Selenium utilization in humans - a long-term, self-labeling experiment with stable isotopes
Article Abstract:
There are about 15 chemical elements which are important to human nutrition in trace amounts, that is, less than 20 milligrams are required by the body per day. One such element is selenium, which plays a critical role in the function of some enzymes. It is quite difficult to directly monitor the use of selenium by the body, because the element is bound up in a variety of organic chemicals. For this reason, the excretion of selenium cannot be measured by injecting an isotope of selenium and then measuring it as it leaves the body. The injected selenium is simply not in the same form as the selenium normally in the blood, and the results cannot be considered comparable. To circumvent this problem, a lengthy experiment was devised to monitor the utilization of selenium in the human body. Human subjects were given 200 micrograms per day of selenium-74, a non-radioactive but distinct isotope of selenium. After three weeks, a pint of the volunteer's blood was removed and stored frozen. Over the next 11 months, it was possible to monitor the presence of residual selenium-74 in the subject. At this time, the blood was returned to the subject from which it was taken. Better than an injection of selenium, the blood contained the selenium in all its natural, representative forms. After 11 months, there was still selenium-74 circulating in the red blood cells of the subject. This demonstrates that the selenium must be recycled, since the life-span of a red blood cell is about four months. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Clinical Nutrition
Subject: Health
ISSN: 0002-9165
Year: 1990
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Biochemical indices of selected trace minerals in men: effect of stress
Article Abstract:
Infection, inflammation and trauma are forms of stress that cause biochemical and hormonal changes in the body. These changes are referred to as an acute-phase response. During an acute-phase response, plasma levels of copper, ferritin (a protein containing iron) and ceruloplasmin (a protein containing copper) increase, while zinc and iron concentrations decrease. These biochemical changes, stimulated by physiological stress, may aid in tissue repair and immune response to infection. Physical activity has been shown to produce changes in acute-phase proteins, similar to the changes observed in response to infection. The effect of physical activity on mineral concentrations has not been determined. Therefore, the effects of five days (called "Hell Week") of intense physical activity, psychological stress and sleep deprivation on plasma mineral concentrations were determined in 66 male military trainees. The average age of the study group was 22 years. Following the five-day test period, plasma levels of zinc, iron and albumin (a blood protein) were reduced, while ferritin and ceruloplasmin levels increased. Also, white blood cell counts increased by 60 percent and hematocrit decreased by 9 percent. These findings indicate that an acute-phase response was produced in response to the five-day stress period. The biochemical and hematological (blood) changes observed immediately following the test period disappeared within the following week. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Clinical Nutrition
Subject: Health
ISSN: 0002-9165
Year: 1991
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Selenium utilization during human lactation by use of stable-isotope tracers
Article Abstract:
During lactation, women must ingest certain nutrients, such as selenium, to meet their nutritional needs as well as those of their children. Studies show that 100 to 200 nanomoles of selenium are lost in milk, and such losses may be offset by increased absorption and retention or decreased urinary excretion of selenium. Selenomethionine (SeMet) is an organic form of selenium that is better absorbed than the inorganic form called selenite. The utilization of SeMet and selenite was assessed in six lactating and six nonlactating women two to three months after childbirth and in seven women who were never pregnant. The results showed that more selenium was absorbed and retained from SeMet than selenite in all groups of women. Breast milk contained more selenium derived from SeMet than selenite. Nonlactating women and women who had never been pregnant had more urinary selenium derived from selenite than from SeMet, whereas lactating women had similar amounts of urinary selenium from both agents. Lactating women absorbed more selenium from selenite than nonlactating or nonpregnant women, although selenium from SeMet was absorbed and retained to similar extents in all women. Hence, these findings suggest that selenium losses in lactating women are mainly due to losses in breast milk. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Clinical Nutrition
Subject: Health
ISSN: 0002-9165
Year: 1990
User Contributions:
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