Vitamin A Intake and Risk of Incident, Sporadic Colorectal Adenoma Open Access

Abstract

Background: Colorectal cancer is the third leading cause of cancer incidence and mortality among both men and women in the United States. Colorectal cancer risk is modifiable, and dietary exposures are among the known risk factors for colorectal cancer. Vitamin A is an antioxidant, and has been shown to improve immune function. However, little is known about its association with colorectal adenoma, a precursor to colorectal carcinoma, in humans.

Methods: We examined the association between intakes of total and dietary vitamin A, including its two forms (retinol and carotene), with incident, sporadic colorectal adenoma in a case-control study of colorectal polyps conducted in Minnesota between 1991 and 1994). Individuals with no prior history of colorectal neoplasms completed comprehensive questionnaires prior to elective, outpatient endoscopy; of these patients, 564 colorectal adenoma cases, and 1,202 endoscopy-negative controls were identified. An additional group of 535 community controls frequency matched on age and sex was also included. The food frequency questionnaire (FFQ) was used to assess each participant's nutrient intakes. Logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CI) for associations of total and dietary intakes of vitamin A, and its major subtypes, retinol and carotene with colorectal adenoma.

Results:Dietary and total intakes of vitamin A, and total carotene intake were not statistically significantly associated with colorectal adenoma risk. The multivariable-adjusted ORs for incremental increases in total intake were OR = 0.97 (95% CI: 0.86-1.10) for total vitamin A (9561.56 IU/day), OR = 0.95 (95% CI: 0.87-1.05) for dietary vitamin A (7425.64 IU/day), OR = 1.03 (95% CI: 0.92-1.15) for total carotene (7425.64 IU/day), when comparing cases with all controls combined. There was, however, a significant inverse association, in the multivariable-adjusted model, with colorectal adenoma per 1 SD (SD = 3739.54 IU/day) increment in retinol (OR = 0.86, 95% CI: 0.75-0.98) when comparing cases with all controls combined. Associations did not vary substantially by sex, age, aspirin or NSAID use, or BMI.

Conclusion: These results suggest a possible inverse association between retinol, but not carotene, or total or dietary vitamin A, intakes and incident, sporadic colorectal adenoma.

Table of Contents

Background.........................................................................................1

Methods..............................................................................................9

Results...............................................................................................13

Discussion..........................................................................................17

Future Directions................................................................................20

References..........................................................................................21

Table 1...............................................................................................25

Table 2...............................................................................................28

Table 3...............................................................................................31

Table 4...............................................................................................34

Table 5...............................................................................................37

Table 6...............................................................................................40

About this Master's Thesis

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School	Rollins School of Public Health
Department	Epidemiology
Degree	MPH
Submission	Master's Thesis
Language	English
Research Field	Health Sciences, Public Health Health Sciences, Epidemiology
Keyword	Vitamin A Colorectal Adenoma
Committee Chair / Thesis Advisor	Fedirko, Veronika, Emory University

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