Selenium: Important New Review of Health Findings

Selenium is a mineral which is essential in human nutrition in very small amounts (larger amounts are toxic). New research, much in the last five years, is finding that selenium deficiency may be involved in many important diseases, including HIV. The fact that this mineral has been the subject of irresponsible promotion as a cure-all must not blind us to the real possibilities that proper supplementation may have value in disease prevention and treatment.

A major literature review ⁽¹⁾ published this month in the Lancet offers a credible overview of what is known and not known at this time on selenium and human health. We were surprised by the strength of the case for more attention to supplementation as a possible treatment -- a medical intervention which would cost essentially nothing, so it could be available anywhere in the world.

Here are some quotes from the review (we did not include the references from the original). Note that all measurements are in micrograms, because of the very small amounts of selenium used in human nutrition -- about a thousand times less than the dose of most AIDS drugs.

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Concerning immune functions: "Supplementation with selenium, even in 'selenium-replete' individuals, has marked immunostimulant effects, including an enhancement of proliferation of activated T cells (clonal expansion). Lymphocytes from volunteers supplemented with selenium (assodium selenite) at 200 micrograms per day showed an enhanced response to antigen stimulation and an increased ability to develop into cytotoxic lymphocytes and to destroy tumor cells. Natural-killer-cell activity was also increased. Supplementation resulted in a 118% increase in cytotoxic-lymphocyte-mediated tumor cytotoxicity and an 82% increase in natural-killer-cell activity compared with baseline."

Concerning HIV: "Selenium seems to be a crucial nutrient for HIV-infected individuals. It is a potent inhibitor of HIV replication in vitro. . . More than 20 papers report a progressive decline in plasma selenium in parallel with the on-going loss of CD4 T cells in HIV-1 infection. This decline in selenium occurs even in early stages of disease when malnutrition or malabsorption cannot be a factor. In fact, plasma selenium is a strong predictor of the outcome in HIV infection. Baum and colleagues showed that selenium-deficient HIV patients are nearly 20 times more likely (p<0.0001) to die from HIV-related causes than those with adequate levels . . . Baum and colleagues showed that low plasma selenium is a significantly greater risk factor for mortality than low helper-T-cell count, by a factor of 16, and confers a more significant risk than deficiency of any other nutrient investigated."

Hepatitis: "Selenium also appears to be protective in individuals infected with hepatitis virus (B or C) against the progression of the condition to liver cancer."

Pancreatitis: "In a small controlled trial in Rostock, Germany, intravenous administration of selenium to patients with acute necrotising pancreatitis reduced mortality from 89% in controls to zero in the treatment group."

Cancer: Various studies have found more cancer or cancer deaths in persons with low selenium levels. For example, in a prospectively followed cohort of 34,000 men, "those in the lowest quintile [fifth] of selenium status, as measured by toenail selenium, were found to have three times the likelihood of developing advanced prostate cancer as those in the highest quintile (p for trend=0.03). Only cases diagnosed more than 2 years after collection of the samples were counted." [The reason for not counting earlier cases is to avoid confusion due to the possibility that the illness itself might cause the low selenium levels through poor intake, absorption, or metabolism of food.]

Other research has found effects of correcting selenium deficiency on mental status, tiredness, and mood -- and possibly on cardiovascular disease, although findings here have been mixed, perhaps because some of the trials included very few people with selenium deficiency.

And a warning: "We must be careful not to encourage over-consumption of selenium supplements. While an intake of selenium of around 15 micrograms/kg bodyweight per day is thought to be without prolonged impact on human health, it must be remembered that selenium is a toxic mineral with a fairly small therapeutic window. In some sensitive individuals, the maximum safe dietary intake may be as low as 600 micrograms per day. It would therefore seem prudent to restrict adult intake from all sources to an upper limit of 400-450 micrograms/day as recommended by several expert panels."

Persons considering supplementation should note that the multivitamins they are taking may already include selenium -- in addition to their dietary intake, which tends to be higher in the U.S. than in many countries.

Comment

There is no clear agreement on how to supplement with selenium -- exactly who should use it, how much, or in what form. (In the research, selenium has been supplied both as inorganic forms such as selenate or selenite, and organic forms such as selenomethionine, or as selenium yeast.) Trials are ongoing, including at least two in HIV. But major uncertainties will remain.

We need more attention on rational ways to make decisions based on the incomplete information available now. Most professionals like to have definite proof, and are reluctant to prepare guidelines or recommendations based in part on reasonable guess. The frequent result is recommendations which are much too conservative, or none at all -- leaving the field to self-medication and a few self-taught experts, or to medical promoters or cultists. There should be widely discussed nutritional guidelines for persons with HIV, updated at least once a year -- as with guidelines for antiretroviral drug therapy.

Selenium levels in diet vary greatly by geography, because of the different amounts of the mineral in the soil where crops are grown. For example, diets are deficient in many areas of Western Europe, and of Africa. (Finland was especially deficient, and supplemented its food supply by adding selenium to fertilizer starting in 1984). It seems possible that region-specific, sophisticated recommendations on nutritional and other low-cost interventions could make major, cost-effective contributions both to treatment and prevention, benefiting those already infected and slowing the spread of the epidemic.

References

1. Rayman MP. The importance of selenium to human health. Lancet. July 15, 2000; volume 356, pages 233-241.

ISSN # 1052-4207

Copyright 2000 by John S. James. Permission granted for noncommercial reproduction, provided that our address and phone number are included if more than short quotations are used.

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