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Editor - Boyle and Langman excellently summarized descriptive
features and risk factors of colorectal cancer in the ABC series of BMJ
(30 September 2000). However, it seems that the authors are rather
selective (or not well informed) of recent literature regarding dietary
and nutritional factors in the etiology of colorectal cancer. Boyle and
Langman states that intake of dietary fat and meat is positively related
to risk of colorectal cancer. High intake of meat is probably associated
with increased risk of colorectal cancer, but epidemiologic evidence for
fat and colorectal cancer is not as strong as judged by Boyle and Langman.
They referred in detail to the results in the Nurses' Health Study
published by Willett et al in 1990.1 It is a single prospective study
that showed an increased risk of colon cancer associated with high intake
of total or animal fat after adjustment for total calorie intake.
Epidemiological evidence should not be relied upon the result of a
single study, but the whole evidence must be considered. At least seven
large prospective studies have been reported in Europe and US until 1999,
and all of these studies have consistently failed to find a clear,
positive association between fat and colon or colorectal cancer; reported
relative risks for the highest versus lowest intake ranged 0.5 to 1.2 with
adjustment for total calorie. Six of these studies also addressed the
relation between saturated fat and colorectal cancer and found no material
association with relative risks of 0.7-1.4 for the highest versus lowest
intake. The Willett's group noted that the increased risk associated with
animal fat intake in the American nurses disappeared when red meat intake
was taken into account.2 Further, in the combined analysis of 13 case-
control studies, Howe et al showed no measurable positive association
between either total or saturated fat and colon cancer with adjustment for
total calorie intake.3 While animal studies have suggested an etiological
role for high fat intake in colorectal carcinogenesis, such evidence is
very hard to extrapolate to humans living freely.
Boyle and Langman also suggest that both vegetables and fruits may be
protective against colorectal cancer. However, little evidence exists
regarding the protective effect of fruits against colorectal cancer;
readers will relish a more accurate and succinct review article regarding
dietary factors and colorectal cancer,4 which Boyle and Langman missed in
the list of further readings.
Competing interests: None declared.
Suminori Kono professor of preventive medicine
Kyushu University Faculty of Medicine, Fukuoka 812-8582, Japan
1 Willett WC, Stampfer MJ, Colditz GA, Rosner BA, Speizer FE.
Relation of meat, fat, and fiber intake to the risk of colon cancer in a
prospective study among women. N Engl J Med 1990; 323:1664-72.
2 Giovannucci E, Rim EB, Stampfer MJ, Colditz GA, Ascherio A,
Willett WC. Intake of fat, meat, and fiber in relation to risk of colon
cancer in men. Cancer Res 1994; 54:2390-7.
3 Howe GR, Aronson KJ, Benito E, Castelleto R, Cornee J, Duffy S, et
al. The relationship between dietary fat intake and risk of colorectal
cancer: evidence from the combined analysis of 13 case-control studies.
Cancer Causes Control 1997; 8:215-28.
4 World Cancer Research Fund and American Institute for Cancer
Research. Food, nutrtion and the prevention of cancer: a global
perspective. Washington, DC: American Institute for Cancer Research, 1997.
Boyle and Langman's articel on epidemiology of colorectal cancer was
very useful and informative; I have a small query. The text on racial
differences states that for ethnic Japanese migrating to the USA risk
increases to 3-4 times higher than Japanese in Japan. Next to the text a
table of highest incidences of cancer quote figures of 53 per 100,000 for
Hawaiin Japanese, and 50 per 100,000 for Japanese in Hiroshima. I'd be
grateful if the apparent discrepancy between text and table coulc be
explained
Epidemiology of colorectal cancer
Editor - Boyle and Langman excellently summarized descriptive
features and risk factors of colorectal cancer in the ABC series of BMJ
(30 September 2000). However, it seems that the authors are rather
selective (or not well informed) of recent literature regarding dietary
and nutritional factors in the etiology of colorectal cancer. Boyle and
Langman states that intake of dietary fat and meat is positively related
to risk of colorectal cancer. High intake of meat is probably associated
with increased risk of colorectal cancer, but epidemiologic evidence for
fat and colorectal cancer is not as strong as judged by Boyle and Langman.
They referred in detail to the results in the Nurses' Health Study
published by Willett et al in 1990.1 It is a single prospective study
that showed an increased risk of colon cancer associated with high intake
of total or animal fat after adjustment for total calorie intake.
Epidemiological evidence should not be relied upon the result of a
single study, but the whole evidence must be considered. At least seven
large prospective studies have been reported in Europe and US until 1999,
and all of these studies have consistently failed to find a clear,
positive association between fat and colon or colorectal cancer; reported
relative risks for the highest versus lowest intake ranged 0.5 to 1.2 with
adjustment for total calorie. Six of these studies also addressed the
relation between saturated fat and colorectal cancer and found no material
association with relative risks of 0.7-1.4 for the highest versus lowest
intake. The Willett's group noted that the increased risk associated with
animal fat intake in the American nurses disappeared when red meat intake
was taken into account.2 Further, in the combined analysis of 13 case-
control studies, Howe et al showed no measurable positive association
between either total or saturated fat and colon cancer with adjustment for
total calorie intake.3 While animal studies have suggested an etiological
role for high fat intake in colorectal carcinogenesis, such evidence is
very hard to extrapolate to humans living freely.
Boyle and Langman also suggest that both vegetables and fruits may be
protective against colorectal cancer. However, little evidence exists
regarding the protective effect of fruits against colorectal cancer;
readers will relish a more accurate and succinct review article regarding
dietary factors and colorectal cancer,4 which Boyle and Langman missed in
the list of further readings.
Competing interests: None declared.
Suminori Kono
professor of preventive medicine
Kyushu University Faculty of Medicine, Fukuoka 812-8582, Japan
1 Willett WC, Stampfer MJ, Colditz GA, Rosner BA, Speizer FE.
Relation of meat, fat, and fiber intake to the risk of colon cancer in a
prospective study among women. N Engl J Med 1990; 323:1664-72.
2 Giovannucci E, Rim EB, Stampfer MJ, Colditz GA, Ascherio A,
Willett WC. Intake of fat, meat, and fiber in relation to risk of colon
cancer in men. Cancer Res 1994; 54:2390-7.
3 Howe GR, Aronson KJ, Benito E, Castelleto R, Cornee J, Duffy S, et
al. The relationship between dietary fat intake and risk of colorectal
cancer: evidence from the combined analysis of 13 case-control studies.
Cancer Causes Control 1997; 8:215-28.
4 World Cancer Research Fund and American Institute for Cancer
Research. Food, nutrtion and the prevention of cancer: a global
perspective. Washington, DC: American Institute for Cancer Research, 1997.
Competing interests: No competing interests