The association of glycemic load and carbohydrate intake with colorectal cancer risk in the Multiethnic Cohort Study.
BACKGROUND
High-glycemic-load diets may increase colorectal cancer risk through hyperinsulinemic effects.


OBJECTIVE
We analyzed data for 191,004 participants in the Multiethnic Cohort Study to determine the risk of colorectal cancer associated with glycemic load (GL), carbohydrate, and sucrose and to ascertain whether this risk was modified by sex and ethnicity.


METHODS
During 8 y of follow-up, 2379 incident cases of colorectal adenocarcinoma occurred. We used baseline quantitative food-frequency questionnaire data to assess usual dietary intake over the preceding year. Using Cox regression, we calculated adjusted relative risks (RRs) and 95% CIs for colorectal cancer associated with quintiles of GL, carbohydrate, and sucrose.


RESULTS
For both men and women in this cohort, white rice was the major contributor to GL. In multivariate models, RRs for colorectal cancer decreased significantly with increasing GL in women (RR for the highest quintile versus the lowest: 0.75; 95% CI: 0.57, 0.97; P for trend = 0.02) but not in men (RR: 1.15; 95% CI: 0.89, 1.48; P for trend = 0.19). Results for carbohydrate and sucrose were similar. The inverse association with GL was found in women of all ethnic groups (P for interaction = 0.58). In men, an interaction was found between ethnicity and GL (P < 0.01): white men had a positive association with increasing GL (RR: 1.69; 95% CI: 0.98, 2.92; P for trend < 0.01), but men of other ethnic groups did not.


CONCLUSIONS
GL and carbohydrate intake appear to protect against colorectal cancer in women in the Multiethnic Cohort, perhaps because a major source of GL is white rice.
Howarth
Nancy C
NC
Cancer Epidemiology Program, Cancer Research Center of Hawai'i, University of Hawai'i, Honolulu, HI 96813, USA.
Murphy
Suzanne P
SP
Wilkens
Lynne R
LR
Henderson
Brian E
BE
Kolonel
Laurence N
LN
D000230:Adenocarcinoma / Q000453:epidemiology* / Q000208:ethnology / Q000209:etiology / Q000517:prevention & control; D018256:Adenomatous Polyps / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology / Q000517:prevention & control; D000368:Aged; D015331:Cohort Studies; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000208:ethnology / Q000209:etiology / Q000517:prevention & control; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000145:classification / Q000378:metabolism; D019422:Dietary Sucrose / Q000008:administration & dosage* / Q000145:classification / Q000378:metabolism; D005006:Ethnicity; D005247:Feeding Behavior; D005260:Female; D038321:Glycemic Index; D006801:Humans; D006946:Hyperinsulinism / Q000150:complications / Q000209:etiology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016016:Proportional Hazards Models; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology
D004040:Dietary Carbohydrates; D019422:Dietary Sucrose