Design criteria for studies examining individual fatty acid effects on cardiovascular disease risk factors: human and animal studies.

Studies designed to examine individual fatty acid effects in humans and animals are critically dependent on subjects or animal species, experimental diets, and the experimental design used. For both human and animal studies, the numbers of subjects and animals must be adequate for achieving statistical significance and the subjects and animals must be grouped appropriately (eg, age, sex, and cholesterol responsiveness). In animal studies the appropriate species must be selected because some species are unacceptable models. In both human and animal studies, great attention must be paid to the design of the experimental diets. Test diets must be tightly controlled and nutrient specifications must be met and verified by chemical analysis. Ideally, only the fatty acid of interest should vary among the test diets. Two experimental designs are appropriate: crossover and parallel-arm designs. Feeding periods must be of adequate duration for stabilization of endpoints. Attention to these study design issues is imperative for meaningful conclusions to be reached about the effects of individual fatty acids.