Dietary glycemic index, glycemic load, and risk of incident breast cancer in postmenopausal women.

Insulin and insulin-like growth factor-I (IGF-I) are associated with increased risk of breast cancer in several studies. Circulating concentrations of insulin increase with dietary consumption of high glycemic index foods, which, in turn, may influence IGF-I levels or activity, but the relevance of such dietary patterns for breast cancer risk is unclear. We investigated whether consumption of carbohydrates with high dietary glycemic index would predict risk of postmenopausal breast cancer among 63,307 United States women in the Cancer Prevention Study II Nutrition Cohort. From baseline in 1992, participants 40-87 years of age and free from cancer and diabetes, were followed for 5 years; 1442 incident breast cancer cases were documented. Diet was assessed at baseline by a validated 68-item food frequency questionnaire from which we calculated dietary glycemic index and glycemic load. Dietary glycemic index and load were not associated with increased risk of postmenopausal breast cancer (rate ratio = 1.03; 95% confidence interval, 0.87-1.22 and rate ratio = 0.90; 95% confidence interval, 0.76-1.08, respectively) after adjustment for multiple breast cancer risk factors. Associations were not modified by body mass index, physical activity, hormone use, or stage of disease. Future evaluations of glycemic index and breast cancer risk may be strengthened by longer follow-up, more complete dietary information, and measurement of plasma insulin and IGF-I levels.     

Dietary carbohydrates and breast cancer risk: a prospective study of the roles of overall glycemic index and glycemic load

We examined breast cancer risk in association with overall glycemic index (GI), glycemic load (GL), and dietary carbohydrate and sugar intake in a prospective cohort of 49,613 Canadian women enrolled in the National Breast Screening Study who completed a self-administered food frequency questionnaire between 1980 and 1985. Linkages to national mortality and cancer databases yielded data on deaths and cancer incidence, with follow-up ending between 1998 and 2000. During a mean follow-up of 16.6 years, we observed 1,461 incident breast cancer cases. GI, GL, total carbohydrate and total sugar intake were not associated with breast cancer risk in the total cohort. However, there was evidence of effect modification of the association between GI and breast cancer risk by menopausal status (p = 0.01), the hazard ratio for the highest versus the lowest quintile level of GI being 0.78 (95% CI = 0.52-1.16; ptrend = 0.12) in premenopausal women and 1.87 (95% CI = 1.18-2.97; ptrend = 0.01) in postmenopausal women. The associations between GI and GL were not modified by body mass index (BMI) or by vigorous physical activity among pre- or postmenopausal women. Similarly, the associations between GI/GL and risk in postmenopausal women were not modified by BMI, vigorous physical activity, or ever use of hormone replacement therapy (HRT), although the associations were slightly stronger among those who reported no vigorous physical activity (ptrend = 0.02), among those who reported ever using HRT (ptrend = 0.02) and among normal-weight women (BMI < 25 kg/m2; ptrend = 0.03). Our data suggest that consumption of diets with high GI values may be associated with increased risk of breast cancer among postmenopausal women, possibly more so among subgroups defined by participation in vigorous physical activity, ever use of HRT and those who are not overweight.     

Dietary glycemic load, carbohydrate, sugar, and colorectal cancer risk in men and women.

Hyperinsulinemia may explain excess colorectal cancer among individuals who are overweight or inactive. Recent studies have observed elevated colorectal cancer risk among individuals with elevated insulin levels 2 hours after oral glucose challenge or with elevated plasma C-peptide levels. The effect of consuming a high glycemic diet on colorectal risk, however, remains uncertain. Two prospective cohort studies, the Nurses' Health Study and the Health Professionals Follow-up Study, contributed up to 20 years of follow-up. After exclusions, 1,809 incident colorectal cancers were available for analyses. Dietary glycemic load (GL) was calculated as a function of glycemic index (postprandial blood glucose response as compared with a reference food), carbohydrate content, and frequency of intake of individual foods reported on food frequency questionnaires. Multivariable Cox proportional hazards models were used to adjust for potential confounders. Intakes of dietary carbohydrate, GL, overall glycemic index, sucrose, and fructose were not associated with colorectal cancer risk in women. A small increase in risk was observed in men with high dietary GL (multivariate relative risk, 1.32; 95% confidence interval, 0.98-1.79; highest versus lowest quintile), sucrose or fructose (multivariate relative risk, 1.37; 95% confidence interval, 1.05-1.78; highest versus lowest quintile of fructose, P = 0.008). Associations were slightly stronger among men with elevated body mass index (> or =25 kg/m(2)). Results among women were similar after stratifying by body mass index or physical activity. High intakes of GL, fructose, and sucrose were related to an elevated colorectal cancer risk among men. For women, however, these factors did not seem to increase the risk of colorectal cancer.     

Dietary glycemic index and glycemic load, and breast cancer risk: A case-control study

Background:Certain types of carbohydrates increase glucoseand insulin levels to a greater extent than others. In turn, insulin mayraise levels of insulin-like growth factors, which may influence breastcancer risk. We analyzed the effect of type and amount of carbohydrateson breast cancer risk, using the glycemic index and the glycemic loadmeasures in a large case-control study conducted in Italy. Patients and methods:Cases were 2569 women with incident,histologically-confirmed breast cancer interviewed between 1991 and1994. Controls were 2588 women admitted to the same hospital network fora variety of acute, non-neoplastic conditions. Average daily glycemicindex and glycemic load were calculated from a validated 78-item foodfrequency questionnaire. Results:Direct associationswith breast cancer risk emerged for glycemic index (odds ratio, OR forhighest vs. lowest quintile = 1.4; Pfor trend <0.01) andglycemic load (OR = 1.3; P< 0.01). High glycemic indexfoods, such as white bread, increased the risk of breast cancer (OR= 1.3) while the intake of pasta, a medium glycemic index food, seemedto have no influence (OR = 1.0). Findings were consistent acrossdifferent strata of menopausal status, alcohol intake, and physicalactivity level. Conclusions:This study supports thehypothesis of moderate, direct associations between glycemic index orglycemic load and breast cancer risk and, consequently, a possible roleof hyperinsulinemia/insulin resistance in breast cancer development.     

Dietary carbohydrate,glycemic index,and glycemic load and the risk of colorectal cancer in the BCDDP cohort

Background There is considerable support for associations between insulin and IGF-I levels and colorectal cancer. Diet may relate to colorectal cancer through this mechanism, for example, diets high in glycemic index, glycemic load and/or carbohydrate are hypothesized to increase insulin load and the risk of insulin resistance, hyperinsulinemia. Case–control studies support this hypothesis, but prospective cohorts have had mixed results. Methods In the Breast Cancer Detection Demonstration Project (BCDDP) follow-up cohort of 45,561 women, we used Cox proportional hazards regression to assess the distribution of 490 incident cases of colorectal cancer ascertained during 8.5 years of follow-up across quintiles of carbohydrate intake, glycemic index, and glycemic load. We also stratified by combined BMI and physical activity levels. Results We found reductions in colorectal cancer risk for diets high in carbohydrate (RR for Q5 vs. Q1 = 0.70, 95% CI: 0.50–0.97) and glycemic index (0.75, 95% CI: 0.56–1.00), and no significant association for glycemic load (0.91, 95% CI: 0.70–1.20). Inverse associations were weakest in normal weight active persons. The inverse association for glycemic index was strongest for the portion from dairy food. Conclusions These results do not support an association between diets high in carbohydrate, glycemic index or glycemic load and colorectal cancer.     

Dietary glycemic load, glycemic index and colorectal cancer risk: results from the Netherlands Cohort Study

Since hyperinsulinemia is implicated in the development of colorectal cancer, determinants of serum insulin levels, like the glycemic load and the glycemic index of the diet, could influence cancer risk. Our objective was to evaluate whether a diet with a high glycemic load or glycemic index is associated with increased colorectal cancer risk. In the Netherlands Cohort Study, 120,852 subjects completed a food frequency questionnaire in 1986. After 11.3 years of follow-up, 1,225 colon and 418 rectal cancer cases were available for analysis. A case-cohort approach was used to estimate multivariate adjusted rate ratios and 95% confidence intervals for quintiles of energy-adjusted glycemic load and glycemic index. The RR for colorectal cancer comparing the highest versus the lowest quintile levels of glycemic load and glycemic index were 0.83 (95% CI: 0.64-1.08) and 0.81 (95% CI: 0.61-1.08) for men and 1.00 (95% CI: 0.73-1.36) and 1.20 (95% CI: 0.85-1.67) for women. In general, no clear associations with cancer subsites were observed. Glycemic load and glycemic index were borderline significantly associated with an increased risk of proximal colon cancer in women (p-trend = 0.06 and 0.08, respectively), however, these associations were attenuated after exclusion of the first 2 years of follow-up (p-trend = 0.165 and 0.254, respectively). In men, glycemic index was associated with a reduced risk of distal colon cancer (p-trend = 0.03). Overall, our findings do not support the hypothesis that a diet with a high glycemic load or index is associated with a higher risk of colorectal cancer.     

Glycemic index,glycemic load and cancer risk

BackgroundDietary glycemic index (GI) and glycemic load (GL) have been related to the risk of selected cancers, but the issue remains open.Patients and methodsMailed questionnaires were completed between 1994 and 1997 in eight Canadian provinces for incident, histologically confirmed cases of the stomach (n = 1182), colon (n = 1727), rectum (n = 1447), liver (n = 309), pancreas (n = 628), lung (n = 3341), breast (n = 2362), ovary (n = 442), prostate (n = 1799), testis (n = 686), kidney (n = 1345), bladder (n = 1029), brain (n = 1009), non-Hodgkin's lymphomas (NHL, n = 1666), leukemias (n = 1069), multiple myelomas (n = 343), and 5039 population controls. Dietary information on eating habits 2 years before participants' enrollment in the study was obtained using a validated food frequency questionnaire (FFQ). Odds ratios (ORs) and 95% confidence intervals (CI) were derived by unconditional logistic regression including recognized confounding factors.ResultsDietary GI was positively associated with the risk of prostate cancer (OR, 1.26 for the highest versus the lowest quartile). A higher dietary GL significantly increased the risk of colorectal (OR, 1.28), rectal (OR, 1.44) and pancreatic (OR, 1.41) cancers. No other significant associations were found.ConclusionsOur findings suggest that a diet high in GI and GL is associated with increased risk of selected cancers.     

Dietary glycemic load and colorectal cancer risk

Background:Insulin and insulin-like growth factors can stimulateproliferation of colorectal cells. High intake of refined carbohydrates andmarkers of insulin resistance are associated with colorectal cancer. To testthe insulin/colon cancer hypothesis, we determined whether the dietaryglycemic index and the glycemic load are associated with colorectal cancerrisk. Design:A case-control study on colorectal cancer conducted inItaly. Cases included 1125 men and 828 women with histologically confirmedincident cancer of the colon or rectum. Controls were 2073 men and 2081 womenhospitalized for acute conditions. We calculated average daily dietaryglycemic index and glycemic load, and fiber intake from a validated foodfrequency questionnaire. Results:Direct associations with colorectal cancer risk emergedfor glycemic index (odds ratio (OR) in highest vs. lowest quintile = 1.7;95% confidence interval (CI): 1.4–2.0) and glycemic load (OR =1.8; 95% CI: 1.5–2.2), after allowance for sociodemographicfactors, physical activity, number of daily meals, and intakes of fiber,alcohol and energy. ORs were more elevated for cancer of the colon thanrectum. Overweight and low intake of fiber from vegetables and fruit appearedto amplify the adverse consequences of high glycemic load. Conclusions:The positive associations of glycemic index and loadwith colorectal cancer suggest a detrimental role of refined carbohydrates inthe etiology of the disease.     

Dietary glycemic index,glycemic load,and risk of breast cancer: meta-analysis of prospective cohort studies

Consumption diets of high glycemic index (GI) and glycemic load (GL) may increase the risk of breast cancer. We aimed to conduct a meta-analysis of prospective cohort studies to evaluate the associations between dietary GI and GL and risk of breast cancer. We searched the PubMed database for relevant studies through November 2010, with no restrictions. We included prospective cohort studies that reported relative risk (RR) with 95% confidence intervals (CIs) for the associations of dietary GI and GL with breast cancer risk. Summary RRs were calculated using both fixed- and random-effects models. We identified 10 prospective cohort studies eligible for analysis, involving 15,839 cases and 577,538 participants. The summary RR of breast cancer for the highest GI intake compared with the lowest was 1.08 (95% CI: 1.02–1.14), with no evidence of heterogeneity (P = 0.72, I ² = 0%). For GL, the summary RR was 1.04 (95% CI: 0.95–1.15), and substantial heterogeneity was observed (P = 0.02, I ² = 55.6%). The GI and GL and breast cancer associations did not significantly modified by geographic region, length of follow-up, number of cases, or menopausal status at baseline. Dose–response analysis was not performed due to limited number of eligible studies. There was no evidence of publication bias. In summary, the present meta-analysis of prospective cohort studies suggests that high dietary GI is associated with a significantly increased risk of breast cancer. However, there is no significant association between dietary GL and breast cancer risk.     

Dietary glycemic index,glycemic load,insulin index,fiber and whole-grain intake in relation to risk of prostate cancer

Objective  

Insulin may play a role in prostate cancer tumorigenesis. Postprandial blood glucose and insulin responses of foods depend importantly on the carbohydrate quality and quantity, represented by glycemic index (GI), glycemic load (GL), fiber and whole-grain content, but are also influenced by intake of protein and other characteristics. The recently developed insulin index (II) quantifies the postprandial insulin secretion, also taking into account these additional characteristics.     

Dietary glycemic index, glycemic load and ovarian cancer risk: a case-control study in Italy.

BACKGROUND: Dietary carbohydrates vary in their ability to raise blood glucose and insulin levels, which, in turn, influence levels of sex hormones and insulin-like growth factors. We analyzed the effect of type and amount of carbohydrates on ovarian cancer risk, using the glycemic index (GI) and the glycemic load (GL) measurement in a large case-control study conducted in Italy. MATERIALS AND METHODS: Cases included 1031 women with incident, histologically confirmed epithelial ovarian cancer, from four Italian regions. Controls included 2411 women admitted to the same hospital networks for acute, non-neoplastic conditions. Average daily GI and GL were calculated from a validated food frequency questionnaire. Odds ratios (OR) and the corresponding 95% confidence intervals (CI) were computed using multiple logistic regression. RESULTS: Ovarian cancer was directly associated with dietary GI (OR for highest versus lowest quartile = 1.7, 95% CI 1.3-2.1) and GL (OR = 1.7, 95% CI 1.3-2.1). The associations were observed in pre- and postmenopausal women, and they remained consistent across strata of major covariates identified. CONCLUSIONS: This study supports the hypothesis of a direct association between GI and GL and ovarian cancer risk and, consequently, of a possible role of hyperinsulinemia/insulin resistance in ovarian cancer development.     

Dietary glycemic index,glycemic load,and endometrial cancer risk: The Japan Public Health Center-based Prospective Study

Evidence supporting the association of glycemic index (GI) and glycemic load (GL) with the risk of endometrial cancer is controversial and reports from Asia were limited. Therefore, we aimed to investigate the association in Japanese women. We evaluated 52 460 women in the Japan Public Health Center-based Prospective Study aged 45-74 years who responded to the 5-year follow-up survey. GI and GL were calculated from a validated food frequency questionnaire, and the participants were divided into three groups by GI and GL. The hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated with the Cox proportional hazard model adjusted for potential confounding factors. As a result, within 15.5 years of follow-up, 166 new cases of endometrial cancer were identified. Compared with the lowest GI and GL tertile groups, the HR of the risk of endometrial cancer in the highest GI tertile group was 0.80 (95% CI, 0.53-1.20; P_trend = .33), and that of the highest GL tertile group was 0.79 (95% CI, 0.52-1.19; P_trend = .82). The results were unchanged after stratification by body mass index, coffee consumption, and history of diabetes. In conclusion, we did not find any significant association between GI and GL with the risk of endometrial cancer. Further research is required to clarify the association.     

Glycemic index, glycemic load and risk of prostate cancer

Dietary carbohydrates have different glycemic and insulinemic potentials depending on type (glycemic index, GI) and amount (glycemic load, GL) of carbohydrate consumed or both. Insulin in turn has been implicated as a risk factor for several cancers, including that of the prostate. We assessed the relationship of GI and GL with prostate cancer risk in a multicenter case-control study. Cases and controls were recruited between 1991 and 2002 in the network of major teaching and general hospitals in 4 Italian areas. Cases were 1,204 men (age range 46-74 years) admitted for incident, histologically confirmed prostate cancer. Controls were 1,352 men (age range 46-74 years) admitted for acute, nonmalignant conditions unrelated to long-term modifications of diet. ORs of prostate cancer and the corresponding 95% CIs were derived using unconditional multiple logistic regression, including terms for age, study center, education, family history of prostate cancer, smoking, body mass index, physical activity, alcohol consumption, intake of energy, fiber and lycopenes. Compared to the lowest quintile of GI, the ORs were 1.23, 1.24, 1.47 and 1.57 for subsequent levels of GI. The corresponding values for GL were 0.91, 1.00, 1.20 and 1.41. No heterogeneity was found among strata of selected covariates. We found direct relations between dietary GI and GL and prostate cancer risk. Correcting for potential confounding factors did not substantially modify these associations.     

Carbohydrate intake,glycemic load,glycemic index,and risk of ovarian cancer

BackgroundOur objective was to determine the relationship between dietary glycemic load (GL), glycemic index (GI), carbohydrate intake, and ovarian cancer risk in a population-based case–control study.Patients and methodsA self-administered questionnaire was used to collect data on demographic and lifestyle factors, and a food frequency questionnaire was used to collect dietary information from 1366 women with ovarian cancer and 1414 population controls.ResultsGL was positively associated with ovarian cancer. The adjusted odds ratio (OR) for the highest versus the lowest quartile of intake was 1.24 [95% confidence interval (CI) 1.00–1.55, P for trend = 0.03]. Fiber intake was inversely associated with risk. The OR comparing women in the highest fiber-intake group with those in the lowest was 0.78 (95% CI 0.62–0.98, P for trend = 0.11). We found no association between GI, carbohydrate intake, and ovarian cancer. In analyses stratified by body mass index, the risk estimates for GL, carbohydrate, and sugar were higher among overweight/obese women; however, the interaction term was only significant for sugar (P for interaction = 0.004).ConclusionsOur results suggest that diets with a high GL may increase the risk of ovarian cancer, particularly among overweight/obese women, and a high intake of fiber may provide modest protection.     

Glycemic index, glycemic load and thyroid cancer risk.

BACKGROUND: Risk of thyroid cancer has already been related to refined cereals and starch food, but the association has not been studied in terms of glycemic index (GI) and glycemic load (GL). PATIENTS AND METHODS: We analyzed data from a case-control study conducted in Italy from 1986 to 1992 and including 399 histologically confirmed and incident cases of thyroid cancer and 616 control subjects. Information on dietary habits was derived through a food-frequency questionnaire and multivariate odds ratios (ORs) for GI and GL levels were estimated with adjustment for age, education, sex, area of residence, history of diabetes, body mass index, smoking, alcohol consumption, intake of fruit and vegetables, and noncarbohydrate energy intake. RESULTS: Compared with the lowest tertile, the ORs in subsequent tertiles were 1.68 and 1.73 for GI, and 1.76 and 2.17 for GL. The OR for highest tertile of GI compared with lowest one was 1.70 for papillary and 1.57 for follicular thyroid cancer. The ORs for GL were 2.17 for papillary and 3.33 for follicular thyroid cancer. CONCLUSION: Our study shows that high dietary levels of GI and GL are associated with thyroid cancer risk.     

Glycemic index, glycemic load and risk of gastric cancer.

BACKGROUND: Dietary carbohydrates have been directly associated with gastric cancer risk and have been considered general indicators of a poor diet. However, elevated levels of glucose and insulin elicited by consumption of high amounts of refined carbohydrates may stimulate mitogenic and cancer-promoting insulin-like growth factors (IGF). Glycemic index (GI) and glycemic load (GL), which represent indirect measures of dietary insulin demand, were analysed to understand further the association between carbohydrates and gastric cancer. PATIENTS AND METHODS: Data were derived from a hospital-based case-control study on gastric cancer, conducted in Italy between 1985 and 1997, including 769 cases with incident, histologically confirmed gastric cancer and 2081 controls admitted to the same hospital network as cases for acute, non-neoplastic diseases. All subjects were interviewed using a reproducible food frequency questionnaire. RESULTS: The multivariate odds ratios (OR) for subsequent quartiles of dietary GL were 1.44 [95% confidence interval (CI) 1.11-1.87], 1.62 (95% CI 1.24-2.12) and 1.94 (95% CI 1.47-2.55). No consistent pattern of risk was seen with GI. The associations were consistent in different strata of age, education and body mass index, and were stronger in women. CONCLUSIONS: This study supports the hypothesis of a direct association between GL and gastric cancer risk, thus providing an innovative interpretation, linked to excess circulating insulin and related IGFs, for the association between carbohydrates and risk of gastric cancer.     

Dietary glycemic index and glycemic load and risk of colorectal cancer: results from the EPIC‐Italy study

A carbohydrate‐rich diet, resulting in high blood glucose and insulin, has been hypothesized as involved in colorectal cancer etiology. We investigated dietary glycemic index (GI) and glycemic load (GL), in relation to colorectal cancer, in the prospectively recruited EPIC‐Italy cohort. After a median 11.7 years, 421 colorectal cancers were diagnosed among 47,749 recruited adults. GI and GL were estimated from validated food frequency questionnaires. Multivariable Cox modeling estimated hazard ratios (HRs) for associations between colorectal cancer and intakes of total, high GI and low GI carbohydrate and GI and GL. The adjusted HR of colorectal cancer for highest versus lowest GI quartile was 1.35; 95% confidence interval (CI) 1.03–1.78; p trend 0.031. Increasing high GI carbohydrate intake was also significantly associated with increasing colorectal cancer risk (HR 1.45; 95% CI 1.04–2.03; p trend 0.034), whereas increasing low GI carbohydrate was associated with reducing risk (HR 0.73; 95% CI 0.54–0.98; p trend 0.033). High dietary GI and high GI carbohydrate were associated with increased risks of cancer at all colon sites (HR 1.37; 95% CI 1.00–1.88, HR 1.80; 95% CI 1.22–2.65, respectively), whereas high GI carbohydrate and high GL were associated with increased risk of proximal colon cancer (HR 1.94; 95% CI 1.18–3.16, HR 2.01; 95% CI 1.08–3.74, respectively). After stratification for waist‐to‐hip ratio (WHR), cancer was significantly associated with GI, and high GI carbohydrate, in those with high WHR. These findings suggest that high dietary GI and high carbohydrate intake from high GI foods are associated with increased risk of colorectal cancer.     

Dietary patterns and breast cancer risk among Chinese women

Objective

The present study aimed to examine the relationship between dietary patterns and breast cancer risk among Chinese women.

Methods

Four hundred and thirty-eight cases with histologically confirmed primary breast cancer and 438 controls were consecutively recruited. Cases were frequency matched to controls on 5-year age group and rural?Curban residence. A validated food frequency questionnaire was used to assess dietary intake by face-to-face interviews. Dietary patterns were identified by factor analysis. Multivariate odds ratios (OR) and 95% confidence interval (CI) were estimated using unconditional logistic regression adjusted for various potential confounders.

Results

Two diet patterns were identified: vegetable?Cfruit?Csoy?Cmilk?Cpoultry?Cfish pattern and refined grain?Cmeat?Cpickle pattern. After adjustment for confounders, a 74% decreased risk was observed among women in the highest quartile of the vegetable?Cfruit?Csoy?Cmilk?Cpoultry?Cfish dietary pattern relative to the lowest quartile (OR = 0.26, 95% CI = 0.17?C0.42). The refined grain?Cmeat?Cpickle pattern was positively associated with breast cancer risk (OR = 2.58, 95% CI = 1.53, 4.34). Women with a high intake of the vegetable?Cfruit?Csoy?Cmilk?Cpoultry?Cfish pattern and a low intake of the refined grain?Cmeat?Cpickle pattern showed a decreased risk of breast cancer (adjusted OR = 0.26, 95% CI = 0.17?C0.41).

Conclusions

These results indicated that a diet characterized by a high consumption of vegetable/fruit/soy/milk/poultry/fish and a low consumption of refined grain/red meat/pickle is associated with a lower risk of breast cancer in Chinese women.     

Glycemic load,glycemic index and breast cancer risk in a prospective cohort of Swedish women

High‐glycemic load diets have been hypothesized to increase the risk of breast cancer but epidemiologic studies have yielded inconsistent findings. We examined the associations of carbohydrate intake, glycemic index and glycemic load with risk of overall and hormone receptor‐defined breast cancer in the Swedish Mammography Cohort, a population‐based cohort of 61,433 women who completed a food frequency questionnaire at enrollment in 1987–1990. During a mean follow‐up of 17.4 years, we ascertained 2,952 incident cases of invasive breast cancer. Glycemic load but not carbohydrate intake or glycemic index was weakly positively associated with overall breast cancer risk (p for trend = 0.05). In analyses stratified by estrogen receptor (ER) and progesterone receptor (PR) status of the breast tumors, we observed statistically significant positive associations of carbohydrate intake, glycemic index and glycemic load with risk of ER+/PR? breast cancer; the multivariate relative risks comparing extreme quintiles were 1.34 [95% confidence interval (CI) = 0.93–1.94; p for trend = 0.04] for carbohydrate intake, 1.44 (95% CI = 1.06–1.97; p for trend = 0.01) for glycemic index and 1.81 (95% CI = 1.29–2.53; p for trend = 0.0008) for glycemic load. No associations were observed for ER+/PR+ or ER?/PR? breast tumors. These findings suggest that a high carbohydrate intake and diets with high glycemic index and glycemic load may increase the risk of developing ER+/PR? breast cancer. © 2009 UICC