Association between meeting the WCRF/AICR cancer prevention recommendations and colorectal cancer incidence: results from the VITAL cohort

Abstract

Purpose

In 2007, the World Cancer Research Fund (WCRF) and American Institute for Cancer Research (AICR) published eight recommendations regarding body weight, physical activity, and dietary behaviors aimed at reducing cancer incidence worldwide. In this paper, we assess whether meeting the WCRF/AICR recommendations is associated with lower colorectal cancer (CRC) incidence; evaluate whether particular recommendations are most strongly associated with lower CRC incidence; and assess whether associations differ by sex.

Methods

We operationalized six of the recommendations (related to body weight, physical activity, energy density, plant foods, red and processed meat, and alcohol) and examined their association with CRC incidence over 7.6 years of follow-up in the prospective VITamins And Lifestyle Study cohort. Participants included 66,920 adults aged 50–76 years at baseline (2000–2002) with no history of CRC and with complete data for the recommendations evaluated. Incident colorectal cancers (n = 546) were tracked through 2009.

Results

Compared with meeting no recommendations, meeting 1–3 recommendations was associated with 34–45 % lower CRC incidence, and meeting 4–6 was associated with 58 % lower incidence (95 % CI 34 %, 74 %) in fully adjusted analyses. The recommendations most strongly associated with lower CRC risk for women were related to body fatness and red and processed meat, while for men these were alcohol intake and red and processed meat. Differences by sex were statistically significant (p < 0.05) for the recommendations related to body weight and to alcohol.

Conclusions

Meeting the WCRF/AICR recommendations, particularly those related to alcohol, body weight, and red and processed meat, could substantially reduce CRC incidence; however, associations differ by sex.

Appendix

In the Fall of 2011 we convened an expert panel of nutritional epidemiologists (Emily White, Alan Kristal, Ruth Patterson, Shirley Beresford) with knowledge of the VITAL cohort and the WCRF/AICR recommendations to determine the approach and appropriate cutoffs to be used when operationalizing these recommendations in the VITAL cohort. Decisions on how to operationalize each recommendation were made by first attempting to define adherence using the “Personal Recommendations,” with additional information from the “Public Health Goals” and included references used to determine cutoffs when the personal recommendations were not specific. When the personal recommendations included clear targets, those values were used. The expert panel also decided that the overall analysis approach would treat each recommendation as either being met or not met and that we would not include partial adherence points for the recommendations.

Recommendation 1: body fatness

We set cutoffs of body mass index at baseline of between 18.5 and <25.0 kg/m² to be consistent with the personal recommendation to “maintain body weight within the normal range from age 21” with a reference to ranges issued by national governments or the World Health Organization (whose cutoffs we used). We opted not to incorporate the additional personal recommendations related to childhood and adolescent body weight and about avoiding weight gain and increases in waist circumference throughout adulthood because the child and adolescent body weight and waist circumference data were not available and, although participant reports of body weight at ages 18, 30, and 45 were available, there were several missing responses, and we were concerned about the accuracy of the provided estimates.

Recommendation 2: physical activity

We utilized the detailed physical activity questionnaire in VITAL, incorporating walking and other moderate and strenuous activities and their frequency and duration over the previous 10 years, to set cutoffs to identify participants meeting the personal recommendation to “be moderately physically active, equivalent to brisk walking for at least 30 min every day.” We ultimately counted participants reporting walking at a moderate or fast (but not casual) pace and/or participating in moderate or strenuous activities (such as running, aerobics, dancing, swimming, cycling, or sports) but not mild exercise (such as golf, slow dancing, or bowling) for an average of at least 30 min per day on an average of at least 5 days per week over at least 7 of the previous 10 years. The personal recommendation to aim for 60 min of moderate or 30 min of vigorous activity every day as fitness improves was not incorporated because data on changes in fitness and activity over time were not available; however, we did capture long-term physical activity patterns by incorporating data from the previous 10 years. The personal recommendation to limit sedentary habits such as watching television was not incorporated because data on sedentary time were not available.

Recommendation 3: foods and drinks that promote weight gain

The personal recommendations to “consume energy-dense foods sparingly,” “avoid sugary drinks,” and “consume ‘fast foods’ sparingly, if at all” did not provide clear cut-points for what constituted meeting this recommendation. The VITAL food frequency questionnaire (FFQ) captures detailed information on beverages and also captures total calories consumed and the average weight in grams of each of the included individual foods and mixed dishes, but does not specifically ask about “fast foods.” We utilized additional information from the associated public health goals that the average energy density of the diets should be lowered to 125 kcal per 100 g to establish our cutoff for dietary energy density of foods consumed. This cutoff excluded beverages, so we further required that participants also consume less than one serving of regular (not diet) soda, fruit drinks, or cranberry juice with added sugar each week. The additional requirement that participants consume fewer than 3 servings of other fruit juices (e.g., orange juice) per week was added in response to suggestions received through peer review of these recommendations.

Recommendation 4: plant foods

The personal recommendations related to plant foods included eating at least 5 portions of fruits and non-starchy vegetables every day, relatively unprocessed grains and/or legumes with every meal, and limiting refined starches. The expert panel decided that participants would be counted as meeting this recommendation if they consumed at least 5 servings per day of fruits and non-starchy vegetables (fruit juices and white potatoes did not count toward meeting the recommendation) and also consumed at least one serving per day of whole grains or legumes. The VITAL FFQ was not developed to capture whole grains separately from refined grains, so this lower threshold was selected to capture regular consumption of these foods rather than requiring the consumption of at least one serving per meal. An additional personal recommendation that individuals who consume starchy roots or tubers as staples also ensure sufficient intake of non-starchy vegetables, fruits, and legumes was not addressed because this dietary pattern is not common in the USA.

Recommendation 5: animal foods

The expert panel decided to follow the personal recommendation that “people who eat red meat to consume less than 500 g (18 oz) a week, very little, if any to be processed” and count participants as meeting this recommendation if they consumed fewer than 18 oz of red or processed meat (reported as individual foods or mixed dishes such as pasta with meat sauce) per week. The additional requirement that participants consume no more than one serving per week of processed meat was added in response to suggestions received through peer review of these recommendations.

Recommendation 6: alcohol

The expert panel followed the personal recommendation that alcohol consumption should be limited to no more than one drink per day for women and no more than two per day for men, where a drink contains between 10 and 15 g of ethanol.

Recommendation 7: preservation, processing, preparation

The expert panel chose not to operationalize the personal recommendations to avoid salt-preserved foods and to not eat moldy grains or legumes because these practices are not common in the USA and appropriate data are not captured in the VITAL FFQ. The panel further decided not to include the recommendation to limit consumption of processed foods and limit intake to less than 2.4 g sodium per day because the validity of sodium measurement using FFQs has not been established.

Recommendation 8: dietary supplements

The personal recommendation that “dietary supplements are not recommended for cancer prevention” was not operationalized. While the public health goal is to increase the proportion of the population meeting nutritional needs through diet, rather than supplements, the WCRF/AICR also cites studies that have suggested that supplements may reduce cancer risk in certain high-risk groups and declines to make a population-wide recommendation on whether to take or avoid supplements.