A comparison of prospective and retrospective assessments of diet in a study of colorectal cancer

A Prospective Analysis of Red and Processed Meat Intake in Relation to Colorectal Cancer in the Black Women's Health Study

BACKGROUND

Black Americans have the highest incidence of colorectal cancer (CRC) of any racial/ethnic group in the United States. High intake of red and processed meats has been associated with an increased CRC risk in predominately White populations. However, 3 prior studies in Black populations, who have been reported to have high intakes of red and processed meats, have reported no associations. Data on a possible association between CRC risk and SFAs and MUFAs, the primary types of fat in red and processed meats, are inconclusive.

OBJECTIVES

We prospectively assessed intakes of processed and unprocessed red meat, SFAs, and MUFAs in relation to CRC risk, utilizing data from the Black Women's Health Study (BWHS, 1995-2018).

METHODS

Dietary data were derived from validated FFQs completed in 1995 and 2001. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards regression.

RESULTS

Among 52,695 BWHS participants aged 21-69 y at baseline and followed for ≤22 y, 564 women developed incident CRC. Unprocessed red meat intake was associated with a 33% increased CRC risk per 100 g/d (HR: 1.33; 95% CI: 1.03-1.71). Examination of CRC anatomic sites revealed that unprocessed red meat was associated with 2-times increased rectal cancer risk (HR: 2.22; 95% CI: 1.15-4.26). There was no evidence of an interaction with age (pinteraction = 0.4), but unprocessed red meat intake was only associated with a significant increased risk of late-onset CRC (≥50 y of age, HR: 1.41; 95% CI: 1.05-1.88). Processed red meat and total SFA and MUFA intakes were not associated with CRC risk.

CONCLUSIONS

Unprocessed red meat intake was associated with an increased CRC risk in the present study, the first positive evidence that red meat plays a role in the etiology of CRC in Black women. The findings suggest prevention opportunities.

Nutrients, foods, and colorectal cancer prevention

Diet has an important role in the development of colorectal cancer. In the past few decades, findings from extensive epidemiologic and experimental investigations have linked consumption of several foods and nutrients to the risk of colorectal neoplasia. Calcium, fiber, milk, and whole grains have been associated with a lower risk of colorectal cancer, and red meat and processed meat have been associated with an increased risk. There is substantial evidence for the potential chemopreventive effects of vitamin D, folate, fruits, and vegetables. Nutrients and foods also may interact, as a dietary pattern, to influence colorectal cancer risk. Diet likely influences colorectal carcinogenesis through several interacting mechanisms. These include the direct effects on immune responsiveness and inflammation, and the indirect effects of overnutrition and obesity-risk factors for colorectal cancer. Emerging evidence also implicates the gut microbiota as an important effector in the relationship between diet and cancer. Dietary modification therefore has the promise of reducing colorectal cancer incidence.

Short- and long-term reliability of adult recall of vegetarian dietary patterns in the Adventist Health Study-2 (AHS-2)

Past dietary patterns may be more important than recent dietary patterns in the aetiology of chronic diseases because of the long latency in their development. We developed an instrument to recall vegetarian dietary patterns during the lifetime and examined its reliability of recall over 5·3 and 32·6 years on average. The short-term/5-year recall ability study (5-RAS) was done using 24 690 participants from the cohort of the Adventist Health Study-2 (mean age 62·2 years). The long-term/33-year recall ability study (33-RAS) included an overlap population of 1721 individuals who joined the Adventist Health Study-1 and Adventist Health Study-2 (mean age 72·5 years). Spearman correlation coefficients for recall of vegetarian status were 0·78 and 0·72 for the 5-RAS and 33-RAS, respectively, when compared with 'reference' data. For both time periods sensitivity and positive predictive values were highest for the lacto-ovo-vegetarian and non-vegetarian patterns (vegans, lacto-ovo-vegetarians, pesco-vegetarians, semi-vegetarians and non-vegetarians). In the 5-RAS analyses, male, non-black, younger, and more educated participants, lifetime Adventists, and those with more stability of consumption of animal products generally showed higher recall ability. Somewhat similar tendencies were shown for the 33-RAS analyses. Our findings show that the instrument has higher reliability for recalled lacto-ovo-vegetarian and non-vegetarian than for vegan, semi- and pesco-vegetarian dietary patterns in both short- and long-term recalls. This is in part because these last dietary patterns were greatly contaminated by recalls that correctly would have belonged in the adjoining category that consumed more animal products.

Fruit and vegetable consumption and the risk of proximal colon, distal colon, and rectal cancers in a case-control study in Western Australia

BACKGROUND

Fruits and vegetables (F/V) have been examined extensively in nutrition research in relation to colorectal cancer (CRC). However, their protective effect is subject to debate, possibly because of different effects on different subsites of the large bowel.

OBJECTIVE

To determine whether any association between F/V consumption and risk of CRC differed by subsite of the bowel (proximal colon, distal colon, and rectum).

DESIGN

The Western Australian Bowel Health Study is a population-based, case-control study conducted between June 2005 and August 2007. Complete food frequency questionnaire data were analysed from 834 CRC cases and 939 controls. Logistic regression analysis was used to estimate the effects of quartiles of F/V intake on risk of CRC at different subsites. Odds ratios (OR) and 95% confidence intervals (CI) were calculated for CRC overall and for the three separate subsites.

RESULTS

Risk of proximal colon cancer and rectal cancer was not associated with intakes of total F/V, total vegetable, or total fruit. Brassica vegetable intake was inversely related with proximal colon cancer (Q4 vs Q1 OR 0.62; 95% CI 0.41 to 0.93). For distal colon cancer, significant negative trends were seen for total F/V, and total vegetable intake. Distal colon cancer risk was significantly decreased for intake of dark yellow vegetables (Q4 vs Q1 OR 0.61; 95% CI 0.41 to 0.92) and apples (Q4 vs Q1 OR 0.51; 95% CI 0.34 to 0.77). An increased risk for CRC was found to be associated with intake of fruit juice (Q4 vs Q1 OR 1.74; 95% CI 1.24 to 2.45).

CONCLUSIONS

Our results suggest that different F/V may confer different risks for cancer of the proximal colon, distal colon, or rectum. Future studies might consider taking into account the location of the tumor when examining the relation between F/V consumption and risk of CRC.

Colorectal cancer chemoprevention--an overview of the science

The development and dissemination of sophisticated detection technologies have recently exposed the high prevalence of preinvasive colorectal neoplasia in the adult U.S. population. Although cancer screening and surveillance provide opportunities for risk stratification, they achieve risk reduction only when coupled with effective interventions. This review surveys the lead compounds for colorectal cancer prevention and the measures by which they may be prioritized for clinical testing. Clinical trials remain the rate-limiting step in agent development, and novel trial designs are needed to hasten agent identification and testing for cancer prevention. Innovative research models include the nesting of prevention end points within cancer treatment trials and within trials testing promising preventive compounds intended for nononcologic indications.

Prospective study on milk products, calcium and cancers of the colon and rectum

OBJECTIVE

To study the relationship between consumption of milk and milk products, calcium, lactose and vitamin D and occurrence of colorectal cancers.

DESIGN

Prospective cohort study.

SUBJECTS

A total of 9959 men and women aged 15 y or older without history of cancer at baseline. During a 24 y follow-up, 72 new cancers of the large bowel (38 in the colon and 34 in the rectum) were detected.

RESULTS

Consumption of milk and total milk products was suggested to be inversely related to colon cancer incidence, whereas no similar association was seen for rectal cancer. The relative risk between the highest and lowest quartiles of intake adjusted for potential confounding factors was 0.46 (95% confidence interval 0.14-1.46, P for trend 0.09) for milk and 0.37 (95% CI=0.12-1.39, P for trend 0.06) for total milk products. Lactose intake showed a similar inverse relationship with colon cancer: the relative risk was 0.31 (95% CI=0.08-1.15, P for trend 0.03). Intake of vitamin D or total dietary calcium was not significantly related to colorectal cancer risk, whereas calcium provided by fermented milk products was associated with increased colorectal cancer incidence; in the highest quartile the multivariate adjusted relative risk for colorectal cancer was 2.07 (95% CI=1.00-4.28).

CONCLUSIONS

Our results indicate that individuals showing high consumption of milk have a potentially reduced risk of colon cancer; however, the association does not appear to be due to intake of calcium, vitamin D, or to specific effects of fermented milk.

SPONSORSHIP

This study was supported by a grant from the Swedish Cancer Foundation.