It would be very difficult to do a clean study. Whatever numbers the board recommends have tremendous policy implications. These recommendations are used to set targets for food aid programs, to gauge food labeling and health claims, to determine the adequacy of food staples donated worldwide, etc. For example, say we recommend that people have 200 units of vitamin E per day. The RDA also helps us determine which countries need aid, who is deficient, how much food they need to import.
Many countries have their own RDAs.
But obviously, the U.S. RDAs are very influential, thoroughly researched, and based on a lot of data. I see a time when you go to the supermarket with your magnetic card, which has all your family history, risk factors, lifestyle preferences, whatever. You put it in a machine at the entrance, and the grocery list comes out. Some of the food will be fortified to a level where you wouldn't need to take a particular supplement. You'd just need to consume that food.