NOAEL

The NOAEL (No Observed Adverse Effect Level) is a standard toxicological endpoint used in novel food safety assessment. It represents the highest dose or exposure level tested in a study at which no statistically or biologically significant adverse effects are observed compared to the control group.

In the context of novel food assessment, the NOAEL is typically derived from the 90-day subchronic oral toxicity study in rodents (OECD Test Guideline 408). EFSA uses the NOAEL to calculate a margin of exposure (MOE) or to derive a health-based guidance value by applying appropriate safety factors — typically a factor of 100 (10 for interspecies extrapolation and 10 for intraindividual human variability).

The NOAEL approach has limitations: it depends on the dose levels selected in the study design, it does not use all available dose-response data, and it can be insensitive to the shape of the dose-response curve. For these reasons, EFSA increasingly accepts or recommends the benchmark dose approach as an alternative.

When reporting a NOAEL, the study must clearly state the dose, the species and strain tested, the duration of exposure, and the critical effect (the adverse effect observed at the next higher dose level, known as the LOAEL).