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May 9, 2000

A Critical Analysis of The National Academy of Sciences' Attack on Dietary Supplements

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What They Said About Selenium


Selenium is a mineral used to protect against a wide range of diseases, but the authors of the book only discussed the role of selenium as an antioxidant and cancer preventive agent.

The authors omitted from discussion studies showing selenium protects against heart disease,(167-197) studies showing selenium protects against hepatitis viral damage,(198-206) studies showing selenium slows progression of HIV,(207-224) studies showing that selenium protects against cataract,(225-234) and numerous other studies showing definitive health benefits in humans.(235-273) These studies were omitted as if they did not exist.

Here is what the 512-page book did report about studies on selenium and cancer on pages 290-291:

"Subjects assigned a daily combination of selenium (50 mcg), beta-carotene (15 mg) and vitamin E (30 mg) achieved a significant (21 percent) decrease in gastric cancer mortality, resulting in a significant 9 percent decline in all-cause mortality. However, these results cannot be attributed to selenium alone, because the individuals consumed selenium in combination with beta-carotene and vitamin E."

"200 mcg a day of selenium administration in the form of yeast showed no effect on recurrence of non-melanoma skin cancer compared to placebo group but significantly lower rates of prostate, colon and total cancer were observed among those assigned to the selenium group." (This was considered a negative study by the authors)

"The risk of prostate cancer for men receiving 200 mcg a day of selenium was one-third that of men receiving placebo."

While numerous published studies exist to support the protective role of selenium against cancer, the authors choose only the above three studies to question the value of selenium supplementation. The three studies cited above, however, are quite positive, yet the authors twisted their meaning to imply the studies showed no definitive cancer risk reduction benefit.

As far as cancer and selenium are concerned, the 512-book concluded with the following information on page 291:

"Results of these three studies are compatible with the possibility that intakes of selenium above those needed to maximize selenoproteins have an anti-cancer effect in humans. These findings support the need for large-scale trials. They cannot, however, serve as a basis for determining dietary selenium requirements at this time."

The overriding error with the above “conclusion” is that it failed to incorporate the findings of a large-scale clinical study published in the December 25, 1996 issue of the Journal of the American Medical Association showing that compared to placebo, those people receiving a 200 mcg supplement of selenium had a 37% reduced risk of cancer incidence and a 50% reduction in cancer mortality. This 9-year study is exactly what the authors of the book said needed to be done to validate the anticancer benefits of selenium. The fact that this positive and well recognized study was omitted seriously questions the credibility of this 512-page book.

The authors omitted studies indicating that selenium may be effective as an adjunctive cancer therapy. One study(274) showed that when rats with mammary tumors where given moderate doses of supplemental selenium, a significant inhibition of cancer-associated angiogenesis occurred. Tumors require new blood vessels to sustain their rapidly proliferating cancer cells. Substances that inhibit the formation of new blood vessels are called antiangiogenesis agents, and these substances are being extensively studied as potential cancer therapies. Selenium’s anti-angiogenesis property may be one reason why is has been shown to reduce cancer mortality rates in humans already diagnosed with cancer.

In Germany, selenium is being used as an adjunctive cancer therapy. In a study(275) omitted from the 512-page book, German doctors evaluated the effects of selenium supplementation in women with breast and gynecological cancers. Here is a summary of their findings:

"In pilot studies with low-dose selenite (up to 300 micrograms a day) the patients reported a better quality of life. Side effects were not reported. Analysis of the immune system reveal a stimulation of B19 lymphocytes and natural killer cells. In Germany, a country with selenium deficiency, clinical studies are now carried out on the effects of selenium as a drug to reduce side effects of chemo- and radiotherapy, enhance quality of life by reducing toxic side effects and help to restore immune function."

Another study that was omitted from the 512-page book showed that rectal cancer patients treated with radiation and chemotherapy benefitted from high dose selenium supplementation. In this study, 2000 micrograms of selenium were given after every course of chemotherapy and 400 micrograms of selenium given daily during irradiation. The doctors were able to verify a protective effect and concluded that “oral selenium intake in rectal cancer patients is easily tolerated with no side effects.”(276)

Another study(277) omitted from the 512-page book measured serum levels of selenium in those diagnosed with colon cancer. The results of this study showed that colon cancer patients with low serum levels of selenium had significantly shorter survival time compared to patients with higher selenium levels. In a related study(278) also omitted from the 512-page book, patients with colorectal cancer or adenoma had very low serum selenium levels compared to age-matched healthy controls. The doctors conducting this study stated:

"These results indicate that low selenium status is strongly associated with colorectal neoplasia (including extension and severity of the disease) and that it may not only be a result but also one of tumorogenic factors. That means that selenium supplementation could be important in prevention or even adjuvant therapy of colorectal cancer."

Another significant study(279) sponsored by the National Cancer Institute, (but omitted from the 512-page book) showed that the combination of selenium and vitamin E or the combination of n-acetyl-cysteine and vitamin A analogs may be effective in protecting against lung cancer.

Another omitted study(280) reviewed the molecular mechanisms of selenium’s actions in the body and concluded that:

"Higher levels of selenium supplementation can be expected to affect other functions related to tumorigenesis: carcinogen metabolism, immune function, cell cycle regulation and apoptosis. Thus, according to this 2-stage model of the roles of selenium in cancer prevention, even individuals with nutritionally adequate selenium intakes may benefit from selenium supplementation."

Despite questioning the health benefits of selenium, the authors of the 512-page book increased the maximum safe daily amount of selenium intake to 400 mcg per day. Many vitamin takers, of course, have been consuming 400 mcg a day and higher of selenium for decades without evidence of toxicity (selenosis). Since published studies show 200 mcg a day of selenium results in significant (up to 50%) reductions in cancer mortality,(281-288) one might think the recommended allowance would be increased to 200 mcg a day, but that was not the case. Instead, the authors concluded the following on page 319:

"Limited evidence has been presented that intakes of selenium greater than the amount needed (55 mcg) to allow full expression of selenoproteins may have chemopreventive effects against cancer. Controlled intervention studies are needed to fully evaluate selenium as a cancer chemopreventive agent."

The problem with the above conclusion is that only “limited evidence” was presented in the book about selenium’s health benefits, as the authors omitted most of the positive published studies showing that selenium prevents cancer and is effective in treating and preventing many other diseases.

Selenium may even reduce the incidence of heart attack. Another study(180) omitted from the book involved 3387 men aged 53-74 followed over a three year time period. Men with the low serum levels of selenium had a 70% greater risk of coronary heart disease compared to those men with higher selenium levels, and this finding was independent of other risk factors. However, not all studies are consistent. A five-year study(192) of 1,110 men aged 55 to 74 years showed that the risk of stroke was 3.7 times greater in the low selenium group compared to the high selenium group. However, in this same study, high selenium levels did not produce a statistically significant reduction in the rate of heart attacks. So selenium was shown to protect against heart attack in one study, and stroke (but not heart attack) in another study. Since these findings are inconsistent, the authors do not recommend people supplement with selenium.

One finding that shows up repeatedly is that adults living in selenium deficient geographic areas have severely reduced life spans. Heart muscle damage is common at autopsy in these selenium-deficient cases. In 25 cities in the United States, low selenium correlates with high rates of heart attack and cancer.177 In trying to understand the mechanisms by which selenium protects against heart disease, scientists have looked at the effects of selenium in protecting the enothelial lining of the arterial system against oxidative damage, protecting blood cells against abnormal aggregation, and by inhibiting LDL cholesterol oxidation. Moreover, selenium prevents toxic effects of cadmium and mercury, and helps to modulate the active transport of calcium out of the arterial system.(183)


One study(186) pointed out that human platelets need selenium to create an important antioxidant enzyme called glutathione peroxidase. Platelets of selenium-deficient subjects show increased aggregation, thromboxane B2 production and synthesis of the lipoxygenase-derived compounds. In these deficient subjects, selenium administration increases platelet glutathione peroxidase activity and inhibits platelet hyperaggregation and leukotriene synthesis. In addition to its potential effects in protecting against cardiovascular events, selenium appears to protect the body against damage caused by hepatitis B, hepatitis C and HIV. In one study on HIV patients(191) selenium deficiency was associated with myopathy, cardiomyopathy and immune dysfunction including oral candidiasis, impaired phagocytic function and decreased CD4 T-cells.

The book omitted any information relating to the role of selenium in preventing cataract. One of these omitted studies(226) showed that when supplemental selenium was given along with beta-carotene and vitamin E, there was a statistically significant 36% reduction in the prevalence of nuclear cataract. The book omitted any reference to the protective effect selenium confers against primary liver cancer and infection with the hepatitis B or C virus. One notable study that was omitted(198) involved a staggering 130,471 people followed for eight years. The group who received supplemental selenium had a 35.1% reduction in the incidence of primary liver cancer compared to the placebo group which did not receive selenium. When selenium supplementation was discontinued, incidences of primary liver cancer began to increase, indicating that continuous intake of supplemental selenium is essential to sustain its protective effect against liver cancer. In a sub-group of this study that evaluated 113 patients infected with the hepatitis B virus, the daily intake of 200 mcg of selenium resulted in zero rates of liver cancer, compared to 7 liver cancers in the placebo group (not receiving selenium supplements). When the selenium group stopped taking the selenium supplement, primary liver cancer rates began to increase.

Another omitted study(289) examined the association between plasma selenium levels and risk of hepatocellular carcinoma among chronic carriers of hepatitis B and/or C virus in a cohort of 7,342 men. This 5.3 year study showed that those with low blood selenium levels were 47% more likely to develop hepatocellular carcinoma (primary liver cancer) compared to those with higher levels of selenium.

Also omitted was a small case history report(290) showing substantial benefit to treating advanced hepatitis C patients with a combination of alpha lipoic acid, silymarin and selenium. Here is what the physician reported regarding his clinical observations:

"The triple antioxidant combination of alpha-lipoic acid, silymarin and selenium was chosen for a conservative treatment of hepatitis C because these substances protect the liver from free radical damage, increase the levels of other fundamental antioxidants, and interfere with viral proliferation. The 3 patients presented in this paper followed the triple antioxidant program and recovered quickly and their laboratory values remarkably improved. Furthermore, liver transplantation was avoided and the patients are back at work, carrying out their normal activities, and feeling healthy."


The physician noted that supplementation with these three nutrients is relatively inexpensive compared to more than $300,000 for liver transplant surgery. He also noted that other problems with liver transplant surgery include a shortage of available livers, reinfection of the new liver with residual virus, and high mortality rates associated with the procedure including greater risks of cancer from the immune-suppressing drugs given to suppress organ rejection.

In another omitted study,(291) when selenium, n-acetyl-cysteine and interferon were used to treat hepatitis C, selenium and n-acetyl-cysteine showed no enhanced effect compared to interferon alone. When 544 IU a day of vitamin E was added to the selenium, n-acetyl-cysteine and interferon group, however, complete response occurred in six out of eight patients. Compared to the group receiving interferon alone, the group obtaining the vitamin E, selenium, n-acetyl-cysteine and interferon showed a 2.4 greater chance of obtaining a complete response and had a significant reduction in viral load. This study helps substantiate the need to use multiple antioxidant nutrients in treating disease. While selenium by itself has been shown to protect against hepatitis-induced liver cancer, this study showed the importance of adding other antioxidants (vitamin E and n-acetyl-cysteine) to put active hepatitis infection into remission when combined with interferon.(300)

Yet another omitted study(206) involving 20,847 people showed that those supplementing with selenium showed a 70% reduction in becoming infected with the hepatitis B virus compared to surrounding populations not receiving supplemental selenium.

Numerous published studies demonstrate a molecular basis for how selenium may protect against hepatitis infection and subsequent development of liver cancer, yet the authors of the 512-page book chose to omit this plethora of research as if it did not exist.

Selenium has shown efficacy in slowing the progression of HIV infection. One study(207) showed that low plasma level of selenium in children with AIDS is an independent predictor of mortality, and appears to be associated with faster disease progression. This study showed increased mortality greater than 5-fold in children with low selenium levels. Another study(292) found that selenium deficiency is an independent predictor of survival in adults with HIV-1 infection. These two studies were omitted from the 512-page book.

Also omitted was a study(210) indicating that supplementation with selenium may help to increase the enzymatic defense systems in HIV-infected patients and slow disease progression.

In a study(213) funded by the FDA, supplemental selenium was shown to have a positive effect in boosting various immune parameters that are suppressed by the HIV virus. The doctors conducting this study stated:

"Taken together, these results suggest that selenium supplementation may prove beneficial as an adjuvant therapy for AIDS through reinforcement of endogenous antioxidative systems."

The sheer volume of studies showing selenium to be an effective adjunctive therapy against HIV infection is overwhelming, but none of these studies were reported on in the 512-page book. Its not just people infected with the HIV virus who are immune compromised. A pioneering study published in The Lancet(293) found that seniors taking modest doses of a multivitamin/ multimineral supplement containing zinc and selenium showed a general reduction in infection and required antibiotics for significantly fewer days. A more recent study brings the effect of these two minerals into sharper relief. This well-designed study (randomized, placebo-controlled, double-blind) found that seniors taking zinc and selenium had significantly fewer infections over a two year period, but that vitamin supplementation alone did not have a major effect.(294) The zinc and selenium supplement cut the number of infections by nearly two thirds compared to placebo. A follow-up study demonstrates that seniors supplementing with zinc and selenium show improved antibody response to the flu vaccine.(268)

Despite the enormous health benefits that selenium supplementation has been shown to confer in humans suffering from chronic disease or normal aging, the authors omitted these studies from the 512-page book, which would lead people suffering from these diseases to believe there is no value in taking supplemental selenium.

While the authors increased the safe total daily intake of selenium to 400 mcg and cited a few of the studies showing selenium may prevent cancer, the authors’ “conclusion” is that 55 mcg a day from diet is adequate. This “conclusion,” recommending only 55 mcg of selenium a day, contradicts the published studies showing that 200 mcg a day from supplemental selenium confers protection against the development of cancer and other diseases.

The authors stated that “insufficient evidence” existed to warrant selenium supplementation for the prevention of cancer, yet the authors omitted most of the positive evidence showing that selenium is effective in preventing cancer.

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