The European Society of Medical Oncology Symposium (ESMO) on Cancer and Nutrition convened on March 20– 21, 2009, in Zurich, Switzerland. Welcoming 172 participants from 32 countries and from 4 different continents, this symposium was designed to address issues directly relevant to the interface between clinical nutrition and cancer. Was there truly a need for such a conference? The organizers of this meeting contend that the answer is “yes” and cite the following salient examples to show that nutrition really does impact cancer and cancer patients and that focusing a symposium on the interface between nutrition and cancer holds merit. Firstly, it behooves us to always test assumptions of efficacy and safety, particularly with nutritional interventions which are often assumed to be safe. Rates of vitamin/ nutritional supplementation vary dramatically throughout the world, but, in some populations, as many as 80% of individuals are taking them [15, 27]. Despite this high prevalence, only a few studies have demonstrated that supplements prevent cancer, and such studies suggest benefits are confined to nutrient-depleted populations [17]. For example, when one considers the plethora of epidemiologic data that points to an association between beta carotene-rich fruits and vegetables and a diminished risk of lung cancer, it is tempting to conclude—albeit prematurely and unwisely—that beta carotene supplementation is safe and even beneficial. Subsequent studies have nullified this conclusion. In the recent VITAL study that included 77,126 individuals, Satia and others reported that long-term use of patient-reported beta carotene (<10 years) was associated with a greater risk of lung cancer [21]. More importantly, two placebo-controlled, double-blinded randomized clinical trials tested β-carotene at doses of 30 mg in 18,314 individuals and 20 mg in 29,133 individuals all of whom were at high risk for lung cancer. Unexpectedly, both these trials demonstrated that the incidence of lung cancer increased by 28% or more and that, as a result, mortality was worse as a result of beta carotene supplementation. Yes, the unthinkable can happen, and therefore, rigorous testing with proof of safety and efficacy must be established prior to recommending any nutritional supplements, particularly those prescribed at “high” doses. Secondly, one might question whether diet itself has any favorable effect on cancer or cancer recurrence. The Women's Intervention Nutrition Study suggests that it does. A total of 2,437 early-stage breast cancer patients were F. Strasser (*) Oncological Palliative Medicine, Division of Oncology/Haematology, Department of Internal Medicine and Palliative Care Center, Cantonal Hospital, Rorschacherstrasse 95, CH-9007 St. Gallen, Switzerland e-mail: florian.strasser@kssg.ch