Selenium is a trace mineral required by the body in very small amounts. It is incorporated into biologically active enzymes, many of which function as antioxidants, reducing harmful free radicals. Free radicals are increased in people with poor diets and are associated with the development and progression of a number of degenerative diseases. Selenium is also involved in the recycling of other dietary antioxidants including vitamin E and alpha-lipoic acid.
The main dietary sources of selenium are plant foods including brazil nuts, wheatgerm, garlic and wholegrain products such as breads and cereals. Selenium is also found in some animal foods including fish, seafood, beef and organ meats such as liver. The selenium content of foods depends on the selenium content of the soil where the plants are grown and the animals are raised. The highest soil selenium concentrations are found in North and South America.
Diseases associated with selenium deficiency
- Reduced immune function
- Impaired thyroid function
- Depression, anxiety
- Reduced fertility
- Increased incidence of dementia
- Increased rate of progression of a number of diseases including hepatitis B and HIV
Seeking selenium
As we absorb very small amounts of this trace mineral from our diet, the level of selenium in our bodies is very sensitive to a change in our food supply. Global decline in selenium levels in the soil and the food chain over the past three decades is therefore very concerning. This decline is due to a number of factors including soil acidity, the burning of fossil fuels, acid rain and intensive farming practices.
A recent study found the selenium levels of people living in South Australia in 2002 were above those reported for many other countries, including France and New Zealand. However, these levels were significantly lower than in people from countries with a high selenium intake such as Venezuela, Japan and America. Furthermore, a dramatic decline in selenium levels was seen in South Australia from the late 1970s to the late 1980s.
Selenium at work
Cancer prevention
Recent research has highlighted selenium as a possible aid in cancer treatment and prevention. The strongest evidence is for its use in preventing certain types of cancer including prostate, colon and lung cancer. A large American study involving 1312 people, which examined the long-term effects of taking a selenium supplement, found the incidence of prostate cancer fell by 63 per cent, colon cancer by 58 per cent and lung cancer by 45 per cent. They also noted that total cancer incidence fell by 37 per cent and deaths from cancer in the treated group were 50 per cent lower than in the untreated group.
Immune boosting
Selenium supplementation improves the functions of the immune system by increasing the activation and proliferation of the body’s white blood cells and it has also been found that blood levels of selenium fall during acute illnesses. People who are particularly at risk from infection, such as athletes, the elderly and people living with HIV/AIDS, may benefit from the immune-enhancing effects of selenium.
Male fertility
It has been shown that selenium supplementation improves sperm quality in men who are sub-fertile because of sperm quality problems. There’s also evidence that selenium may improve the chance of successful conception for men who have fertility problems because of high levels of toxic heavy metals such as lead and cadmium.
How much?
The recommended dietary intake of selenium from all dietary sources is 70 micrograms (μg) for adult men and 60 micrograms for adult women per day. Selenium is needed in very small amounts by the body and large supplemental (over 200 micrograms) doses for extended periods should be avoided as it can build up in your body and become toxic.
Supplements will often contain around 26μg of selenium. It’s advisable that you get the majority of your selenium from your diet with a maximum of 100μg in the form of supplements. You should always seek the advice of a qualified naturopath if you’re concerned about specific conditions such as cancer, lowered immunity and sub-fertility as higher doses may be required to address these health problems.
Gerard Elms is a naturopath, nutritionist and herbalist with a practice in Neutral Bay. He specialises in digestive disorders and men\’s health. T: 02 9904 0734 or E: gerardelms@gmail.com
