The occurrence of adverse health effects from ingestion of any substance depends on its inherent toxic potential, the amount of intake, and the biological characteristics of the exposed individual.

A safe intake is one that provides an acceptable margin of safety below the intake that carries risk of adverse effects.

If appropriate data are available, applying fixed safety factors, systematically varying safety factors or using other methods to identify reasonable limits for safe intakes.

A crucial factor in understanding the margin of safety that a particular intake is likely to provide is the adequacy of the data to estimate the likely frequency of the adverse response among persons with that intake.

For a few nutrients there are sufficient numbers of reports of adverse effects over a sufficiently wide range of exposures to allow estimation of lowest adverse effect levels ; for other nutrients the reports of adverse effects are too infrequent or inconsistent to support estimations that are meaningful.