Strategies for implementing dietary guidance

It is said that "genetics and nutrition are both on the threshold of their golden epoch" as a result of technological advances such as those in molecular biology. However, medical researchers and other health professionals are focusing on the interaction of genetics and nutrition and, in particular, how nutrients influence gene expression. Knowledge of the interaction of genetics and nutrition may soon reshape health and nutrition recommendations. Genetic factors not only influence growth and development, but also most chronic multifactorial diseases in which nutrition factors play a role. Coronary heart disease, essential hypertension, obesity, diabetes mellitus, cancer, and osteoporosis all are influenced by both genetics and environment (e.g., diet). This Digest reviews new findings regarding the role of genetics in the above nutrition-related diseases and the potential impact of these findings on dietary advice. Individuals differ not only in visible traits such as skin, hair, and eye color, but also in other genetically determined biochemical and immunological characteristics which influence their ability to handle environmental insults (e.g., chemical carcinogens, diets high in saturated fat and cholesterol). Recently, extensive genetic variability has been found to exist at the level of deoxyribonucleic acid (DNA), the vital substance of heredity present in each human gene. Scientists are identifying DNA segments of genes that carry coding for disease. As a result of mapping of the human genome (i.e., the total genetic endowment packaged in the 46 chromosomes), it may be possible to identify genetic patterns that predispose to specific chronic diseases. Genetics and nutrition interact in a number of ways. Genetics affects nutrient absorption, metabolism, and excretion, as well as factors influencing food intake such as taste perception and degree of satiation. Differences in the activity of enzymes can cause variations in nutrient requirements. Not only does genetics influence nutrition, but also nutrition can influence genetics. For example, in the process of human evolution, nutritional factors such as starvation may have selected for genotypes predisposing to obesity, thereby favoring survival. Perhaps the most important and practical aspect of nutrient-gene interactions relates to a new concept of nutrition policy. Currently, dietary guidance issued to the American public to prevent major chronic diseases does not take into consideration genetic differences in individuals' response to diet. Increased understanding of genetics and, in particular, the availability of genetic markers, may allow individualization of diets to lower the risk of specific diseases.