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Vitamin A: Chronic daily vitamin A intakes in excess of 10,000 IU or weekly intakes in excess of 25,000 IU have resulted in hypervitaminosis A. Early signs of hypervitaminosis A include fatigue, lethargy (lack of energy), irritability, malaise/depression, loss of appetite, abdominal pain/discomfort, nausea and vomiting, mild fever, and excessive sweating. Treatment of hypervitaminosis A consists of discontinuance of vitamin A and supportive therapy as indicated.
Other symptoms of vitamin A toxicity include blurred or double vision, dizziness, drowsiness, headache, insomnia, lack of muscle coordination, seizures, papilledema, raised intracranial pressure; bulging fontanelle (in infants), hypercalcemia (due to increase in activity of alkaline phosphatase), bone and joint pain, rapid resorption of bone/hyperostosis, osteoporosis, osteosclerosis, skin disorders (dermatitis, dryness, pruritus/itching, redness, scaliness, skin peeling, rash), cracking of the lips, loss of hair, diarrhea, weight loss, cessation of menstruation in women, and liver damage, which in turn leads to jaundice.
Not all signs appear in all patients, and relative severity varies widely among different individuals. Most signs and symptoms disappear within a week, but skin and bone changes may remain evident for several months.
A long term study also suggests that high intake of vitamin A (≥2,000 mcg of retinol per day) is related to increased risk of hip fractures in older women.
Excessive vitamin A intake (more than 10,000 IU daily) is hazardous when taken during the first and second trimesters of pregnancy. Excessive vitamin A intake during pregnancy may lead to birth defects such as cleft palate, heart abnormalities and brain malformations, e.g., hydrocephalus and microcephaly (baby with a very small head).
Vitamin C: Prolonged intake of ascorbic acid (vitamin C) in excess of 2 g per day may lead to nausea, abdominal cramps, diarrhea, and nose bleeds. Elevated serum glucose levels, GI obstruction, and esophagitis have also been reported in those taking high oral doses of vitamin C.
In people with kidney disease, excess vitamin C also may contribute to oxalate-containing kidney stones. In healthy people, epidemiological studies do not support an association between excess vitamin C intake and kidney stones. High vitamin C intake may also boost iron absorption - useful for some, but problematic for people with hemochromatosis, a metabolic disease that cause excess iron accumulation.
Vitamin E: There are no available data on acute overdosage with vitamin E. However, large doses have occasionally been associated with side effects (see Adverse Reactions).
Selenium: Prolonged intakes of selenium (doses of 1,000 mcg or greater daily) may lead to selenosis. Symptoms include fatigue, irritability, garlic-like breath odor, GI upset, nausea, vomiting, hair and nail brittleness and loss; skin rash, tooth decay, mild nerve damage, and hyperreflexia (overresponsive reflexes).
Zinc: Signs of acute zinc toxicity (doses >200 mg daily) include GI pain/cramps, nausea, vomiting, and diarrhea, loss of appetite, headache, lethargy, muscle pains, and fever.
Prolonged zinc supplementation may cause impairment of copper and iron status, and anemia at doses >50 mg/day; immune deficiency, reduced blood high-density lipoprotein (HDL) levels, and gastric erosion at doses >150 mg daily.
Long-term (average 6.3 years) ingestion of supplemental zinc (80 mg/day) has also been linked to a significant increase in hospitalizations for urinary tract infections and kidney stones.
Lecithin: Nausea, diarrhea, and increased salivation have been occasionally reported with the use of lecithin in doses >3.5 g per day.
