Simple ways to improve your intake of Selenium

Elizabeth Gay reveals some more facts about this trace mineral

Recent newsletters have often mentioned the subject of Selenium and how one of the sources of this important trace mineral was lost when wheat was no longer imported into the U.K. from Canada. However, what is not generally known is that there are many other good sources of selenium which unfortunately, are seldom mentioned but which would help people in selenium deficient areas to augment their diet and thereby avoid resorting to pills and supplements.

The late Arthur Wynn, author, authority on nutrition and McCarrison Society member, wrote an excellent article for the London newsletter, in the 1990’s.  In this he says that fresh meat and fish and whole cereals are a good source of selenium in the diet with liver and kidneys having the highest selenium content of animal products.  Eskimo hunters on traditional diets have very high blood selenium levels.  Brazil nuts are probably the richest source, so rich in fact, that with a content of more than 580 microgrammes per 200 calories, they should be eaten with discretion.  Pork, lamb and beef all come high on the list, as do turkey, tinned tuna, and mushrooms.  In regions where selenium is known to be low it would be advisable to eat meat from animals raised outside the affected area.

Margaret Rayman D.Phil., writing in The Lancet in 2000,  reinforced Arthur Wynn’s observations “...despite the low availability of selenium in most European soils, bread and cereals, being commonly consumed make a substantial contribution to selenium intake in Northern Europe (about 22% in the U.K.).  Meat, poultry and fish make the biggest contribution (about 36% in the  U.K.).

Selenium, while being essential to human and animal life, is poisonous in excess and therefore, as with other important trace minerals such as zinc and manganese, it is always preferable to adapt one’s diet to include these essentials where they occur naturally in unprocessed food and therefore in the correct proportions.  However, where a supplement is advised Arthur Wynn warns, “Take no more than 125 microgrammes (µg) per day, together with vitamins A, C and E”.

The reason why selenium levels are low in some foods is often due to crops being grown on fields over igneous rocks low in selenium which cover much of Scandinavia as well as parts of Britain, notably a large area of Scotland.  In other cases, it is when land has been intensively cultivated over long periods of time thus depleting the soil of selenium and other trace minerals.

According to a report from the National Institutes of Health in the U.S.A. “Observational studies indicated that deaths from cancer, including lung, colorectal and prostate cancers are lower among people with higher blood levels or intake of selenium” and the incidence of these diseases was, “notably lower in the group given selenium supplements”.   However, a direct relationship between low selenium status and cancer has not yet been proved.  Two important long-term studies in France and the United States are now under way to investigate any selenium/cancer prevention link.

Similarly, there is insufficient data available to show whether an increase in selenium could prevent coronary heart disease.  A long-term study is currently being carried out.  The report concludes “There is evidence that selenium deficiency does not usually cause illness by itself.  Rather, it can make the body more susceptible to illnesses caused by other nutritional, biochemical or infectious stresses.”

This last observation may be particularly relevant with regard to HIV.  In her paper, Margaret Rayman noted, “selenium seems to be a crucial nutrient for HIV-infected individuals.  It is a potent inhibitor of HIV replication in vitro.”  Researchers found that selenium-deficient HIV patients were nearly twenty times more likely to die from HIV-related causes than those with adequate levels.

Whilst acknowledging the importance of selenium to human health, Margaret Rayman stressed the need to await the results of clinical trials such as those being carried out by PRECISE (Prevention of Cancer by Intervention with Selenium) and SELECT (Selenium and Vitamin E Cancer Prevention Trial), a twelve year study funded by the US National Cancer Institute, and other on-going trials.  In the meantime, she issued a word of warning, “… we must be careful not to encourage the over consumption of selenium supplements…..it must be remembered that selenium is a toxic mineral with a fairly small therapeutic window.  In some sensitive individuals, the maximum safe dietary intake may be as low as 0.600µg/day.  It would therefore seem prudent to restrict adult intake from all sources to an upper limit of 400—450µg/day as recommended by several expert panels.” Pressing for a return to the importation of Canadian wheat is no longer economically viable, nor desirable in the light of genetically modified crops in that Continent.  The Soil Association has recently produced a report based on a six year study showing that in the U.S. and Canada, G.M. crops, far from reducing the amount of weed-killer needed, as promised, they actually used more.  Large amounts of Atrazine had to be applied because of the growing ineffectiveness of Roundup.

Adding selenium to agricultural fertilisers in areas where levels are known to be low could be one solution, as is done in Finland, New Zealand and some other countries, but better still would be to make people aware that with a diet that included a wide variety of different foods, as mentioned earlier, any possible risks associated with low selenium status could, in most cases, be avoided.

References

National Institutes of Health.  Office of Dietary Supplements—1.8.2004

The Lancet Vol: 356. 2000  Margaret Rayman D.Phil.