Diet and colorectal cancer: an investigation of the lectin/galactose hypothesis.
OBJECTIVE
Mucosal expression of terminal unsubstituted galactose is increased in colon cancer and precancer and allows interaction with mitogenic galactose-binding lectins of dietary or microbial origin. This study tests the hypothesis that galactose, which is variably plentiful in fruit and vegetable but not cereal fibers, might prevent cancer by binding and inhibiting such lectins.


METHODS
Colorectal cancer cases (512) and controls (512) were matched for age, sex, primary care practitioner, and postal code. A 160-item food-frequency questionnaire was used to estimate their usual pre-illness (6 months previous) diet, aspirin intake, and exercise.


RESULTS
Neither cereal fiber nor fruit and vegetable fiber were protective when assessed by univariate analysis, whereas dietary fiber galactose content showed a dose-related protective effect (odds ratio [OR] highest quartile/lowest quartile, 0.67; confidence interval [CI], 0.47-0.95) that remained protective when adjusted for energy, red meat, alcohol, calcium, protein and fat intake, regular aspirin usage, and exercise. Intake of nonlegume green vegetables, assessed because of the high lectin content of legumes, was also protective (OR, 0.54; CI, 0.35-0.81), but this was not independent of galactose. Protective effects of exercise and regular daily aspirin consumption and harmful effects of high energy consumption and high red meat intake were confirmed.


CONCLUSIONS
The protective effect of fruit and vegetable fibers may be related to their galactose content. This provides further evidence that the association between diet and colon cancer is mediated via specific food components and may explain the discrepant results of studies addressing the protective effects of fiber.
Evans
Richard C
RC
Department of Medicine, University of Liverpool, England.
Fear
Simon
S
Ashby
Deborah
D
Hackett
Alan
A
Williams
Evelyn
E
Van Der Vliet
Martine
M
Dunstan
Frank D J
FD
Rhodes
Jonathan M
JM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001241:Aspirin / Q000008:administration & dosage / Q000627:therapeutic use; D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000209:etiology / Q000517:prevention & control*; D004032:Diet; D004334:Drug Administration Schedule; D002149:Energy Intake; D015444:Exercise; D005260:Female; D005690:Galactose / Q000494:pharmacology*; D006801:Humans; D037102:Lectins / Q000494:pharmacology*; D008297:Male; D008460:Meat; D008875:Middle Aged; D015999:Multivariate Analysis; D012307:Risk Factors; D011795:Surveys and Questionnaires
D037102:Lectins; D001241:Aspirin; D005690:Galactose