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Vitamin and
Mineral Toxicities in Adults
by Judy A. Driskell,
Extension Foods and Nutrition Specialist
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.
Nutritional Status
People can have deficient,
adequate, or toxic intakes of any essential nutrient. A deficiency occurs when
the intake of the essential nutrient is too low to meet a person's need for
that specific nutrient. Adequacy occurs when a person gets enough, but not too
much, of a nutrient. Nutrient toxicity occurs when you get an overdose of a
given nutrient.
Causes of Nutrient
Toxicities
Most nutrient toxicities
don't occur from dietary intakes of foods. Vitamin toxicities usually come from
taking high potency vitamin supplements. Most mineral toxicities are a result of
inhalation.
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."
|
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. |
Symptoms of Toxicities
Table 1 gives the symptoms
of vitamin and mineral toxicities. Toxicities occur at lower intake levels in
infants, children, and pregnant and lactating women. If a woman takes
excessive amounts of many vitamins and minerals while pregnant her child can
be affected.
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 overconsumption of vitamins and
minerals.
Complications
Some nutrients have
specific pharmacologic effects at high dosages. Pharmacologic doses sometimes,
but not always, reduce symptoms of certain diseases and metabolic conditions,
and complicate the diagnosis of certain diseases. They also influence
treatment of some diseases and metabolic conditions. Medications may interact
with vitamins and minerals and influence medicine effectiveness.
Adaptation
Individuals can adapt to
taking large amounts of a vitamin or a mineral. And, if they stop taking high
levels of nutrient supplements and start consuming normal levels, they can
develop nutritional deficiency diseases (for example, scurvy). If one desires
to stop taking large doses of a vitamin or mineral, the intake should be
gradually decreased.
Legal Regulations
Some supplements have been
contaminated and some have failed to meet advertised claims. Because
supplements are legally considered to be foods not drugs, the Food and Drug
Administration has few regulations concerning them. Regulations are being
proposed on the marketing of high dosage supplements.
Selected References
Diet and Health --
Implications for Reducing Chronic Disease Risk. Washington, DC: National Academy
Press, 1989.
Handbook of Vitamins, 2nd ed.
New York: Marcel Dekker, Inc., 1991.
Modern Nutrition in Health
and Disease, 7th ed. Philadelphia: Lea & Febiger, 1988.
Present Knowledge in
Nutrition, 6th ed. Washington, DC: Nutrition Foundation, 1990.
Quantitative Evaluation of
Vitamin Safety. Pharmacy Times. May, 1985.
Recommended Dietary
Allowances, 10th ed. Washington, DC: National Academy Press, 1989.
Trace Elements in Human and
Animal Nutrition, 5th ed., volumes 1-2. San Diego: Academic Press, 1986.
Vitamin-Mineral Supplements and Their Usage by Adults. NebFact 92-90. August,
1992.
University of Nebraska
Cooperative Extension
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