The Significance of Selenium
Selenium is a trace element a
Swedish chemist, Baron Jöns Jacob Berzelius, discovered almost 200 years
ago. Today, modern scientists recognize it as "an essential mineral of
pivotal importance for human health," with anti-inflammatory, antiviral
and anti-cancer potential.1 This mineral is also a powerful antioxidant, which plays itself out
in many ways in regard to your health. You need only a little, though,
to help keep your immune system and other functions humming along in
proper order. As much as your body requires selenium, taking the proper amount is
crucial, because too much (such as 400 micrograms [mcg] daily) is
associated with an increased risk of diabetes.2 However, unless you're taking a supplement, it's not likely you'll
overdose on selenium through the foods you eat. In fact, most people
have trouble getting what they need, and as many as 1 billion people
worldwide have a selenium deficiency. Your chance of having a selenium deficiency is higher if you smoke
cigarettes, take birth control pills, drink alcohol or have a condition
that keeps you from absorbing the nutrients you need through the foods
you eat. As previously mentioned, one of the most important aspects of selenium is that it functions as a free-radical-zapping antioxidant. What does that mean, exactly? When you take the word apart, "anti" is something you're against and
the word or phrase that follows it is the "bad guy." In this case, what
you're against is oxidation because it can cause oxidative stress, which
in turn can lead to tissue and organ damage. According to News-Medical: "Oxidative stress is essentially an imbalance between the
production of free radicals and the ability of the body to counteract or
detoxify their harmful effects through neutralization by antioxidants"3 While "free radicals" may be another murky term, in short, free radicals and other assorted reactive oxygen species
(ROS) are caused by either normal, internal metabolic processes or via
outside influences such as nicotine and X-rays, or exposure to harmful
chemicals like those used to kill mosquitoes, germs in your bathroom or
weeds around your patio. One study explains: "Free radicals, reactive oxygen species (ROS) and reactive
nitrogen species are generated by our body by various endogenous
systems, exposure to different physiochemical conditions or pathological
states. A balance between free radicals and antioxidants is necessary
for proper physiological function. If free radicals overwhelm the body's ability to regulate them, a
condition known as oxidative stress ensues. Free radicals thus
adversely alter lipids, proteins and DNA and trigger a number of human
diseases. Hence application of external source of antioxidants can
assist in coping (with) oxidative stress."4 It may be helpful to remember that free radicals can cause cell damage, and antioxidants fight free radicals. Your thyroid contains more selenium per gram of tissue than any other organ. One study explains: "In 1957, studies investigating the requirements of nutrients in
rodent diets revealed selenium (along with vitamin E) to be essential
for prevention of liver necrosis. This led to the realization that
selenium deficiency was responsible for a number of disorders observed
previously … (Selenium is) a contributing factor to Keshan disease
in humans. Although toxicity at higher levels is still a serious
problem, the importance of selenium as an essential micronutrient is now
recognized."5 Another study states that the value of selenium supplementation for
people with autoimmune thyroid problems is becoming more understood and
deficiency even appears to have an impact on the development of thyroid
problems, possibly due to selenium's ability to regulate the production
of ROS and their metabolites. In patients with Hashimoto's disease, selenium supplementation "decreases anti-thyroid antibody levels and improves the ultrasound structure of the thyroid gland."6 Further, studies for pregnant women regarding selenium say that supplementation significantly lowers the risk of postpartum thyroiditis.7 According to one meta-analysis: "Selenium may play a beneficial role in multi-factorial illnesses
with genetic and environmental linkages … Tissues particularly
sensitive to changes in selenium supply include red blood cells, kidney
and muscle. The meta-analysis identified that for animal species
selenium-enriched foods were more effective than selenomethionine at
increasing (glutathione peroxidase) activity."8 Immune Function One of the most important functions of selenium is its ability to
help your body fight disease. It raises your white blood cell count so
you're more able to resist infections. An example is a study showing that selenium may help prevent a skin
infection prevalent in people with lymphedema (swelling of the tissues
in your arms and/or legs, usually as a result of chemotherapy or
injury), and mycoplasma pneumonia, aka "walking" pneumonia.9 Cancer In 2012, researchers reported that in areas of the world where
selenium levels are naturally low, supplementing with selenium may be cancer protective.10 Study author and professor John Hesketh of Newcastle University, U.K., explained: "The difficulty with selenium is that it's a very narrow window
between levels that are sub-optimal and those that would be considered
toxic. What our study shows is a possible link between higher levels of
selenium and a decreased risk of colorectal cancer and suggests that
increasing selenium intake may reduce the risk of this disease."11 Heart Benefits While it should be noted that some researchers say taking selenium
supplements doesn't appear to influence heart disease one way or the
other or protect against heart attack, the University of Maryland Medical Center reported: "Scientists know that low levels of selenium can contribute to
heart failure, and being deficient in selenium seems to make
atherosclerosis worse. Atherosclerosis, or hardening of the arteries,
happens when plaque builds up in arteries, which can lead to heart
attack and stroke."12 Another study found that patients who took selenium supplements on a
regular basis are "far less likely" to have another heart attack.13 Asthma Asthma sufferers tend to have higher incidences of low selenium
levels in their blood. Scientists found that diets containing high
amounts of antioxidants are associated with lowered asthma prevalence in
epidemiologic studies, as a report on accumulated data revealed: "Accumulated data indicate that asthma is associated with reduced
circulatory selenium (Se) … In the Se-supplemented group there were
significant increases in serum Se … Further, there was a significant clinical improvement in the Se-supplemented group, as compared with the placebo group."14 Among 24 subjects with asthma,
those who took supplements for 14 weeks had fewer symptoms than those
taking a placebo, one study found. However, scientists agree that more
studies are needed.15 Male infertility Proteins found in sperm and involved in their formation are impacted by selenium and other antioxidants. An interesting dichotomy, however, is that while studies show male infertility
may be improved by the selenium in a man's system, levels that are too
high can inhibit the sperm's ability to swim, according to the
University of Maryland Medical Center.16 Another study concluded: "Selenium-enriched probiotics or inorganic selenium
supplementation gave better results than probiotics supplementation and
may be used to improve animal and human male fertility compromised by
hyperlipidemia or obesity."17 HIV/AIDS Most of the African continent is selenium deficient. Simultaneously,
AIDS is the most common cause of death. News-Medical, examining diseases
impacted by selenium, reported: "Taken as a whole, the geographical evidence, therefore, strongly suggests that selenium is protective against HIV infection. Such a relationship is not limited to this virus. A frequently
fatal illness of the heart, known as Keshan disease, is widespread in
the population of the low selenium belt that crosses China from
northeast to southwest. Keshan disease occurs only in individuals who
are both selenium deficient and infected by the coxsackievirus"18 While the highest death rates from AIDS
affect several of the southwestern-most portions of the continent, such
as Botswana, Uganda and Kenya, "the prevalence rate for HIV infection
still hovers at an unusually low 0.5 percent among women attending
antenatal clinics" in Dakar, the capital city of Senegal. The difference, scientists say, is that Senegal is located on the far
western coast of Africa, where the soil is enriched with trace elements
of selenium, contrasting the eastern portion, where the soil is devoid
of the selenium that might help make a difference in this regard. A similar situation is taking place in Finland where, to combat heart
disease, legislation was passed in 1984 ordering sodium selenite to be
added to all fertilizers throughout the country. Perhaps as a result,
the country's HIV rates are half that of other Scandinavian countries. The best selenium sources from food include salmon (although only
wild-caught Alaskan salmon is recommended due to widespread pollution in
other fish), free-range organic turkey, lamb and grass-fed organic
beef. You can also find high amounts of selenium in Brazil nuts, sunflower seeds, onions and garlic and certain mushrooms.19 SFGate says: "Mushrooms are one of the top vegetable sources for selenium. One
cup of cooked shiitakes or white button mushrooms provides 19
micrograms of selenium, or 35 percent of the RDA. A more typical serving
of ¼ cup provides less than 10 percent of the daily value. A cup of cooked lima or pinto beans averages 9 to 11 micrograms
of the mineral, or about 15 to 20 percent of the RDA. Frozen cooked
spinach, which is packed more tightly per cup than fresh cooked,
provides 10 micrograms of selenium, or 18 percent of the RDA." It's not just how much selenium is in your food, though, that
determines how much you're getting. It's also about how much selenium is
in the soil your food is grown in. Related factors include how much
selenium was in the grass eaten by the cattle producing your grass-fed beef. (Grass-fed beef, by the way, contains a healthy ratio between omega-6
and omega-3 fats. Naturally, you also want it to be free of hormones
and antibiotics.)Free Radicals: The 'Bad Guys' You Don't Want Lurking in Your Body
Thyroid Function and the Role of Selenium
Selenium Strengths: Proper Amounts Cut Your Risk of Serious Disease
Selenium From Food: Seafood, Mushrooms and Meat
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