Dietary patterns and risk of oral and pharyngeal cancer: a case-control study in Rio de Janeiro, Brazil Padrões dietéticos e câncer oral e de faringe: um estudo caso-controle no Rio de Janeiro, Brasil

The study investigated the association between dietary patterns and oral cancer as part of a Latin American multicenter hospital-based casecontrol study, and included 210 incident cases of oral cancer and 251 controls. Dietary data were collected using a Food Frequency Questionnaire (FFQ). Factor analysis was used to define dietary patterns, which were categorized into terciles. Odds ratios (OR) with 95% confidence intervals (95%CI) were calculated using unconditional multiple logistic regression. The patterns “prudent”, characterized mainly by vegetables and fruits, and “traditional”, by rice, and pulses showed an inverse association with oral cancer for the higher tercile, respectively, OR = 0.44; 95%CI: 0.25-0.75, p value for trend (ptend) = 0.03; OR = 0.53; 95%CI: 0.30-0.93, ptend = 0.06. The “snacks pattern” was not associated with oral cancer. Besides the protective effect of a diet rich in vegetables and fruit, our data suggest that the traditional Brazilian diet, consisting mostly of rice and beans, may improve protection against oral cancer. Mouth Neoplasms; Feeding Behavior; Food Consumption Introduction Oral and pharyngeal cancer, grouped together, represent the sixth most common cancer in the world 1. The annual estimated incidence is around 275,000 for oral and 130,300 for pharyngeal cancers excluding nasopharynx, with twothirds of these cases occurring in developing countries 1. There is a wide geographical variation (approximately 20-fold) in the incidence of this cancer, and parts of Latin America and the Caribbean (including Brazil, Uruguay and Puerto Rico) are characterized by high incidence rates for oral cancer (excluding lip) 1. In Brazil, excluding skin cancer, oral and pharynx cancer represent the fifth incidence of cancer in men and the seventh in women. The incidence rates ranged from 2.9/100,000 in Belém, Pará State (1996-1998) to 7.6/100,000 in São Paulo (1997-1998) 2. The most recent Brazilian National Cancer Institute (INCA) estimates for Rio de Janeiro State are 1,510 new cases for men and 520 for women 3. Most are squamous cell carcinomas that develop after exposure to carcinogens such as tobacco and alcohol 4. Oral and pharyngeal cancer involves complex causality, but available evidences suggest that environmental factors are driving the geographic patterns 5. The role of diet in the etiology of oral and pharyngeal cancer remains unresolved. A recent revision concluded that consumption of non-starchy vegetables, fruits, and foods containing caroteARTIGO ARTICLE Toledo ALA et al. 136 Cad. Saúde Pública, Rio de Janeiro, 26(1):135-142, jan, 2010 noids probably protect against these cancers but available evidence is still inconsistent for other dietary components 6. Dietary patterns refer to the concept of “total” diet, thereby transcending the traditional focus on individual foods or nutrients common in nutritional epidemiology and overcoming the limitations associated with this approach. Dietary patterns are measured using two general strategies: (1) empirical methods (a posteriori) use data aggregation and reduction procedures to generate patterns based upon dietary intakes as they are actually consumed; and (2) theoretical methods (a priori) employ extant nutrition knowledge of healthy diets to generate “optimal” diets, usually by creating a composite measure of total dietary quality. The utilization of both methods has gained increasing popularity in the past decade and the literature has burgeoned in recent years 7,8,9. The main technique used in the “a posteriori” approach is the analysis of principal components and subsequent factor analysis 10. In factor analysis, instead of arbitrarily adopting a diet indicator, data objectively point towards how the measurements aggregate 11. The analysis of dietary patterns may help to show the influence of diet on risk of oral cancer. Thus, the present study was aimed at investigating associations between dietary patterns and oral cancer.