The change of the staple diet of black South Africans from sorghum to maize (corn) is the cause of the epidemic of squamous carcinoma of the oesophagus
Introduction
Until the 1950s carcinoma of the oesophagus was comparatively rare in the Black population. At the South African Institute for Medical Research in Johannesburg from 1912 to 1927, no cases of oesophageal cancer were diagnosed in Black patients, although over 200 primary hepatocellular carcinomas of the liver were encountered [1]. In the three year survey (1953–1955) of Higginson and Oettle [2] 53 cases were diagnosed. In 1960 the histopathology laboratory at Baragwanath Hospital yielded 87 cases. The 10-year survey (1966–1975) at the same hospital by Isaacson [1] yielded 1331 cases with a male: female ratio of 5:1. The current incidence at Baragwanath hospital is more than 1 case per day.
Dietary factors may be important in the predisposition to oesophageal cancer [3]. In 1975 Ivankovic et al. [4] suggested that nitrosomines might play a role. Several authors have suggested mouldy cereals containing the fungus Fusarium moniliforme, may contain carcinogenic substances, which may play a role in the causation of oesophageal cancer [5], [6]. The induction of oesophageal cancer experimentally by diethylnitrosamine has been known for many years [7]. A role for nitrosamines in humans has not yet been demonstrated. Neither has a definitive role for Fusarium been elucidated.
For many years the staple diet of the Black people of South Africa was sorghum. From approximately the turn of the 20th century, maize (corn) gradually replaced sorghum. The reason for this was probably economic in that the yield from corn is greater. It is suggested that the transformation from sorghum to corn as the staple food plays a significant role in the aetiology of squamous carcinoma of the oesophagus in Black South Africans.
This hypothesis links the roles of Fusarium, nitrosamines, sorghum and corn.
Section snippets
Hypothesis
Numerous articles have demonstrated the presence of Fusarium (or its toxin fumonisin) in mouldy corn [8]. Qui et al. [9] detected high fumonisin levels from 95% of corn samples in areas endemic for oesophageal cancer, whereas the values were statistically lower in specimens from an area with a low incidence of the tumour. Van der Westhuizen et al. [10] showed that the fumonisin levels in corn from the State of Catarina, Brazil, were similar to the high levels determined in other high
Start of the epidemic in the mid 20th century
When the staple diet of the Blacks of South Africa was sorghum, squamous carcinoma of the oesophagus was infrequent. Does Fusarium grow with ease on sorghum? The answer is in the negative. Visconti and Doko [13] examined strains of Fusarium isolated from a variety of cereals including corn and sorghum. The highest production of fumonisin was obtained from corn, followed by wheat and barley. The production of fumonisin from sorghum was 2 orders of magnitude lower than from corn. Moretti et al.
Squamous carcinoma of the oesophagus in countries where sorghum is the staple diet
Several countries in West Africa, including Nigeria and Senegal consume sorghum as the staple diet. Nigeria is probably the biggest producer of sorghum in the world [15]. Pindiga et al. [16] from Nigeria did a retrospective analysis of 177 histologically confirmed cases of oesophageal carcinoma at the University College Hospital in Ibadan over a period of 30 years. Oesophageal carcinoma constituted 0.6% of all malignant neoplasms and 1.4 cases per 1000 surgical biopsies during the study period.
Squamous carcinoma of the oesophagus is more frequent in males
The traditional beer, which the Black people of South Africa drink, is produced by fermenting maize. Considerably more males than females drink beer [18]. In addition, patients with carcinoma of the oesophagus drink more traditional beer than controls [19].
Conclusions
There is an epidemic, of comparatively recent origin, of squamous cell carcinoma of the oesophagus in Black South Africans. This appears to be diet related and a result of the replacement of sorghum by maize as the staple food. Fusarium fungi grow with ease in corn and synthesize nitrosamines. Nitrosamines are carcinogenic. Fusarium does not flourish in sorghum. Traditional beer is produced by fermenting maize. Males consume considerably more beer than females, which accounts for the higher
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