Investigators are recommending that black women follow a “prudent dietary pattern” in lieu of a more Western-style diet to prevent the development of colorectal adenomas and, ultimately, colorectal cancer.
Kepher H. Makambi, PhD, with Georgetown University Medical Center in Washington, DC, and colleagues prospectively examined the dietary patterns and risk of colorectal adenomas in 59,000 black women over a 10-year period. All of the women had undergone at least 1 screening colonoscopy involving either sigmoidoscopy or colonoscopy during the follow-up period.
The analysis showed a strong inverse association between prudent dietary patterns and the risk of colorectal adenoma, which may be a precursor to colorectal cancer. A “prudent dietary pattern” referred to a diet that is characterized by a high intake of vegetables, fruits, whole grains, fish, and poultry.
On the other hand, a Western dietary pattern— involving high loading on refined grains, high-fat dairy, processed or nonprocessed meat, sweets, sodas, and snacks—was positively associated with a risk of colorectal adenomas.
“Our results suggest that a prudent dietary pattern may reduce the incidence of colorectal adenomas and that a Western pattern may increase the incidence,” wrote Makambi and associates.
Approximately 16,520 new cases of colorectal cancer were predicted for black women in 2009, and the researchers noted that colorectal cancer is the third most common cancer in black women after lung and breast cancer. Blacks are nearly 30% more likely to die of the disease than whites.
While it has not yet been determined why blacks have higher incidence rates of colorectal cancer, it has been suggested that dietary factors may be a contributor. Research has also shown that blacks are less likely to adhere to a so-called prudent dietary pattern than whites. No prior studies in black women have explored a link between dietary factors and the risk of colorectal adenomas.
The study population included 59,000 women aged 21 to 69 years when they enrolled in the Black Women’s Health Study (BWHS) in 1995. The BWHS is a prospective cohort study of black women from across the United States.
All women completed questionnaires focusing on their food intake at the time of enrollment, and again 6 years later.
During 155,414 person-years of follow-up from 1997 to 2007, a total of 620 incident colorectal adenomas were identified.
The highest quintile of prudent diet, relative to the lowest quintile, was significantly associated with a 34% lower colorectal adenoma risk overall (incidence rate ratio [IRR] = 0.66; 95% confidence interval [CI], 0.50-0.88; P trend <.01). Higher scores on the Western pattern were associated with a higher risk of developing colorectal adenoma (IRR = 1.42; 95% CI, 1.09-1.85 for the highest quintile relative to the lowest; P trend = .01).
Makambi and colleagues said that the Western dietary pattern, particularly red meat, may boost the risk of colorectal adenomas through its effect on colorectal carcinogenesis.
The authors emphasized that their use of a “dietary pattern approach” in their study allowed them to better identify nutrient interactions and a variation in nutrient components than would have been possible had they analyzed the nutrient component of single foods.
Makambi KH, Agurs-Collins T, Bright-Gbebry M, Rosenberg L, Palmer JR, Adams-Campbell LL. Dietary patterns and the risk of colorectal adenomas: the Black Women’s Health Study. Cancer Epidemiol Biomarkers Prev. 2011;20(5):818-825.