In clinical nutrition we are used to dealing with the clinical managem
ent of patients, but of equal or greater importance is the study of ho
w nutrition affects the development of diseases or modifies its manifi
estations. This field is complex and links physiological studies of nu
trition to the epidemiological analyses which form the basis of thinki
ng in public health in Mexico today. Thus a number of studies have inv
estigated the nutritional risk factors leading to the development of d
iseases such as heart disease and cancer (1-10). This epidemiological
research requires the difficult task of accurately assessing the food
consumption of individuals: with poor methodologies the chances of err
oneous results are very high. This has implications for both group and
individual comparison. Physiological studies on the effects of highly
controlled changes in food intake on risk factors then allows die epi
demilogy to be interpreted in metabolic terms. In this paper we illust
rate some of the benefits of metabolic studies and some of the require
ments for this succesfull conduct.