Selenium

Imagine an antioxidant with the power to fight aging, halt heart disease, cut cancer rates, boost immunity, and speed healing. That’s selenium, one of the most important disease-fighting nutrients. Human and animal studies conducted over the past 40 years have shown that optimal intake of this trace mineral can help prevent heart disease, cancer and macular degeneration, slow cellular aging, reduce fat oxidation in the body, inhibit plaque formation in the arteries, and even halt the progress of HIV infection.

Once feared for its toxic effects, selenium has come a long way since 1957, when it was first found to prevent liver damage in animals deficient in vitamin E . The last of 40 nutrients to be proved essential to health, the Recommended Daily Intake (RDI) of selenium is 70 mcg for all men and women.

Selenium has many important functions within the body. As an antioxidant, it plays a major role in offsetting aging by preserving the elasticity of skin and preventing oxidative damage to fat cells. Selenium also serves as a building block in the formation of glutathione peroxidase, a powerful antioxidant enzyme produced within the body. Along with the enzymes catalase and superoxide dismutase (SOD), glutathione peroxidase is one of the body’s primary detoxifiers.

Natural levels of selenium in the blood decline with age, disease, dietary imbalances and excess amounts demanded by drugs or alcohol. Levels also depend on the availability of the amino acid glutathione, which is produced internally and consumed from foods, as well as on selenium intake. Without sufficient amounts of these two key nutrients, optimum levels of glutathione peroxidase can’t be produced, resulting in decreased disease-fighting resistance.

Preventing Disease

In recent years, studies have shown that people with higher blood levels of selenium are significantly less likely to develop many forms of cancer and heart disease than those with lower blood levels. Selenium’s protective effects on the heart stem from its ability to help block oxidation of low-density lipoprotein (LDL) cholesterol, which is a primary step in decreasing atherosclerosis, or plaque formation in the arteries. In arteries, oxidized LDL damaged by free radicals can combine with calcium and harden, forming plaque. In countries such as Finland, where low levels of dietary selenium have been linked to an increased risk of heart disease, supplementation with selenium, either via dietary supplements or through soil supplementation, has been found effective in increasing blood levels of selenium. Increased blood levels of selenium are associated with a reduced risk of cancer and heart disease.

Blood levels of selenium are directly linked to the amount of selenium consumed in the diet. For this reason, many Asian women are believed, in part, to have a lower incidence of breast cancer than their North American counterparts because their diet contains four times more selenium than the average North American’s. Asian women’s diets are also lower in overall fat, especially easily oxidized fats such as the polyunsaturated fats found in common cooking oils.

Selenium and Vitamin E

Selenium works synergistically with vitamin E, and supplementation with both is better than taking either alone. Many cancer and heart disease prevention studies have used a combination of these two nutrients to determine their effectiveness in curbing death rates.

For example, some of the world’s highest rates of esophageal and stomach cancer occur in north central China, where the Linxian cancer trials were done. Not surprisingly, the people in this area have been found to consume subadequate amounts of selenium as well as other nutrients. In the Linxian trial, completed in 1995, participants were put on either one of four supplement regimes or given a daily multiple vitamin/mineral supplement or placebo for more than five years. Of the group receiving one of four different supplement combinations (vitamin A and zinc; riboflavin and niacin; vitamin C and molybdenum; or beta-carotene, vitamin E and selenium), only the latter group showed significant reductions in total as well as fewer cancer-related deaths.

Selenium and AIDS

According to recent research, adequate levels of selenium may significantly slow the progression of HIV. Supplementation with selenium as well as vitamin E and other antioxidants has been shown to increase red and white blood cell counts in people with HIV, and it’s thought that some of the cardiac damage seen in HIV may be the result of low blood selenium levels. Adequate blood levels of selenium seem to contain the virus within infected cells because, in the presence of selenium, the virus makes a protein to repress its own replication. However, the virus also appears to slowly deplete the body of selenium. Therefore, when selenium levels get low, the virus can switch into a high rate of replication causing progression of HIV.

In a study completed last year, selenium deficiency was found to be an independent predictor of survival for those infected with HIV. Over three and a half years, 121 HIV positive men in Florida were assessed every six months for specific immunologic and nutritional factors believed to contribute to survival in HIV disease. Of the factors tested, CD4 cell count, antiretroviral treatment, plasma levels of vitamins A, E, B₆, and B₁₂ and the minerals selenium and zinc, only CD4 counts over time and selenium deficiency were significantly associated with mortality.

These results highlight the need for adequate selenium supplementation to prevent against low levels of selenium and glutathione, which is common in people with HIV. Low levels of these two nutrients are associated with inadequate production of glutathione peroxidase. Oxidative stress, the term used to describe damage caused by increased oxidation reactions in the body, causes tissue and cell damage and is believed to be one of the main factors causing disease progression and cell death in people with HIV. Increasing levels of all antioxidants, especially selenium and glutathione, is particularly important in people with HIV, who commonly have low blood levels of both these antioxidants.

Promoting Longevity

Nutrient-rich diets and supplementation with high levels of antioxidants including selenium are an essential part of all longevity regimes. As the human body naturally manufactures more antioxidants than most animals, antioxidant protection is seen as one reason why humans outlive other mammals. Evidence supports this link: numerous animal studies have shown dietary antioxidants can increase life spans and decrease cancer.

Selenium also appears to protect against cataract formation and macular degeneration, the leading cause of blindness in the elderly. Along with other antioxidants including vitamins C, E and beta-carotene, the human lens is protected by glutathione peroxidase. The selenium content in the human lens with a cataract is only 15 percent of normal levels. Several studies have shown that people with both macular degeneration and cataracts are usually lacking in one or more antioxidants. A National Eye Institute study showed that people with the highest intake of carotenoids had one-third the risk of developing macular degeneration as those who had the lowest intake. One carotenoid in particular, lutein, found in dark green leafy vegetables, is highly concentrated in the macula and is believed to provide the most free radical protection in this area of the eye.

How Much Do You Need?

The body doesn’t need much selenium per day. Yet the average "good" diet may contain only 35 to 60 mcg per day, and many doctors advise taking 200 to 400 mcg per day for good health. Though a little is great, a lot can be toxic. Exceeding doses of 700 to 800 mcg daily from all sources could be dangerous over time. However, excess intake is a rare problem in North America. Most North Americans, who rely on diets rich in processed foods, find it difficult to get enough selenium in the foods they eat.

Even those who eat plenty of protein foods, the richest sources of selenium, may find themselves consuming less selenium than they think. As food levels are dependent on soil quality, blood levels of selenium have been found to vary widely depending upon geographic location. Soil levels of selenium vary across North America, in part affected by soil depletion and intensive farming practices. Low soil levels translate to reduced selenium levels in livestock feed and other plant foods. This is a significant concern, for where blood serum levels of selenium are low, cancer rates increase. Where serum rates are high, cancer rates remain low.

The best food sources of selenium are grains and seafood (especially shellfish). Whole wheat flour and brown rice contain about 77 mcg of selenium per cup. Brazil nuts, especially those purchased in the shell, are one of the richest sources of selenium. Due to the quality of the Brazilian jungle soil, where the nuts are harvested, eating Brazil nuts in their shells is a great way to add selenium to your diet. One whole-shelled nut can contain as much as 100 mcg of selenium, whereas loose Brazil nuts contain approximately 12 to 25 mcg per nut (still a great deal). Meat also contains a lot of selenium.

Just a small amount goes a long way–there’s absolutely no reason to be selenium deficient!