At present, there is no convincing evidence that vitamin and mineral supplements positively impact on progression of disease or death in people with HIV. No well-controlled studies have examined the relationship between supplements and disease in people with HIV. Universal recommendations for specific supplementation regimens in people with HIV are, therefore, based on speculation and uncontrolled anecdotes.
The presence of a vitamin or mineral deficiency does not imply that supplementation will correct it. Deficiencies may be caused by many factors, including some which may not respond to supplementation. HIV-induced metabolic changes or malabsorption can result in vitamin deficiency, although they will not respond to supplementation. Importantly, several studies demonstrated vitamin and mineral deficiencies in people with HIV although the subjects ate properly and, in some cases, even took supplements. Furthermore, correct vitamin and mineral doses are not been established to correct specific levels of deficiency.
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Beneficial claims are frequently for very large doses of
vitamins ("mega-dosing"), often hundreds or thousand times higher than nutritionally required levels. Using vitamins in this manner is more similar to drug therapy than
nutrition, and should be considered in pharmacological terms. Some "mega-doses" of vitamins may have legitimate pharmacologic uses, although none have been demonstrated for HIV disease. Certain vitamins, like Vitamin A and Vitamin D, produce very serious toxicities not far above their nutritionally required levels. Other vitamins, like Vitamin E, appear to have no upper limits for safe consumption. See
Table II.
Vitamin A (and beta-Carotene -- a pro-vitamin that is converted into vitamin A by the body), first discovered in 1915, is found in both animal and plant products. Vitamin A has a role in many physiological functions, including reproduction, skin, vision, the immune system, and bone. Vitamin A deficiency can cause numerous non-specific signs, although nyctalopia and xerophthalmia (two diseases of the eye) are the best described syndromes. Vitamin A deficiency is considered extremely rare in the developed world because many common foods, including margarine, are fortified with the vitamin, and because the body can store Vitamin A successfully in the liver and intestine for long periods of time, compensating for periodic deficiencies. Diseases associated with vitamin A deficiency occur only after prolonged periods of deprivation.
Table II: Vitamin Toxicities
| Vitamin A |
Vitamin A may be the most toxic vitamin. Its threshold for safe intake is quite small compared to other vitamins. Toxicities have been reported at levels as low as 25 times the RDA. Most toxicities appear to occur after consumption of 25,000 to 50,000 IU per day for several months. Birth defects have been noted when pregnant women consume more than 25,000 IU per day. Signs of vitamin A toxicity include: loss of appetite, weight loss, bone malformations, spontaneous fractures, and internal bleeding. These toxicities can be reversed when the vitamin is discontinued. |
| Vitamin D |
Vitamin D is also a very toxic vitamin. Adverse reactions have been reported after single overdoses as low as 50 times the RDA. Overzealous fortification of infant formula with vitamin D in Britain in the 1950s resulted in Vitamin D toxicities in many children. Vitamin D toxicity causes bone lesions. |
| Vitamin E |
There is little data, but the toxic potential of this vitamin appears very low. Intake over 100-times the RDA for several months results in no toxicities. |
| Vitamin K |
This vitamin does not appear toxic at any dose in humans when given orally. Intravenous administration of Vitamin K at doses of 2 to 8mg/kg is lethal in horses, however. |
| Vitamin C |
This vitamin is moderately toxic. Intake at 20 to 80 times the RDA produces gastrointestinal disturbances and diarrhea. People with a history of calcium oxalate kidney stones should consult a physician before taking high doses of this vitamin. |
| Thiamin |
Thiamin has a low toxicity when given orally. Intravenous doses at 100 to 200 times the RDA has caused intoxication in humans, involving headache, convulsions, muscular weakness, paralysis, and cardiac arrhythmias. |
| Riboflavin |
No riboflavin toxicities have been reported in humans at any dose. |
| Niacin |
The toxicity of niacin may be related to the chemical form in which it is consumed. Nicotinic acid can cause itching, nausea, vasodilatation, and vomiting in humans at doses of 2 to 4g/day. Nicotinamide only rarely produces these toxicities and is the preferred medical form of the vitamin. |
| Vitamin B-6 |
This vitamin causes toxicities only at high doses given over long periods. Doses of 500mg to 6g/day can cause reversible neuropathies in humans. |
| Pantothenic acid
|
No toxicities have been reported with pantothenic acid in humans. When given intravenously, this vitamin can be lethal in rats at doses of 1g/kg. |
| Biotin |
No toxicities have been reported in humans at any dose. |
| Folate |
High doses of folate in humans are associated with reduced zinc absorption. No other toxicities have been established for any dose. |
| Vitamin B-12 |
This vitamin is considered non-toxic, but rare B-12 allergic reactions have been reported in humans. |