Selenium Critical to General Health and Thyroid Function
by Mary J. Shomon
Researchers writing in the July 15, 2000 issue of the British-based
international medical journal, The Lancet , called attention to the
importance of selenium to health, citing the trace mineral's potential to
reduce the risk of thyroid problems, pregnancy and fertility problems,
heart disease, and progression of HIV to AIDS, among other important
According to the review study, diet and geographic location can impact the
amount of selenium you are getting. Selenium is an essential trace mineral
found in the soil. Typically, crops will convert selenium into organic
forms that can be absorbed nutritionally by humans. Getting sufficient
quantities of selenium may increase thyroid hormone metabolism, improve
fertility, help fight cancer, and reduce risk of cardiovascular disease
The author of the study, ("The importance of selenium to human health,"
The Lancet , Volume 356, Number 9225, 15 July 2000), Margaret Rayman, a
professor of nutritional medicine at the University of Surrey in
Guildford, England, began focusing on selenium several years ago, after
her research into the condition known as preeclampsia showed that low
selenium levels were a common denominator in all the women in the study.
Her research went on to discover that in the UK, and in Europe as well,
selenium levels were abnormally low overall. Rayman found that dietary
consumption of selenium had dropped 50% in the past two decades, a time
period during which the UK had reduced it imports of selenium rich North
American wheat in favor of selenium poor European wheat.
In addition to the relationship to early miscarriage, male infertility,
mood problems, thyroid disorders, cardiovascular disease and arthritis,
Rayman also discovered that selenium plays a key role in viral infections.
In particular, higher selenium levels can help slow down the replication
of the HIV virus. Her study actually found that "AIDS patients with low
levels of selenium were 20 times more likely to die from an AIDS-related
illness than those with healthy levels of the mineral."
In addition to selenium supplements, selenium-rich foods such as kidney,
liver, crab, other shellfish, and Brazil nuts can be eaten. North American
soil is also selenium rich, and crops grown in this soil have higher
levels of selenium. Researchers believe that most North Americans are
probably getting enough selenium, and caution that too much selenium can
be toxic. The maximum level of selenium recommended per day for adults is
400 micrograms per day. However, some studies have shown that certain
areas of the U.S., including, for example, the Eastern Coastal plain of
the U.S., have selenium-deficient soil as well, so dietary exposure to
selenium may be inconsistent.
Regarding the thyroid, selenium is a component of the enzyme that helps
convert T4 to T3 peripherally, so deficiencies of selenium may impair
thyroid function and promote hypothyroidism. According to the New England
Journal, "selenium deficiency can result in thyroid injury and decreased
extrathyroidal triiodothyronine production" (reduced peripheral T3
production.) Some experts believe that low T3 levels may be characteristic
in areas with insufficient selenium. Studies also show that excess intake
of selenium may also depress T3 levels . With some scientists suspecting
that there may be a viral component or trigger to certain autoimmune
conditions such as the common thyroid condition known as Hashimoto's
Disease, the anti-viral properties of selenium also become more
interesting, and further research into that connection as relates to
thyroid disease particularly would be illuminating.
Implications for Patients: The key issue for thyroid patients is making
sure you get enough, but not too much, selenium. Talking to a good
nutritionist or holistic physician can help you determine if selenium
might help your health and thyroid function.