shown to have diverticula (Segal et al., 1977).
The conclusions of this study appear to be that the ongoing urbanization of the black South African has seen the accompaniment of diverticular disease which had been virtually unknown in this population. The recognition of any disease pattern will depend on the researcher and awareness of the occurrence in a specified population. Consideration must be given to the dietary intake and any other habits such as socioeconomic conditions, geographical origin, and local or tribal customs.
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