What is selenium?

Selenium is one of the trace minerals – the minerals our body needs in the smallest amounts. The best food sources of selenium sources are Brazil nuts and wheat germ. Other sources are whole grains (barley, wheat, rye, buckwheat, oats and brown rice), fish, seafood and lean meats, sunflower seeds and other nuts such as pecans and almonds. Selenium levels in the soil can however be very low in some areas, greatly reducing the amount of selenium that gets into our foods.

What does selenium do in the body?

The main function of selenium in our body is as an antioxidant, both on its own and as part of the enzyme ‘glutathione peroxidase’, helping to prevent free radical damage to our cells. Selenium works in synergy with vitamin E in this function.

Other functions include:

  • The production of the thyroid hormone T3 (triiodothyronine). Thyroid hormones are necessary for normal metabolism, which in turn governs many other processes in the body such as digestion, heart function and the work of the other endocrine (hormone-producing) glands.
  • Male fertility: selenium is required for testosterone synthesis and for sperm production. • Protecting against heavy metal toxicity, by binding to and/or impairing the absorption of heavy metals such as cadmium, lead, mercury and aluminium.
  • Supporting immunity: it is necessary for normal development of white blood cells.
  • Liver detoxification: as well as being part of glutathione peroxidase, selenium can also enhance the activity of glutathione, a compound used by the liver to eliminate many different types of toxins.
  • Eye health: the eyes carry a higher concentration of antioxidants than other tissues, as they are more vulnerable to free radical damage.

These antioxidants include glutathione peroxidase (which contains selenium) and selenium itself.

How can I take selenium supplements?

In supplement form, selenium is usually found in 100µg or 200µg dosages, as tablets or capsules. It can also be found as a liquid. Different types of selenium in supplements include sodium selenite, selenomethionine and yeast-bound selenium. Yeast-bound selenium is in the organically-bound form as found in many foods, so may be particularly well absorbed. Selenomethionine (selenium bound to the amino acid methionine) is a very popular form and is also thought to be very well absorbed, well retained in the body and well transported into the body’s tissues. It is also a good option for those who prefer to avoid yeast. Sodium selenite is an ‘inorganic’ form and may not be as absorbable as these other forms. Selenium can be taken on its own, but is often found in combination supplements with other antioxidant vitamins and minerals, particularly vitamins A, C and E and zinc.

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