Precision medicine refers to treatment or prevention strategies in a group of individuals identified by their phenotype or genotype. Dietary components or patterns may play an important role in precision medicine. There is emerging evidence to support a role for n-3 (ω-3) fatty acids in lowering blood pressure and reducing the extent of subclinical atherosclerosis in people born with impaired fetal growth, a group at increased risk of coronary artery disease partly due to an increased risk of hypertensive disorders. The evidence linking n-3 fatty acid intake with less atherosclerosis and lower blood pressure in people with impaired fetal growth has been derived from studies in young children, adolescents, and adults and has included dietary assessments by questionnaires and circulating biomarkers. Furthermore, results appear to be similar for shorter chain n-3 fatty acids from plant sources and long-chain n-3 fatty acids from marine sources. The general framework used to develop this evidence, consisting of hypothesis-driven analyses from observational studies and post hoc analyses of a randomized clinical trial, before a priori testing as a primary outcome in randomized trials, is presented and proposed as a potential model for the identification and development of dietary precision medicine strategies.