20 Jun 2018 --- Clinical trials of diets and their health impacts are often plagued by participants’ poor adherence to assigned diets, making it difficult to detect the true effects of those diets. An analysis of small molecules called “metabolites” in a blood sample may be used to determine whether a person is following a prescribed diet, scientists at Johns Hopkins Bloomberg School of Public Health have shown. The new approach, described in a paper in the American Journal of Clinical Nutrition, could provide an objective and relatively easy-to-obtain measure of dietary adherence, potentially greatly reducing the uncertainty of dietary intake estimates.