Fried potatoes and human cancer.

Abstract

Pelucchi et al.1 reported in a study including approximately 9,000 cancer cases and 20,000 controls no correlation between fried/baked potato intake and human cancer. Patients and controls were asked for the weekly frequency of consumption of fried/baked potatoes in a food frequency questionnaire. For statistical analysis, successive levels of consumption frequency of 0, 1 and > 1 portion/week were chosen, representing approximate tertiles among controls. None of the computed odds ratios for the highest tertile of intake was significantly different from the null value. This finding is not surprising since there is no evident reason why the consumption of fried potatoes as part of a balanced diet should increase cancer risk. However, we assume that the study of Pelucchi et al.1 was conducted to investigate if the consumption of foods rich in acrylamide may be important in relation to human cancer. Fried/baked potatoes are an important source of acrylamide,2 a substance formed during food processing and preparation of food3, 4 and probably carcinogenic to humans.5 It is therefore of major importance to undertake additional research to understand any potential relation of acrylamide intake via foods and cancer risk. Unfortunately, the study of Pelucchi et al.1 was not designed to answer this important question. In their analysis, the authors did not include some very important variables: intake of other foods important in regard to total daily acrylamide intake, e.g., coffee, biscuits and bread, and browning degree of the potato products. In a recent study (Swiss Federal Office of Public Health assessment of acrylamide intake by duplicate diet study; www.bag.admin.ch), we were able to show that coffee intake may be responsible for up to 36% of the daily acrylamide intake. Therefore, a heavy coffee drinker but restrictive on fried potatoes may have a significantly higher acrylamide intake than a person drinking no coffee but consuming 2 portions of French fries per week. As shown by Noti et al.,2 another important factor not included in the analysis is the degree of browning of the consumed potato products. French fries may have acrylamide concentrations of 20–1,000 μg/kg, depending on starting material (variety and storage) and method of preparation. The concentration of acrylamide strongly correlates with the color of the French fries: the darker the product, the higher its acrylamide content. In regard to daily acrylamide intake and cancer risk, 1 serving of very dark French fries may therefore be much more important than 5 servings of very light French fries. A few months ago, Mucci et al.6 were the first to report an absence of an association of acrylamide intake and cancer. However, the authors put their results into perspective by discussing possible limitations. Mucci et al.6 detected the same possible weaknesses that we criticize in the study by Pelucchi et al.1: lack of inclusion of other foods important in regard to total daily acrylamide intake, and large variation of the acrylamide content of included foods making intake calculations difficult. Both factors may lead to an incorrect estimation of acrylamide intake leading to an underestimation of a true association with cancer risk.6 The formation of acrylamide in foods is a complex issue with many important parameters. Therefore, epidemiologic studies have to be specifically designed taking this complexity into account. Mucci et al.6 proposed validation studies of acrylamide dose using existing food questionnaires leading to more reliable data of actual acrylamide intake. The conclusion of Pelucchi et al.1 that there is no association between an increased consumption of fried/baked potato products and cancer risk may therefore be very misleading—it all depends on the way of preparation of the potato products, on the intake of other foods rich in acrylamide and on the intake of foods carrying protective factors (e.g., vegetables and fruits). Reanalysis of already-assessed data is very tempting but in the case of acrylamide it may not lead to important answers. Acrylamide is a potential carcinogenic agent and it is important that industry, scientists and food authorities undertake joint efforts to reduce its concentration in our diet. However, we are in agreement with the authors that a moderate consumption of fried/baked potatoes may not be the most important risk to human health caused by food intake. Even more so if this moderate intake is on the background of a diet rich in vegetables and fruits. Yours sincerely, Michael U. Beer, Josef Schlatter, Vincent Dudler, Otmar Zoller