Interindividual differences were recognised early in nutrition research, and phenotypes were described. With the progress in genetics, biochemical disorders with high nutritional relevance were linked to a genetic origin. Genetic disorders with pathological effects were described, e.g. the few genes with pathological obesity. Other gene polymorphisms were described with consequences for human nutrition. The folate metabolism is a good example, where a common polymorphism exists for the gene that encodes the methylenetetrahydrofolate reductase (MTHFR). It was realised however, that many, possibly thousands of other gene polymorphisms might result in minor deviations in nutritional biochemistry, where only marginal or additive effects would result from these deviations. The tools to study the physiological impact were not available at the time and are only now becoming available.

Nutrigenomics is associated with the issue of personalized nutrition, since claims are being made that differences in genotype should result in differences in the diet and health relationship."

Source: Wikipedia - http://en.wikipedia.org/wiki/Nutrigenomics