|
|
SELENIUM SUPPLEMENTATION
We know the healthy U.S.
recommended dietary allowance (RDA) for selenium intake is 55 µg/day
for men and women over the age of 19 years. (67) Yet, current RDAs
may not reflect true requirements, which can vary depending upon dietary
intake and physiological state. The average daily intake of selenium from
foods in the United States is about 100 µg.
Ingestion of excessive
amounts of selenium can result in various conditions (Table
3). (2, 4, 5, 68) Schrauzer and Sacher note continuous administration
of selenium at high doses (1 mg/day) can have an immunosuppressive effect
and increase the release of tumor necrosis factor alpha or other inhibitors
associated with the processes leading to CD4 T-cell depletion. (69)
Considerably more information is available on animal toxicity than human
toxicity. However, selenium-induced lesions among all species are similar,
illustrating a positive corollary for selenium effects in both animals
and humans. Epidemiological data from China describe a syndrome of selenium
toxicity manifested by cracked fingernails and extensive hair loss. (70)
The Lowest-Observed-Adverse-Effects-Level (LOAEL) for selenium in adults
is 900 µg daily; intakes of selenium less than 900 µg/day (for
adults) are unlikely to result in selenium toxicosis. The selenium upper
intake limit however, is set at 400 µg/day. The toxicity
of selenium depends upon the chemical form of selenium ingested and upon
the selenium levels in the foods consumed. There are no known interactions
with drugs in clinical practice. Interactions may occur, however, with
other nutrients such as the potentiation of antioxidant activity of tocopherols
and decreased selenium bioavailability in the presence of vitamin C. (71) |
|
|
Recommendation: Taylor
notes, "...supplementation is likely to be necessary and beneficial, at
least in some cases". (2) Even though it seems advisable to consider
some level of supplementation, patients should consult with their doctors
before adding selenium to their daily regimen. Since few studies report
on dietary intake of selenium, it is difficult to assess the extent to
which the decreased selenium status of PLWHIV is due to dietary intake
or metabolic changes associated with HIV-infection. Based upon reported
correction of selenium deficiency at doses of 100 to 500 µg selenium
supplementation daily and the ability of these doses to restore antioxidant
function in PLWHIV and influence clinical outcome, it is reasonable to
suggest selenium supplementation in PLWHIV should be 100 to 200 µg/day.
A dose of 400 µg/day seems reasonable for patients with impaired
absorption. (2) Taking up to 800 µg/day for a few weeks to
get blood levels up, followed by 400 µg/day seems reasonable for
those demonstrably deficient in selenium. It is best to take selenium with
a good multivitamin to help offset imbalances that may occur in other trace
minerals. |
|
