Selenium is a little-known mineral that has the potential to play an important role in our health. Some research has provided hints about the functions of selenium and some supplements have started to include this trace mineral, but many people still don’t really know what it does! However, more knowledge now shows that a small amount of selenium in our diet could make all the difference in our general and hormonal health.
What is selenium?
Selenium is actually a trace mineral found in soil. It is called a “trace mineral” because it is only found in small amounts and the body also requires very little of it. Even though it is only needed in small amounts, it is essential for many body processes and is present in nearly every cell, particularly in the kidneys, liver, spleen, testes and pancreas. One of selenium’s main functions is to act as an antioxidant against free radicals that damage the DNA in our cells. Free radicals are believed to be molecules that promote inflammation and contribute to ageing and degenerative diseases like cancer, arthritis, atherosclerosis and Alzheimer’s disease. Due to these antioxidative properties of selenium, it actually has a crucial impact on our general health and the development of many diseases.
Functions of selenium
Selenium is often included with vitamin C and E in dietary supplements to strengthen the immune system and protect against viral infections. Some research has shown that selenium can fight the herpes virus that can cause genital sores and shingles. What’s even more amazing is the potential role that selenium may play in reducing the progression of HIV to AIDS by slowing down the replication of HIV in the body. One study found that AIDS patients with low levels of selenium were 20 times more likely to die from an AIDS-related illness than those with healthy levels of the mineral. Researchers are now studying whether selenium could one day be part of HIV treatment.
A research article published in The Lancet in 2000 also highlighted the potential of selenium to reduce the risk of thyroid problems, pregnancy and fertility problems, heart disease and even the progression of HIV to AIDS. The link between selenium and thyroid function is due to the fact that selenium is a component of the enzyme that converts the thyroid hormone from a less active form (called T4) to its active form (known as T3). Therefore, if the body does not have enough selenium, it may cause thyroid function to be impaired, leading to hypothyroidism.
Selenium’s role in heart health is related to its ability to reduce the risk of blood clots forming, which is one of the main causes of heart attacks and strokes. Selenium is also believed to increase the ratio of HDL (“good”) cholesterol to LDL (“bad”) cholesterol, another important factor in reducing the risk of cardiovascular disease. Other benefits of selenium include possible anti-inflammatory properties and protection against cataracts and macular degeneration.
Selenium: could be your most potent ally against cancer. Selenium is a trace element found naturally in foods like nuts and liver. Nearly all of the selenium in animal tissue is found in the proteins. Some of these proteins contain stoichiometric quantities of selenium and are known as selenoproteins. Other proteins contain variable amounts of selenium (which substitutes sulfur randomly in the original protein) and are known as selenium-binding proteins.
Researchers for more than 20 years animal studies have suggested that tiny amounts of selenium in the diet can reduce the risk of cancer in several organs, but much less is known about the anti-cancer benefits of selenium in humans. In recent years, laboratory experiments, clinical trials and epidemiological data have established the role of selenium in the prevention of a number of degenerative conditions including cancer, inflammatory diseases, cardiovascular disease, neurological diseases, aging, and infections. Most of these effects are related to the function of selenium in the antioxidant enzyme systems. A good source of selenium is a high-quality liquid multivitamin.
A study at the University of Arizona in Tucson in 1996 found that people who took 200 mcg of selenium a day for four and a half years reduced their risk of cancer by 32 percent and their risk of death from cancer by 50 percent. It seems, though, that someone’s genes may determine whether or not selenium supplements may reduce the risk of breast cancer. New research suggests that people with a certain genetic variation may benefit more from taking the popular nutritional supplement to reduce their risk of breast cancer.
Numerous research reports indicate that higher blood levels of selenium lowers mortality from cancer including lung, colorectal, prostate and skin cancer1. Laboratory studies indicate the potentially beneficial role of selenium in the management of mammary cancer2. Selenium is an antioxidant and appears to regenerate vitamins E and C so that they can continue to fight free radicals. Selenomethionine is its best form. You need 200 mcg a day with food. Be aware that doses of more than 400 mcg daily can be toxic.
Research also shows that a lower antioxidant status has been linked to higher incidence of cardiovascular diseases due to increased levels of LDL oxidation3,4. Selenium is one of the antioxidants that may help to inhibit LDL oxidation.
Indeed, Selenium is one of the antioxidant vitamins recently reviewed by The National Academy of Sciences (NAS)5. The new RDAs for antioxidant nutrients are: vitamin C (75 milligrams (mg) for women and 90 mg for men), vitamin E (15 mg), and selenium (55 micrograms (mcg)).
The NAS report also established tolerable upper intake levels (ULs) for vitamin C (2,000 mg), vitamin E (1,000 mg) and selenium (400 mcg). ULs for adults are set to protect the most sensitive individuals of the general population. Selenium is reported to mimic the action of insulin. Studies have shown that selenium mediates a number of insulin-like actions such as stimulating glucose uptake and regulating metabolic processes including glycolysis, gluconeogenesis, fatty acid synthesis and the pentose phosphate pathway.
Although the exact mechanism of the insulin mimicking action of selenium has as yet to be elucidated, it is reported that these actions are mediated through the activation of key proteins involved in the insulin-signal cascade6. Selenium is also reported to play a role in reducing the oxidative stress associated with diabetes7, thereby retarding the progression of the secondary complications of diabetes such as neuropathy, retinopathy and cataracts. Low selenium status has been associated with the incidence of arthritis. Studies show the beneficial role of selenium as a free radical that delays the progression of this condition.
Low levels of selenium in HIV /AIDS sufferers have been linked to higher mortality. Low plasma selenium status has also been linked with senility and cognitive decline in the elderly and with Alzheimer’s disease. Selenium supplementation was observed to reduce the severity of epileptic seizures in children. Selenium supplementation is also reported to improve confused and depressed mental states; mental fatigue and anxiety in adults.
Selenium deficiency reduces the activities of the selenium-dependent antioxidant enzymes, leading to a number of functional disorders including skeletal muscke dysfunction, cardiac dysfunction, hepatic degradation, increased capillary permeability, and pancreatic degeneration. Very low selenium status is a factor in the etiologies of a specific type of juvenile cardiomyopathy (Keshan’s Disease) and a chondrodystrophy (Kaschin-Beck Disease) that were observed in selenium-deficient regions of China.
Where to get selenium?
As selenium originates in soil, it can mostly be found in plant foods that grow in selenium-rich soil, including brazil nuts, wheat, oats and rice – depending, of course, on the selenium content of the soil in which they grow. These crops will usually convert selenium into an organic form that can be absorbed by the body. Animals that eat grains or plants grown in selenium-rich soil also have higher levels of selenium in their flesh and organs. Shellfish is another non-plant food that also contains selenium.
Most people get plenty of selenium in their daily diets, so you don’t have to worry too much that you have selenium deficiency. We only need a trace amount to stay in good health – 70mcg per day for men, and 55mcg per day for women. Selenium in the form of dietary supplements are commercially available, but beware of selenium overdose. Do not exceed the maximum level of 400mcg per day, or you could get selenium poisoning, which can lead to depression, nausea and vomiting, nervousness, loss of hair and fingernails, and even bad breath.
If you have thyroid deficiency, you may be considering selenium supplementation to help improve your thyoid levels. However, make sure that you do not exceed the recommended dosage, because too much of something that is good for you is not necessarily a good thing. Talk to a nutritionist, dietitian or pharmacist about whether you need selenium for your health, and how to add just the right amount into your daily diet.
Star newspape. Mar 18, 2012
By Datuk Dr Nor Ashikin Mokhtar
