The Cochrane Collaboration is an international, not-for-profit organisation that aims to help people make well-informed decisions about health care by preparing, maintaining and promoting the accessibility of systematic reviews of the effects of health-care interventions. Cochrane systematic reviews are prepared according to predefined, explicit methodology, and published in The Cochrane Library. The abstracts and plain English summaries of the reviews are freely available on the Internet. All reviews are prepared and maintained under the editorial control of 50 Cochrane Collaborative Review Groups that focus on (groups of) health problems. The work of Collaborative Review Groups is supported, among others, by people working in Cochrane Fields. Cochrane Fields focus on dimensions of health care other than health problems. To date, the issue of nutrition has not been addressed sufficiently in The Cochrane Collaboration. Nutrition issues are very important for day-to-day health care and the initiatives to establish a new Cochrane Diet and Nutrition (Sub)Field will help to promote the preparation of systematic reviews of nutritional interventions by the variety of Collaborative Review Groups to whom such interventions are relevant. Many issues regarding nutritional interventions, however, are complex, and methodological challenges will have to be overcome. A Cochrane Diet and Nutrition (Sub)Field with experts on nutritional research can help fill this gap and make those reviews more possible.