Genetic variation in nutritional requirements and susceptibility to disease: policy implications

I have considered several questions that should be answered in order to develop rational public policy for preventing disability and premature death for common disorders for which genes play a role and for which nutritional modification within the normal range can be effective. The sensitivity and predictive value of screening tests, the increment in improved outcomes from screening compared with population-wide changes in diet; the benefit, if any, to be derived from diet modification for those not identified by screening; and the reliability of the laboratories performing the test are some of the factors to be considered. We must bear in mind that many of the common disorders for which we will soon have tests at the gene or gene-product level result from the interaction of multiple factors, both environmental and genetic. Genetic screening will detect only a small proportion of all those destined to manifest a specific disorder, such as coronary artery disease or colon cancer. Dietary modification will also be only one of several interventions that will be efficacious for certain disorders. In some of these cases, genetic screening will prove to be an effective adjunct to general nutritional changes whereas in others it will have little utility and in still others it could play the predominant role in preventing or reducing the severity of the disorder. If we are to reduce the burden of disease most effectively, we cannot ignore factors in our environment and social structure that limit people's ability to control their own health.