ISSUES IN THE DESIGN AND INTERPRETATION OF STUDIES OF FATTY-ACIDS ANDCANCER IN HUMANS

The methods used in nutritional epidemiology to study the relations be tween fatty acids and cancer risk include ecologic studies, case-contr ol studies, cohort studies, and intervention trials examining either i ntermediate markers of cancer risk or cancer incidence. Each type of s tudy design has its particular strengths and weaknesses. The inaccurac y of estimates of fatty acid intake from the use of dietary questionna ires linked to nutrient databases is a major limitation in nutritional epidemiology. Information on the concentrations of fatty acids in the circulation or in adipose tissue can complement estimations of dietar y intake. Cancer prevention studies now underway are designed to rest whole-diet effects on neoplasia and will not be able to separate the e ffects of specific fatty acids from those of other nutrients in the di et. The development of better intermediate markers of cancer risk coul d enable the use of experimental methods to assess the relation betwee n specific fatty acids and cancer. Research findings as described in t he literature are complicated both by the multiple hypotheses that can be tested when assessing fatty acid effects and by the uncertainties of multivariate adjustment. Although there are substantial obstacles t o understanding the relations between fatty acid intakes and cancer ri sk, there is no better species than humans for inference about diet an d cancer risk in people.