Selenium has been promoted from being a mineral once regarded as toxic, to one that is listed as essential, albeit in minute quantities. Now hailed as a major anti-ageing mineral, it works with vitamin E to neutralize the dangerous substances known as free radicals, and to eliminate toxic substances, such as cadmium, lead and mercury. Selenium also protects from infection, promotes energy, alleviates menopausal symptoms in women and aids the production if healthy sperm in men. It helps to protect against certain chronic diseases, such as arthritis and multiple sclerosis.
Availability in Food
The selenium that occurs naturally in the soil varies greatly in different parts of the world. Where its occurrence is low, selenium is sometimes included in animal feed. As a result, the amount in our food can vary. Brazil nuts are a particularly rich source, and selenium is found in whole grains and shellfish. Levels of selenium in plants are generally low.
What if your intake is too low?
Selenium deficiency can cause fatigue, increased susceptibility to infection, premature ageing, and loss of fertility, especially in men, and may increase a risk of cancer.
When extra may be needed
- If you live in an area where the soil is deficient in selenium
- If you are a man: like zinc, selenium is lost in seminal fluid
(Pregnant and breast feeding women should consult a doctor, midwife, or qualified nutritionist before taking any mineral or vitamin supplement.)
Can too much be toxic?
Selenium is very toxic. Too much selenium can cause hair loss, tooth decay and changes in the nails, including brittleness, pallor, white spots, and even nail loss. The appetite may be poor, with a sour taste in the mouth, and the digestion can become disturbed. Numbness and loss of sensation can occur in the hands and feet. The skin may develop a reddish pigmentation, the breath may smell of a garlic-like odour.
Shampoos containing selenium are used for dandruff and it can be absorbed through the skin in minute quantities. However, it is used here in the form of selenium sulphide, which is less toxic than sodium selenite. Selenium is also used in a number of industrial processes, and can be absorbed by workers in these industries.
Selenium is probably best taken as part of a well balanced mineral and vitamin programme. The toxicity of selenium appears to vary, depending on the form in which it is taken.