Dietary fatty acids, luminal modifiers, and risk of colorectal cancer

IJC International Journal of Cancer

Dietary fatty acids, luminal modifiers, and risk of colorectal cancer Ikuko Kato1,2, Adhip P. Majumdar1,4,5, Susan J. Land1,3, Jill S. Barnholtz-Sloan6 and Richard K. Severson7 1

Karmanos Cancer Institute, Wayne State University School of Medicine, Detroit, Michigan, USA Department of Pathology, Wayne State University School of Medicine, Detroit, Michigan, USA 3 Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, Michigan, USA 4 Department of Internal Medicine, Wayne State University School of Medicine, Detroit, Michigan, USA 5 John D. Dingell Veterans Affair Medical Center, Detroit, Michigan, USA 6 Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio, USA 7 Department of Family Medicine and Public Health Sciences, Wayne State University School of Medicine, Detroit, Michigan, USA 2

Epidemiology

Inconsistent observations in epidemiologic studies on the association between total fat intake and colorectal cancer may be ascribed to opposing effects of individual fatty acids and the presence of other dietary constituents that modify luminal or systemic lipid exposure. We analyzed the data from a population-based case-control study that included 1,163 cases and 1,501 controls to examine the effects of individual fatty acid groups on colorectal cancer risk as well as their interactions with calcium and fiber intake. Odds ratios (OR) and 95% confidence intervals (CI) were estimated by unconditional logistic regression model according to quartile levels of energy-adjusted fatty acid intake. In the bivariable analyses, the risk of colorectal cancer increased with trans fatty acid (TFA) intake (OR for top vs. bottom quartile 51.46, 95% CI 1.17–1.59, pvalue for a trend ¼ 3 times per week for 6 months or longer) non-steroidal anti-inflammatory drug (NSAID) use, body mass index (body weight (kg)/body height (m)2), and physical activity index in their 30s, which was the weighted sum of time the subject spent per 24 h as described previously,21 pack–years of cigarette smoking and postmenopausal hormone replacement therapy (in women). The last two variables were forced to be included in the model given the evidence from the literature.19,20 Vitamin D, dietary heme, alcoholic drinks, race and body height were also assessed and were not included in the final model (p > 0.10). Major dietary sources of fatty acids, such as red meat, were not included in the model simultaneously because their inclusions (i.e., controlling their intake levels) alter the interpretation of regression coefficients for individual fatty acids. After exclusion of subjects with missing covariates, the final analytical samples in this study consisted of 1,163 cases and 1,501

Epidemiology

Material and Methods

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Dietary fat and colorectal cancer

Table 1. Nutritional profile of the study population Overall (N52664)

Cases (N51163)

Controls (N51501)

Nutritional characteristics

Unit

Median

(Quartile range)

Median

(Quartile range)

Median

(Quartile range)

p-values

Total energy

Kcal/day

2040

(1581–2691)

2085

(1606–2801)

2023

(1563–2618)

0.004

Protein energy

%

14.8

(13.0–16.9)

14.6

(12.7–16.7)

15.0

(13.2–17.0)

0.002

Carbohydrate energy

%

47.8

(42.3–53.1)

47.6

(42.4–52.6)

48.0

(42.2–53.4)

0.306

Fat energy

%

37.4

(32.8–42.1)

37.8

(33.2–42.0)

37.1

(32.3–42.4)

0.184

Energy-adjusted intake Total fat

g/day

96.05

(86.21–106.46)

96.54

(86.73–106.11)

95.59

(85.99–106.86)

0.583

Saturated fatty acids

g/day

28.66

(25.18–32.32)

28.75

(25.51–32.36)

28.61

(24.86–32.32)

0.200

cis-MUFA

g/day

36.31

(31.90–40.66)

36.17

(32.00–40.66)

36.33

(31.81–40.67)

0.517

Omega-6 PUFA

g/day

20.21

(16.68–24.42)

19.95

(16.30–24.31)

20.39

(16.91–24.60)

0.019

Omega-3 PUFA

g/day

1.97

(1.66–2.41)

1.96

(1.65–2.40)

1.98

(1.67–2.42)

0.503

Trans fatty acid

g/day

7.71

(6.13–9.24)

7.86

(6.27–9.62)

7.60

(6.04–9.04)

0.004

Calcium

mg/day

899.6

(688.5–1307.7)

858.1

(662.1–1164)

946.0

(711.7–1417)