Why We Age - Anti-aging and Life Extension

Definition of Selenium

Selenium is an essential trace element. It is an integral part of enzymes, which are critical for control of the numerous chemical reactions involved in brain and body functions. Selenium has a variety of functions. The main one is its role as an antioxidant in the enzyme selenium-glutathione-peroxidase. This enzyme neutralizes hydrogen peroxide, which is produced by some cell processes and would otherwise damage cell membranes.
Selenium also seems to stimulate antibody formation in response to vaccines. It also may provide protection from the toxic effects of heavy metals and other substances.
Selenium may assist in the synthesis of protein, in growth and development, and in fertility, especially in men. It has been shown to improve the production of sperm and sperm motility.  http://www.nlm.nih.gov/medlineplus/ency/article/002414.htm

Sources of Selenium

• Red meat
• Fish such as Tuna and Cod
• Shellfish
• Garlic
• Chicken and Turkey
• Eggs
• Sometimes vegetables (if grown in selenium rich soil)
• Certain nuts, including Brazil and Walnuts
• Cheese
• Long grained brown rice
• Oatmeal

Recommended Daily intake of Selenium

Effects of reduced levels of Selenium

Selenium is an essential trace mineral, however at levels of over 1200 mcg (inorganic Se) or 3500 mcg (organic Se) it can be toxic. There is some evidence suggesting that selenium by itself does not cause illness. Instead it is theorised that a deficiency of selenium makes the body more susceptable to illnesses caused by a variety of infections agents and nutritional or biochemical deficiencies.

Three diseases have been linked with a deficiency in selenium. these are:

• In selenium deficient children Keshan disease can occur.  This results in an enlarged heart together with a general degradation in the functioning of this organ.  This disease was first identified in China in the 1930’s and is still seen in rural areas of China where the soil is particularly deficient in selenium
• Myxedematous Endemic Cretinism.  The result of this condition is mental retardation
• Kashin-Beck disease.  This results in osteoarthropathy (a disease affecting the joints and bones)

Effects of too much Selenium

Overdosing on selenium can result in a condition called Selenosis. The symptoms of this disease include gastrointestinal damage, garlic smelling breath, low grade nerve damage, fatigue, irritability and hair loss. Overdosing on selenium is however rare and is usually associated with such things as industrial accidents resulting in environmental contamination or (as in one American case) an excessively high level of selenium produced in a dietary supplement. 400 micrograms per day is generally considered the maximum safe dosage of selenium to take.

Anti-aging and general benefits of Selenium

A number of studies involving selenium have shown that it may help to protect against such wide-ranging conditions as cancer, heart disease and arthritis. Below is a summary of the research so far:

Selenium and cancer

A study released by the Division of Nutritional Sciences, Cornell University, Ithaca, New York involved 1312 patients who had a history of basal/squamous cell carcinomas of the skin. These patients were recruited between 1983-1990 and were assigned randomly into two groups. One group was given a daily oral supplement of selenium-enriched yeast (200 micrograms), the other group was given a low-selenium yeast placebo. The study was conducted in a double-blind manner and plasma selenium concentrations were determined at intervals of 6-12 months. Any illnesses reported by the patients were recorded, together with any development of cancers or deaths.

Selenium intake did not seem to affect significantly the recurrence of basal/squamous cell carcinomas of the skin. High selenium plasma concentrations did however correlate with a reduction in the incidence of other cancers, including prostate cancer, lung cancer and colorectal cancer. There was also a reduced rate of mortality in patients who had been taking the selenium supplements compared with those who had recieved the placebo.

For further information on this study, visit Cornell Selenium study

Selenium and heart disease

There have been a number of population studies that have shown links between low intakes of antioxidants (including selenium) and an increased incidence of heart disease. It has also been theorised that increased levels of free radicals in the body contribute to heart disease. Basically cholesterol is transported in the bloodstream from the liver to the tissues of the body in the form of Lipoproteins. Low density lipoproteins (LDL's) can become oxidised and seem to play a part in the development of atherosclerosis, a condition were the arteries and medium-sized blood vessels become clogged and harden. This can lead to heart attacks, strokes as well as kidney and eye problems. Note that High density lipoproteins (HDL's) deposit cholesterol in liver were it is then excreted from the body.

It has been postulated that selenium may help to prevent the oxidation of LDL and thus reduce the chances of developing heart disease.

Selenium and arthritis

Our immune systems produce free radicals in order to destroy invading microorganisms and also to break down damaged tissue. Unfortunately however, these same free radicals can also cause damage to healthy cells and tissues. Rheumatoid arthritis is a painful chronic condition that results in swelling, stiffness and a loss of functionality of the joints. A number of surveys including one conducted by the Social Insurance Institution, Helsinki, Finland have shown that sufferers of rheumatoid arthritis have reduced blood levels of selenium. Although research is still inconclusive, it may be possible that selenium supplements may help to eleviate some symptoms of this condition by neutralising free radicals.

For more details of how selenium plays a role in scavenging free radicals in cells and tissues, see Glutathione peroxidase

Mark S D'Arcy