Behind the scenes of doctors' nutritional advice: the infrastructure of nutrition information that is used in practice.

Though this sixth Heelsum meeting has concentrated on over- and under-nutrition, GPs in their work look after patients with a wide range of diseases that may be helped by different dietary managements (van Weel C. Morbidity in family medicine: the potential for individual nutritional counselling, an analysis from the Nijmegen Continuous Morbidity Registration. Am J Clin Nutr 1997; 65 (suppl 6): 1928s-32s). Much attention is paid to evidence from randomized controlled trials (RCTs). However, most of the nutrition advice by physicians has to be based on accumulated evidence from different sources other than Cochrane reviews and RCTs (Truswell AS. Levels and kinds of evidence for public-health nutrition. Lancet 2001; 357: 1061-2; Truswell AS. Some problems with Cochrane reviews of diet and chronic disease. Eur J Clin Nutr 2005; 59 (suppl 1): s150-4). This paper will briefly review the informational infrastructure of human nutrition, being regularly updated, that is in the background of doctors' advice on diets to their patients. The main parts of this nutrition information include: (i) recommended nutrient intakes/dietary reference intakes, (ii) dietary goals and guidelines, (iii) textbooks of human nutrition, (iv) chapters on nutrition in medical textbooks, (v) ABC of Nutrition, written for GPs and (vi) lastly, a new book about the research on diet and coronary heart disease (CHD) in the 20th century contains the main pieces of evidence that underlie today's nutrition guidance both to people at risk of CHD and for the general community.