below the UL, there is good assurance that the intake will not cause adverse effects, given current knowledge. At intakes above the UL, the risk of adverse effects increases. Although there is no established benefit for healthy individuals associated with consumption of nutrients or food components above the RDA or AI, there is little concern of an increased risk of harmful effects of consumption up to the UL.
Ordinarily, the UL refers to intake from food, fortified food, water, and supplements. Nutrients are often available from a variety of food and nonfood sources. For fluoride, for example, intake from all sources must be considered, including water and dental products. Combined with other sources of fluoride, the over-use of fluoride-containing dental products may place many young children at risk of dental fluorosis.
To avoid exceeding the adult UL for calcium of 2.5 g (62.5 mmol)/day, intake from food, fortified food, and supplements must all be considered. The UL for calcium was determined based in part on studies in which hypercalciuria was related to both dietary and supplemental intakes of calcium. For phosphorus, intakes from both food and supplements are to be considered when comparing intakes with the UL of ~4.0 g (130 mmol)/day for adults. However, for individuals requiring very high energy intakes, phosphorus intake from diet alone may exceed the UL without adverse effects.
To avoid exceeding the UL for vitamin D of 50 µg (2,000 IU)/day, considering intake from all sources is important, but ordinarily only intake from food, fortified food, and nutrient supplements provides notable amounts. (Apart from fatty fish and liver, high concentrations of vitamin D do not occur naturally in commonly eaten foods in the United States and Canada.) Individuals who have high intakes of vitamin D-fortified foods (such as milk and margarine) and of vitamin D supplements (in multivitamin preparations, alone, or in fish oil) should keep the combined average daily intake below the UL of 50 µg (2,000 IU)/day to minimize the risk of developing hypercalcemia.
For many nutrients, such as magnesium, adverse effects associated with high levels of intake from food sources have not been reported. The UL of 350 mg (14.6 mmol)/day was set for magnesium from nonfood, over-the-counter pharmacologic products. This is the intake at which an individual might first experience an adverse effect (diarrhea) from ingestion of a nonfood source of magnesium for at least 1 week. Since the UL for magnesium applies only to nonfood sources, individuals should not be concerned with trying