Herbs, supplements and HIV

January 2005 View PDF En español

Vitamins and potential side effects

Vitamin A and beta-carotene	Perhaps the most toxic vitamin. At high doses (more than 25,000 IU per day) toxicities are more likely, including loss of appetite, weight loss, bone malformations, spontaneous fractures, internal bleeding, liver toxicities and birth defects.
Vitamin B-6 (pyridoxine)	Reversible neuropathy has been reported in people taking high doses (500mg to 6 grams a day) over extended periods of time. For people with previous side effects associated with taking higher doses, symptoms resumed at doses as low as 50mg per day. (NOTE: The recommended daily allowance of this vitamin is 2mg per day.)
Vitamin B-12	In very rare instances, allergic reactions have been reported.
Folate	High doses have been associated with reduced zinc absorption and have been shown to mask signs of vitamin B-12 deficiencies. Vitamin C High doses can cause diarrhea and gastrointestinal distress. Buffered formulas are available and may decrease stomach problems. People with a history of kidney stones should consult a doctor before taking high doses.
Vitamin C	High doses can cause diarrhea and gastrointestinal distress. Buffered formulas are available and may decrease stomach problems. People with a history of kidney stones should consult a doctor before taking high doses.
Vitamin D	Potentially very toxic, can cause bone lesions. Toxicities reported with a single high dose supplement.
Thiamin	Very high intravenous doses have caused intoxication, headache, convulsions, muscular weakness, paralysis and cardiac arrhythmias.
Biotin	No reported toxicities.
Vitamin E	At doses higher than 1,000mg (1,500 IU) it can interfere with blood clotting. Prolonged use of high doses (800-3,200mg/daily) has been associated with nausea, diarrhea, muscle weakness and fatigue.
Riboflavin	No reported toxicities.
Pantothenic Acid	No reported toxicities in humans.
Vitamin K	No reported toxicities at doses of up to 500 times the required daily allowance (0.5mg/kg/day).
Niacin	Toxicities may be related to formulation. Nicotinic acid can cause itching, nausea, diarrhea and vomiting at doses of 2 to 4 grams/day. Nicotinamide only rarely produces these toxicities. At high doses, less common but more serious side effects may include liver injury, muscle disease, vision problems, low blood pressure, heart disease and poor blood clotting.