The joint association of eating frequency and diet quality with colorectal cancer risk in the Health Professionals Follow-up Study

Abstract

The results of most case-control studies have suggested a positive association between eating frequency and colorectal cancer risk. Because no prospective cohort studies have done so to date, the authors prospectively examined this association. In 1992, eating frequency was assessed in a cohort of 34,968 US men in the Health Professionals Follow-up Study. Cox proportional hazards regression models were used to estimate relative risks and 95% confidence intervals for various levels of eating frequency. Effect modifications by overall dietary quality (assessed using the Diet Approaches to Stop Hypertension score) and by factors that influence insulin resistance were further assessed. Between 1992 and 2006, a total of 583 cases of colorectal cancer were diagnosed. When comparing the highest eating frequency category (5-8 times/day) with the reference category (3 times/day), the authors found no evidence of an increased risk of colorectal cancer (multivariate relative risk = 0.88, 95% confidence interval: 0.62, 1.26) or colon cancer (multivariate relative risk = 0.78, 95% confidence interval: 0.49, 1.25). There was an implied inverse association with eating frequency among participants who had healthier diets (high Diet Approaches to Stop Hypertension score; P for interaction = 0.01), especially among men in the high-insulin-sensitivity group (body mass index (weight (kg)/height (m)(2)) <25, ≥2 cups of coffee/day, and more physical activity; P for interaction < 0.01, P for trend = 0.01). There was an implied protective association between increased eating frequency of healthy meals and colorectal cancer risk and in men with factors associated with higher insulin sensitivity.

Figure 1.

Associations between colorectal cancer and other variables in 34,968 US men from the Health Professional Follow-up Study, 1992–2006. Values are hazard ratios from Cox proportional hazards models. All tests were 2-sided. A) Joint association between eating frequency and Dietary Approaches to Stop Hypertension (DASH) score and colorectal cancer risk (P for interaction = 0.01). Multivariate models were adjusted for age (in months), aspirin use (≥2 times per week, <2 times per week, or missing), family history of colorectal cancer (yes, no, or missing), previous endoscopy (screening in the past 2 years, never, or missing), use of supplements containing antioxidants (ever, never, or missing), body mass index (BMI, measured as weight (kg)/height (m)²; 24, 24–26.0, 26.1–29, or >29), energy intake (kilocalories/day, continuous), alcohol intake (0, 0.1–4.9, 5–14.9, or ≥15 g/day), physical activity level (quintile of metabolic equivalent hours/week), red meat consumption (quintile of servings/day), total calcium intake (quintile of mg/day), dietary folate intake (quintile of μg/day), dietary vitamin D intake (quintile of IU/day), pack years of smoking before 30 years of age (continuous or missing indicator), race (white, nonwhite, or missing), and DASH score (continuous) together with eating frequency (continuous). B) Joint association between eating frequency and physical activity level and colorectal cancer risk (P for interaction = 0.04). The same adjustments were made to the model as in A, except that physical activity level (median of deciles) was combined with eating frequency (continuous). C) Joint association between eating frequency and BMI with colorectal cancer risk (P for interaction = 0.07). The same adjustments were made to the model as in A, except that BMI (median of deciles) was combined with eating frequency (continuous). D) Joint association between eating frequency and insulin resistance score and colorectal cancer risk (P for interaction < 0.01). The same adjustments were made to the model as in A, except that physical activity level and BMI were omitted. The insulin sensitivity score consisted of the 3 combined variables (coffee intake, physical activity level, and BMI) and was categorized into 2 groups (0–1 vs. 2–3), such that a higher score denoted less insulin sensitivity (i.e., a relatively insulin-sensitive individual would get the highest score of 3 and an insulin-resistant person would get the worst score of 0). Bars and numbers in parentheses, 95% confidence intervals.