Experience indicates that individuals not developing symptoms in the first 20 days are not likely to do so thereafter. Any method of oral administration that facilitates a double-blind trial is acceptable. For example, the material can be incorporated into cookies, cakes, pudding, or other acceptable supplements to a usual diet if it can be introduced so that its presence cannot be specifically identified. Novel foods in powder form can often be tested by allowing the subjects to mix them into bouillon or any of a variety of fruit juices according to individual preference, and they can vary their choice from day to day. In this case, however, there must be available a similar control material for which tolerance is already well established.
Experienced nutritionists can usually find an acceptable method of administration.
All subjects recruited should have the opportunity to taste the materials to be consumed before making a commitment to the trial. If this is not done, a number of subjects are likely to confound the trial by dropping out in the first few days because they do not like the taste, texture, smell, or some other aspect of the substances offered. For example, yeast as a vitamin supplement may be consumed at less than 5 grams daily, as a functional food additive rarely more than 10 grams, but as a significant protein supplement, the amount might be 30 grams or more, providing it does not supply more than 2 grams of nucleic acid. If the amount intended for testing is more than 15 to 20 grams per day, it should be divided into two or more feedings per day. If a supplement is intended to be added to a traditional staple like bread or a rice dish, then it should be given daily or even more frequently, in relatively large amounts, following normal dietary practice so that the experimental material is fed at the upper intended limit of use, which may involve daily administration of 30 grams or higher.