Background on ADI (taken from The Clinical Evaluation of a Food Additive; Assessment of Aspartame)*
Before a food additive is approved, regulatory agencies require specific scientific evidence that is safe for its intended uses and that its projected level of intake (estimated daily intake) is less than the ADI. If such projections exceed the ADI, regulatory agencies may impose restrictions on approvals for certain uses or restrict future approvals for new categories of use.
The concept of an ADI was introduced in 1961 by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Expressed in milligrams of additive per kilogram body weight, it is the dose, if consumed on a daily basis over a lifetime, that would cause no adverse effects. The ADI for an additive is not intended to define the maximum dose that would be safe to consume on any given day. It is implicit that a person may occasionally consume an additive in quantities in excess of the ADI without untoward effects.
The ADI is generally based on the results from animal toxicology studies. These studies are used to determine the no-observed-effect level (NOEL) for the additive. The NOEL is usually divided by 100 to determine the ADI for a food additive, thus, providing a 100-fold safety factor to account for species differences and inter-individual variation among humans.