Tolerable Upper Intake Level (UL)
The highest average daily intake of a nutrient likely to pose no risk of adverse health effects in almost all individuals in a specified life-stage group.
Also: UL
As intake exceeds the UL, the risk of adverse effects rises. The UL is set using a no-observed-adverse-effect level (NOAEL) or lowest-observed-adverse-effect level (LOAEL) divided by an uncertainty factor. For nutrients without sufficient toxicity data no UL is set, which is not the same as confirming safety at high intakes.
How each textbook covers it
Advanced Nutrition and Human Metabolism, 8th ed. (Gropper) — Glossary
DRI value above which the risk of adverse effects begins to rise. Used to assess the safety of high nutrient intakes from food, water, and supplements combined.
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Krause and Mahan's Food and the Nutrition Care Process, 16th ed. — Chapter 10
The UL is a safety ceiling, not a target. Intakes above the UL increase risk of toxicity. ULs are especially important for fat-soluble vitamins (A, D, E), iron, and supplemental forms of folic acid, magnesium, and niacin where adverse effects are documented.
Modern Nutrition in Health and Disease, 12th ed. — Ch 109: Dietary Reference Intakes
As intake exceeds the UL, the risk of adverse effects rises. The UL is set using a no-observed-adverse-effect level (NOAEL) or lowest-observed-adverse-effect level (LOAEL) divided by an uncertainty factor. For nutrients without sufficient toxicity data no UL is set, which is not the same as confirming safety at high intakes.
Related terms
AI, Adequate Intake, DRI, Dietary Reference Intakes, EAR, Estimated Average Requirement, Hypervitaminosis, RDA, Recommended Dietary Allowance