Despite being phenotypically quite diverse, humans are genetically mostly the same, with two individuals differing by <1% in their genomes on average. Precision nutrition, sometimes called personalized nutrition, or nutrigenetics, is when individuals receive diets tailored to their personal genetic make-up. The most widespread, inexpensive form of genetic testing is the DNA microarray (Genome-wide association studies: GWAs) containing probes that can quickly detect genotypes at hundreds of thousands of SNPs across the genome. GWAs have discovered many genetic variants associated with specific nutrition-related traits, that in turn can result in gene–diet interactions and human diseases. Together, these findings raise the critical question of whether dietary recommendations could be tailored to individuals based on genetic variation and how significant the impact of precision nutrition could be in contrast to conventional recommendations. A growing number of companies now offer direct-to-consumer, genetically-based nutritional testing (DTC-GT) and advice. However, precision nutrition is at a very early stage, especially given the low prediction of variation and the complexity of genetic alterations. The recent development of polygenic risk scores in combination with lifestyle scores improved our tools to assess in a holistic way personalized nutritional recommendation based on the DNA variation.