III. Ways of quantitating nutrient requirements
- Requirements for different nutrients are (and sometimes have to be) measured according to different criteria.
- The total amount of information and/or number of subjects in studies is often not great enough to assure total reliability. The experimental subjects are people, and people (even prisoners) have rights. With some nutrients more is known about animal nutrition than about human. One can do the experiments on animals, and there may be bigger direct payback than there would be for the more difficult task of studying the corresponding human nutrition issue.
- There can be political aspects. Sometimes groups that don't want to look bad because their population is largely below some proposed criterion value will lobby to have the official value lowered.
- In spite of their weaknesses, the values established by scientific process are the best we have, and are far better than any alternative that comes to mind.