An important pitfall of nutritional guidance in medical practice is how to deal with the prevention paradox: a nutritional advice that is good for the population as a whole is not necessarily proven effective for the individual patient. Evidence-based guidelines are needed to support GPs to translate these advices to the individual patient. We illustrate this with two examples: obesity and undernutrition. The Dutch Ministry of Health started a national partnership on overweight. The role of the Dutch College of GPs (NHG) in this process is to insert the GP's perspective and to 'translate' the multidisciplinary guideline into a practice guideline for GPs. A systematic review on nutritional deficiency in general practice in The Netherlands showed a prevalence ranging from 0% to 13%. The 'National Steering Committee Undernutrition' stimulates GPs to pay more attention to undernutrition, in collaboration with the Dutch College of GPs. The Cochrane Primary Health Care Field (Nijmegen) accommodates the Cochrane Diet and Nutrition Sub Field involving the inclusion of evidence from non-randomized studies, which are generally not included in Cochrane Reviews, but which form an important part of the evidence for the role of nutrition. From this international initiative, a national collaboration in The Netherlands between universities, researchers and the Dutch College was founded, which aims to support the foundation of practice-based nutrition counselling in the consulting room.