Natural Selenium-Yeast for Better Bio-Availability by Prof Margaret Rayman BSc, Dphil (Oxon), RPHNutr

The UK intake of this trace mineral has fallen by 50% in the last 50 years and levels are now low enough to be a potentially significant cause of ill health. Should you be getting more? Which type should you choose?
The trace mineral selenium is a crucial nutrient for human health.It is a component of a number of proteins and enzymes required for important biological functions such as antioxidant defence (protecting your cells from free radical damage), reduction of inflammation, thyroid hormone production, DNA synthesis, fertility and reproduction. Adequate dietary intakes of selenium are therefore essential.

Selenium enters the food chain through plants and its concentration in foods is determined by a number of geological and geographical factors. The intake of selenium in most parts of Europe is considerably lower than in many other parts of the world, as our soil is less rich in selenium than other countries. In the UK, for example, it has declined significantly in recent years due to the reduced import of selenium-rich wheat from North America for bread-making.

The recommended daily intake of selenium for adults is not now achieved in the majority of European countries, including the UK. The RNI (Reference Nutrient Intake) in the UK is 75mcg/day for males and 60mcg/day for females, whereas the average is around half what it should be, at only 29-39mcg per day. Some experts consider that a daily dose of up to 200mcg may be needed to produce anti-cancer effects.

A number of supplementation studies have indicated that selenium in yeast form is more bioavailable than inorganic selenium and that increased levels of selenium in the body persist for a longer period after selenium-yeast supplements have been taken. In addition, the bioavailability of selenium from selenium-yeast has been shown to resemble that of natural wheat-selenium rather than the inorganic type in its effect on levels in the body.

Cereals and forage crops convert selenium mainly into a substance called selenomethionine. In the same manner, bakers yeast assimilates a large amount of selenium, mainly as selenomethionine incorporated into yeast proteins. As a result of fermentation, selenium becomes organically bound to yeast. In good quality selenium-yeast, the amount bound should be greater than 90% for good bioavailability.

A number of studies have shown positive benefits of selenium-yeast. It helps the proper functioning of the immune system, appears to be a key nutrient for sperm motility and may reduce the risk of cancer, miscarriage and pre-eclampsia. In particular, it is a safe, bioavailable form of selenium that is absorbed and used by the body in the same way as natural selenium from food.

Professor Margaret Rayman (BSc, Dphil (Oxon), RPHNutr) has a doctorate in Inorganic Biochemistry and is Professor of Nutritional Medicine at the University of Surrey where she directs the highly respected MSc Programme in Nutritional Medicine.