The Food and Nutrition Board of the Institute of Medicine establishes safe upper limits for many of the vitamins and minerals so you can avoid any adverse health effects that may result from ingesting high levels of a specific vitamin or mineral. According to the National Academy of Sciences, the tolerable upper intake level for a specific vitamin or mineral is the highest level of daily intake that will not result in adverse health effects for the majority of the population.
B Vitamins
For the majority of the B vitamins, no safe upper limit has been established because no toxic effects have been reported with large doses. These vitamins include biotin, pantothenic acid, riboflavin, thiamine and vitamin B-12. For folic acid, the safe upper limit has been established at 1,000 mcg, which applies to folic acid from supplements and fortified foods only. No adverse effects have been reported from high intakes of folic acid from foods. The safe upper limit for niacin is 35 mg. Vitamin B-6 intake should not exceed 100 mg daily, a level that could not be achieved without supplements, due to concern for possible neurological symptoms at high doses, according to the Linus Pauling Institute.
Fat-soluble Vitamins
The fat-soluble vitamins include vitamins A, D, E and K. The safe upper limit for vitamin A is 3,000 mcg or 10,000 IU of preformed vitamin A. Preformed vitamin A comes from animal sources, including dairy products, butter and eggs, and from fortified foods like breakfast cereals. There is no toxicity associated with carotenoids, which is the form of vitamin A found in plants. The safe upper limit for vitamin D is 4,000 IU, while daily intake of vitamin E should not exceed 1,500 IU, which is equivalent to 1,000 mg. No safe upper limit has been established for vitamin K.
Vitamin C
The tolerable upper intake level for vitamin C for adults is 2,000 mg in order to prevent diarrhea and other gastrointestinal problems that may occur at high doses. According to the Linus Pauling Institute, there is no scientific evidence to support adverse health effects for up to 10,000 mg of vitamin C daily.
Minerals
Most of the minerals have an established safe upper limit with the exception of chromium and potassium, for which no upper limit has been established. The upper limit for calcium is 2,500 mg, while the upper limit for copper and fluoride is 10,000 mcg and 10 mg, respectively. To avoid toxicity, you shouldn't ingest more than 1.1 mg of iodine daily or more than 45 mg of iron. The upper limit for magnesium of 350 mg applies to supplemental magnesium only, not to the magnesium found in foods. Molybdenum intake should not exceed 2,000 mcg daily, while phosphorus should be kept under 4,000 mg. The safe upper limit for selenium is 400 mcg and for zinc is 40 mg. Sodium intake should not exceed 2,300 mg daily, which translates to 5,800 mg of sodium chloride, or table salt.
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