The term "Adequate Intake" (AI) refers to a recommended daily nutrient intake level that is assumed to be sufficient to maintain nutritional adequacy in a healthy population when there is not enough scientific evidence to establish a Recommended Dietary Allowance (RDA). The "Tolerable Upper Intake Level" (UL) is defined as the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects for almost all individuals in the general population. It represents the maximum chronic daily intake of a nutrient from all sources that can be tolerated without appreciable risk of harm. The UL is not a recommended intake level but an upper safety limit to avoid toxicity or other adverse effects. In summary:

• Adequate Intake (AI) is a recommended intake used when an RDA cannot be determined, representing a level expected to maintain health.
• Tolerable Upper Intake Level (UL) is the maximum intake unlikely to cause harm in most people.

These definitions are part of the Dietary Reference Intakes used for assessing and planning nutrient intakes in populations.