Our bodies need vitamins and essential minerals. And, like other things, if taken in large amounts, vitamins and minerals can adversely affect health. Large amounts of anything can be toxic.
Much of the data on adverse health effects from taking large amounts of a vitamin or mineral pertain to acute rather than chronic use. Because nutrients work together, consuming excessive amounts of one nutrient can cause a deficiency of another.
There is no evidence that low levels of vitamin-mineral supplements adversely affect health. This topic is discussed in a recent NebFact, "Vitamin-Mineral Supplements and Their Usage by Adults."
Table 1. Vitamin and Mineral Toxicities in Adults
| Nutrient | 1989 RDAa Men/Women | U.S. RDAb | Lowest Reported Toxic Dose (adults)c |
Symptoms of Toxicity (mild and severe) |
| Vitamin A (preformed) |
1000/800 mcg RE | 5000 IU or 1000 mcg RE | 6000 RE | Headache, vomiting, diplopia, alopecia, dryness of mucous membranes, dermatitis, anemia, insomnia, bone abnormalities, bone and joint pain, hepatomegaly, liver damage, hypercalcemia, hyperlipemia, menstrual irregularities, spontaneous abortions, and birth defects. |
| Vitamin D | 5/5 mcg | 400 IU or 10 mcg | 45 mcg | Nausea, vomiting, excessive thirst and urination, muscular weakness, joint pain, hypercalcemia, disorientation, and irreversible calcification of heart, lungs, kidneys, and other soft tissues. |
| Vitamin E | 10/8 mg -TE | 30 IU or 20 mg -TE | Unknown | Exacerbation of the coagulation defect produced by vitamin K deficiency caused by either malabsorption or anticoagulant therapy. |
| Vitamin K | 80/65 mcg | None | Unknown | Menadione (vitamin K3) but not phylloquinone (vitamin K1) causes hemolytic anemia, liver damage, and, in newborns, kernicterus. |
| Vitamin C (ascorbic acid) | 60/60 mg | 60 mg | 4 g | Nausea, diarrhea, kidney stones, mobilization of bone minerals, systematic conditioning to high intakes, and abortion. |
| Vitamin B1 (thiamine) |
1.5/1.1 mg | 1.5 mg | 300 mg | Gastric upset and prolonged large parenteral injections can lead to sensitized anaphylactoid reactions. |
| Vitamin B2 (riboflavin) |
1.7/1.3 mg | 1.7 mg | 1000 mg | None reported in humans; precipitates in kidneys and hearts of laboratory rats. |
| Niacin (nicotinic acid and nicotinamide) |
19/15 mg NE | 20 mg or 20 mg NE | 1 g | Nicotinic acid - vascular dilation, gastrointestinal
irritation, increased muscle glycogen utilization, decreased serum
lipids, decreased mobilization of fatty acids from adipose tissues, and
hepatomegaly. Nicotinamide - nausea, heartburn, fatigue, dry hair, sore throat, and inability to focus eyes. |
| Vitamin B6 | 2.0/1.6 mg | 2.0 mg | 200 mg | Dizziness, nausea, ataxia, perpheral neuropathy, and systemic conditioning to high intakes. |
| Folic Acid (folate and folacin) |
200/180 mcg | 400 mcg | 5 mg | Can obscure the diagnosis of pernicious anemia by preventing anemia and permitting nerve damage and may reduce zinc absorption; precipitates in kidneys of laboratory rats. |
| Vitamin B12 | 2.0/2.0 mcg | 6.0 mcg | Unknown | None reported; rat studies indicate that folate metabolism may be affected. |
| Biotin | 30-100 mcgd | 0.3 mcg | Unknown | None reported; controversial as to whether reproductive performance of female rats is affected. |
| Pantothenic Acid | 4-7 mgd | 10 mg | 10 g | Occasional diarrhea and edema. |
| Choline | Vitamin-Like Substancee | — | 20 g | Nausea, dizziness, diarrhea, depression, excessive cholinergic stimulation, and EKG abnormalities; salivating, trembling, cyanosis, convulsions, and respiratory paralysis reported in laboratory rats. |
| Carnitine | Vitamin-Like Substancee | — | Unknown | Occasional diarrhea. |
| Inositol (myo-inositol) |
Vitamin-Like Substancee | — | Unknown | None reported except problems may arise when inositol breakdown is impaired (diabetes mellitus, chronic renal failure, galactosemia, and multiple sclerosis). |
| Taurine | Vitamin-Like Substancee | — | Unknown | None reported. |
| Bioflavonoids | Vitamin-Like Substancee | — | Unknown | Some bioflavonoids have been associated with increased occurrence of several cancers. |
| Calcium | 800/800 mg | 1 g | Over 2.5 g | Nausea, constipation, hypertension, hypercalcemia, kidney stones, myopathy, and may inhibit absorption of iron and zinc; individuals with conditions that cause hypercalcemia or nephrolithiasis should not take calcium supplements. |
| Phosphorus | 800/800 mg | 1 g | Over 2.5 g | Calcium antagonism which can result in tetany and convulsions. |
| Magnesium | 350/280 mg | 400 mg | 6 g | Nausea, diarrhea, hypotension, bradycardia, vasodilation, EKG changes, coma, and cardiac arrest. |
| Iron | 10/15 mg | 18 mg | 100 mg | Bloody diarrhea, vomiting, hemosiderosis, hemochromatosis, cirrhosis, diabetes, cardiac failure, increased incidence of hepatoma, and may compromise zinc and copper absorption. |
| Zinc | 15/12 mg | 15 mg | 19 mg | Gastrointestinal irritation, vomiting, impairment of copper status, microcytic anemia, impairment of immune responses, and decline in serum high-density lipoproteins. |
| Copper | 1.5-3.0 mgd | 2.0 mg | 100 mg | Usually due to accidental/intendual consumption of copper sulfate - get nausea, gastric pain, diarrhea, vascular collapse, and interacts with zinc, cadmium, and molybdenum in the body. |
| Fluoride | 1.5-4.0 mgd | None | 4 to 10 mg | 4 mg - mottling (chalkiness) of teeth; 10+ mg - adversely affects bone health, kidney function, and possibly muscle and nerve function. |
| Iodide | 150/150 mcg | 150 mcg | 2 mg | Blocks formation of thyroid hormones usually temporarily but can be permanent and may cause goiter. |
| Selenium | 70/55 mcg | None | 1 mg | Fingernail changes, hair loss, nausea, abdominal pain, diarrhea, fatigue, irritability, and peripheral neuropathy. |
| Manganese | 2.0-5.0 mgd | None | Unknown | Observed in individuals exposed to manganese dust, fumes, or contaminated well water - causes a severe psychiatric disorder, reproductive and immune system dysfunction, and kidney and liver disorders. |
| Chromium | 50-200 mcgd | None | Unknown | Observed in individuals exposed to chromate dust or absorption through the skin - causes increased incidence of lung cancer, dermatitis, and allergies. |
| Molybdenum | 75-250 mcgd | None | 10 mg | Antagonistic to copper and increased incidence of gout. |
| a1989 Recommended Dietary
Allowance for men and women (nonpregnant, nonlactating), 25-50 years of
age. Number to the left is for men and number to the right is for women.
Reference gives RDAs for other age groups. bUnited States Recommended Daily Allowance for adults and children 4 or more years of age. The U.S. RDA is used as a standard for nutritional labeling. The Food and Drug Administration has proposed changes in this labeling. cLowest reported toxic dose in publications considered to be reliable. dEstimated Safe and Adequate Daily Dietary Intakes; data are sufficient for estimating a range of requirements but not an RDA. eOther substances found in foods that have some vitamin-like functions; these nutrients are essential for some higher animals but not proved to be required by normal humans. |
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Table 1 also gives the lowest doses at which toxicities have been reported in reliable scientific publications. The literature contains many case studies where nutrient overdoses are presumed to affect health adversely. The nutrient amounts and time that people with toxicity problems took the nutrients are frequently not given so it is difficult to determine minimum toxicity levels. Size, age, sex, genetic background, as well as general health and previous nutritional status of individuals also affects responses to over consumption of vitamins and minerals.
Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Kenneth R. Bolen, Director of Cooperative Extension, University of Nebraska, Institute of Agriculture and Natural Resources.
University of Nebraska Cooperative Extension educational programs abide with the non-discrimination policies of the University of Nebraska-Lincoln and the United States Department of Agriculture.

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