Current approaches for policy analysis and development rely upon a narrow and/or limited range of perspectives for framing and analyzing policy problems and potential measures to address them. The purpose of this project is to develop improved approaches for policy analysis and development related to gene-nutrient interactions that are more integrative in terms of the disciplinary perspectives and the parties involved in framing the problem and potential solutions.

In the coming years, nutritional genomics will reveal many examples of gene-nutrient interactions, some of which have high prevalence and important consequences for public health. Finding effective and appropriate measures to address these interactions will require improved methods for evaluating policy options. This project contributes to that goal by developing a microsimulation model related to iron overload, a condition for which about one million Americans are at risk. The current policy is therapeutic phlebotomy at mid-life (taking units of blood weekly for several years). The model we developed compared that to de-fortification, genetic screening, and inidividual dietary modification.

The purpose of this research is to quantify the role of dietary iron in total body iron (TBI) accumulation among homozygotes for the HFE gene associated with hemochromatosis. A Monte Carlo model was built to simulate iron accumulation based on findings from human feeding experiments and national dietary surveys. A hypothetical cohort of 1,000 homozygotes starting at 25 years-of-age is used in 39-year simulations. Iron accumulation is compared under three scenarios. At baseline, there is no dietary modification. Under the second scenario, allowable food iron intake is capped at 200 percent RDA. Under the third scenario, allowable food iron intake is capped at 100 percent RDA. At baseline, by age 64, the percentages of males with TBI greater than 10g, 15g and 20g are 93.2 percent, 49.6 percent and 14.7 percent, respectively. Under the second scenario in which 55 percent of men originally had iron intakes above 200 percent RDA, the corresponding percentages are 92.0 percent, 40.5 percent and 10.2 percent respectively. Under the third scenario, in which 100 percent of men originally had iron intakes above 100 percent RDA, the corresponding percentages are 70.3 percent, 21.3 percent and 4.1 percent, respectively. The percentage of females with increased TBI is lower than males and the effect of dietary modification on iron accumulation is more modest. In conclusion, high iron intake increases the TBI accumulation among HFE homozygotes and variation in iron intake accounts for some of the incomplete penetrance in this condition.

This research demonstrates the need for researchers and policy analysts to use innovative methods to integrate diverse sources of information (e.g. molecular biology, human feeding trials, national dietary surveys) to evaluate policy options related to gene-nutrient interactions. Microsimulation is one such method but it is underutilized at present in nutrition.

Gene-nutrient interactions

This research used graduate student support from the department and faculty time. No external funding.

Min Tao