Alexander R.P. Walker

Colonic cancer--hypotheses of causation, dietary prophylaxis, and future research.

Colonic cancer is rare in primitive populations. In western populations it was uncommon in the past, but now accounts for about 3% of all deaths. The cause almost certainly lies with dietary changes. Probably, alterations in bowelmilieu interieur, from interaction between metabolites and microbacteria, promote carcinogenesis. Changes in intakes of protein, fat, sugar, refined cereal products, and crude fiber have been advanced as predisposing or causative factors. Evidence suggests that (i) fall in fiber intake, but (ii) rise in fat intake, in their ability to increase fecal concentrations of bile acids and sterols (possible precursors of carcinogens) are most likely to be culpable. As preventive measures, a significant rise in fiber intake is practicable only from regular bran ingestion. A major reduction in fat intake is grossly unlikely. Even were rigorous dietary changes implemented, an early fall in colonic cancer incidence is highly improbable due to the long-term character of the disease. Future research must include characterization of the diet, metabolism, and disease pattern of segments of western populations who have low colonic cancer mortality rates; also, elucidation of the bearing of various intakes of different food components on the biochemistry and microbiology of the feces.Colonic cancer is rare in primitive populations. In western populations it was uncommon in the past, but now accounts for about 3% of all deaths. The cause almost certainly lies with dietary changes. Probably, alterations in bowelmilieu interieur, from interaction between metabolites and microbacteria, promote carcinogenesis. Changes in intakes of protein, fat, sugar, refined cereal products, and crude fiber have been advanced as predisposing or causative factors. Evidence suggests that (i) fall in fiber intake, but (ii) rise in fat intake, in their ability to increase fecal concentrations of bile acids and sterols (possible precursors of carcinogens) are most likely to be culpable. As preventive measures, a significant rise in fiber intake is practicable only from regular bran ingestion. A major reduction in fat intake is grossly unlikely. Even were rigorous dietary changes implemented, an early fall in colonic cancer incidence is highly improbable due to the long-term character of the disease. Future research must include characterization of the diet, metabolism, and disease pattern of segments of western populations who have low colonic cancer mortality rates; also, elucidation of the bearing of various intakes of different food components on the biochemistry and microbiology of the feces.

effects of transition on bowel diseases in sub-saharan Africans

In populations in sub-Saharan Africa, transitional changes in patterns of morbidity and mortality are taking place, with decreases in the diseases of poverty and infection, but rises in chronic diseases of prosperity, associated, however, with greater longevity. Remarkably, bowel diseases - appendicitis, diverticular disease, colon cancer - while nearly absent in rural areas, have very low incidences in urban dwellers, despite rises in risk factors, including a decreasing intake of fibre-containing foods. Currently, there is no explanation for the phenomenon, which stands in marked contrast to the considerable rises which have occurred in dental caries, obesity in women and diabetes.

Diverticular Disease in Urban Africans in South Africa

At Baragwanath Hospital, Johannesburg, South Africa, during a 3-year period diverticular disease was diagnosed in 42 Black patients (16 men, 26 women), from an urban population approaching 1,5 million. Patients presented mainly with rectal bleeding, abdominal mass or pain. Of average age 62 years, all were among the more privileged. The persisting very low frequency of the disease, which is in consonance with low frequencies of other bowel diseases (appendicitis, ulcerative colitis, colon cancer), is deemed valid. The mean daily dietary fibre intake, 26.5 +/- 8.5 g, was higher than that of local Whites, 22.4 +/- 6.0 g, but significantly less than that of a sex-age matched urban Black control group, 32.5 +/- 11.4 g. Although a measure of westernization of diet has obviously occurred, its extent, also the period of exposure, would seem to have been insufficient to have evoked significant rises in the occurrence of diverticular disease.

Serum high density lipoprotein cholesterol levels in african schoolchildren living near or very far from school

In African populations, coronary heart disease (CHD) is rare, Serum high density lipoprotein (HDL) cholesterol levels, negatively associated with CHD, understandably are significantly higher in African children and adults, compared with their White Counterparts. On enquiring into the role of physical activity, observations at 3 rural African schools showed that children of 10-12 years, who regularly walked long distances attending school (average about 10 km daily) had only slightly (although significantly) elevated mean HDL cholesterol levels, compared with groups who lived near by. It is considered that the diet of pupils (inter alia, having low fat and high fibre contents), associated with the high level of activity which prevails generally, share responsibility for their high HDL cholesterol levels.

Data are not now collected by ethnic group in South Africa

Editor–Claire Hilton notes that since April 1995 British hospitals have had to collect data on each patients ethnic group.1 In the United States this is standard practice. In the Morbidity and Mortality Weekly Report data on numerous variables relating to the health and ill health of black and white people are regularly given2–as also, on occasion, are data on Hispanics, American Indians, Inuits, and Pacific Islanders. In South Africa precisely the converse has occurred. Ethnic subdivisions have stopped appearing …

Appendicectomy prevalences in South African adolescents.

From questioning 16,939 South African pupils of 16-18 years, in 56 high schools, mean prevalences of appendicectomies in representative segments of ethnic groups were found to be: rural Blacks 0.6%; urban Blacks 0.7%; Indians, 2.9%; Coloureds (Eur-African-Malay), 1.7%; Whites, 10.5%. Percentages in the sexes were similar. Only those of Indian and Coloured pupils appear to be increasing. Blacks and Whites, respectively, have high and low intakes of fibre-containing foods, which are negatively correlated with appendicectomy prevalences. However, although intakes of fibre-containing foods are slightly higher in Indians and Coloureds than in Whites, the formers appendicectomy prevalences are lower than would be dietarily expected.

Serum lipids in long-lactating African mothers habituated to a low-fat intake

African women, accustomed to a low fat intake, have relatively low blood lipid levels, and are virtually free from coronary heart disease. Among lactating mothers, the amount of fat voided daily in their breast milk is of the same order as that ingested in their habitual diet. However, investigations showed that long-lactating mothers, compared with appropriate control groups, did not exhibit significant hypolipidaemia.

Biosynthesis of vitamin C

The vast majority of animals and plants are able to synthesize vitamin C, through a sequence of enzyme-driven steps, which convert monosaccharides to vitamin C. In plants, this is accomplished through the conversion of mannose or galactose to ascorbic acid. In some animals, glucose needed to produce ascorbate in the liver (in mammals and perching birds) is extracted from glycogen; ascorbate synthesis is a glycogenolysis-dependent process. In reptiles and birds the biosynthesis is carried out in the kidneys.