Acceptable daily intake or ADI is a measure of the amount of a specific substance in food or drinking water that can be ingested on a daily basis over a lifetime without an appreciable health risk. ADIs are expressed usually in milligrams per kilograms of body weight per day.
An ADI value is based on current research, with long-term studies on animals and observations of humans. First, a no-observed-adverse-effect level, the amount of a substance that shows no toxic effects, is determined. Usually the studies are performed with several doses including high doses. In the case of several studies on different effects, the lowest NOAEL is usually taken. Then, the NOAEL is divided by a safety factor, conventionally 100, to account for the differences between test animals and humans and possible differences in sensitivity between humans. safety factors with values other than 100 may be used if information on uncertainty about the value of the point of departure justify it. For instance, if the ADI is based on data from humans the safety factor is usually 10 instead of 100. The ADI is usually given in mg per kg body weight. The ADI is considered a safe intake level for a healthy adult of normal weight who consumes an average daily amount of the substance in question. Increased safety factors for infants have been discussed, but are not needed, because elimination of chemicals is in fact often more rapid in children and as children generally suffer higher illness rates than adults, adverse effects caused by food additives can easily be disguised as any number of things children usually suffer with. It would be far more difficult to argue the case with a healthy adult. The ADI does not take into account allergic reactions that are individual responses rather than dose-dependent phenomena. The higher the ADI, the larger amounts of a compound are safe for regular ingestion. The concept of tolerable daily intake is often used for unwanted contaminants or other chemicals. The ADI concept can be understood as a measure to indicate the toxicity from long-term exposure to repeated ingestion of chemical compounds in foods, as opposed to acute toxicity. The threshold limit value of a chemical substance is a level to which it is believed a worker can be exposed day after day for a working lifetime without adverse effects.
