Colorectal Cancer and Nonfermented Milk, Solid Cheese, and Fermented Milk Consumption: A Systematic Review and Meta-Analysis of Prospective Studies

Abstract

Colorectal cancer is the second most prevalent cancer worldwide. A systematic review and meta-analysis of prospective studies was conducted to examine the association between intake of different types of dairy foods during adulthood and the development of colorectal cancer, specifically comparing nonfermented milk, solid cheese, and fermented milk. Seven databases were systematically searched and 15 cohort studies selected for inclusion, involving over 900,000 subjects and over 5200 colorectal cancer cases. Meta-analysis resulted in an overall relative risk of colon cancer of 0.74 (95% confidence interval 0.60–0.91) in men consuming nonfermented milk (highest intake category averaging 525 g/day). No association was found between consumption of nonfermented milk and rectal cancer in men or nonfermented milk and colon or rectal cancer in women. No protective association was found between consumption of solid cheese or fermented milk and colorectal cancer. Reasons for the differences in the impact of nonfermented milk, solid cheese, and fermented milk in the colon are discussed. This meta-analysis supports the inverse association between nonfermented milk consumption and risk of colon cancer in men, and provides an evidence base to assist in the formulation of dietary guidelines involving dairy foods.

Keywords:

• Cheese
• colorectal neoplasms
• dairy products
• meta-analysis
• milk
• yogurt

ACKNOWLEDGMENT

The authors thank Jia Hwa Lee for her help with publication recovery and coding of studies. R.A. Ralston conducted the November 2010 search, determined studies for exclusion and inclusion, extracted data from retrieved studies, conducted the meta-analysis, and drafted the paper. H. Truby oversaw and advised the entire study, contributed ideas throughout the review, and helped with paper revision. C.E. Palermo determined studies for exclusion and inclusion, extracted data from included studies, and contributed to paper revision. K.Z. Walker oversaw and advised the entire study, designed the review process, chose studies to be retrieved, and contributed to paper preparation and revision. All authors approved the final manuscript. None of the authors have a conflict of interest to disclose. This work was undertaken as part of a systematic literature review to update the Dietary Guidelines for Australians by the Dietitians Association of Australia under contract to the National Health and Medical Research Council, Australia.

Notes

^aAdjusted for age;

^bAdjusted for age, gender, occupation, smoking, geographic area, BMI, and total energy intake;

^cAdjusted for age, family history of colon cancer, previous intestinal polyp, screening, smoking, aspirin use, physical activity, BMI, total energy, saturated fat, and dietary fiber intakes, and alcohol and red meat consumption;

^dAdjusted for education, family history of colon cancer, smoking, physical activity, BMI, total energy intake, and alcohol consumption;

^eAdjusted for age, education, family history of CRC, history of diabetes, smoking, aspirin use, physical activity, BMI, total energy, saturated fat, and vitamin D intakes, alcohol, fruit, vegetable, and red meat consumption, and multivitamin use;

^fAdjusted for age, education, income, survey season, nonsteroidal anti-inflammatory drug use, total energy and dietary fiber intakes, and tea consumption;

^gAdjusted for age, randomized treatment assignment, family history of CRC, history of colon polyps, smoking, menopausal status, baseline postmenopausal hormone therapy use, physical activity, BMI, total energy and saturated fat intakes, red meat and alcohol consumption, and multivitamin use;

^hAdjusted for age, family history of CRC, smoking, aspirin use, physical activity, BMI, and alcohol and red meat consumption;

ⁱAdjusted for age, education, family history of CRC, smoking, hormone replacement therapy use, physical activity, BMI, total energy and saturated fat intakes, fruit and vegetable consumption, and long-term multivitamin use;

^jAdjusted for age, ethnicity, time since cohort entry, family history of CRC, previous intestinal polyp, smoking, hormone replacement therapy use (women), nonsteroidal anti-inflammatory drug use, physical activity, BMI, total energy and dietary fiber intakes, and regular multivitamin use;

^kAdjusted for age, gender, smoking, and alcohol intake;

^lAdjusted for age, gender, family history of colon cancer, smoking, aspirin use, physical activity, BMI, and alcohol use;

^mAdjusted for age, education, BMI, total energy, folic acid, and vitamin C intakes, and alcohol and red meat consumption;

ⁿAdjusted for age, gender, and region of residence;

^oAdjusted for age, education, supplement group, smoking, physical activity at work, BMI, and alcohol consumption.

^aBased on a typical adult consuming 1600+ kcal/day (US) or age 19–50 years (Canada, Australia, United Kingdom);

^bRecommended serving sizes for the United States, Canada, Australia, and the United Kingdom are based on the Dietary Guidelines for Americans (U.S. Department of Health and Human Services and US Department of Agriculture, 2010), Eating Well with Canada's Food Guide (Health Canada, 2007), The Australian Guide to Healthy Eating (Kellett et al., 1998), and the UK Dairy Council (The Dairy Council, 2007), respectively;

^cCalculated using the NUTTAB 2006 online version (Food Standards Australia New Zealand, 2006).