Tag: Cancer

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Selenium and Cancer Prevention – the Evidence

The evidence for the use of selenium supplementation in cancer prevention is still inconclusive. Rataan et al suggest that the fault may lie in the design of the existing studies. At least two factors have contributed to this lack of conclusive evidence:

  • the use of different compounds in the tests of selenium and cancer
  • the different blood selenium levels of the study participants at baseline
Cancer patients
Selenium supplementation of individuals with low dietary intakes of selenium may help prevent the development of certain types of cancer.

As an example, Rataan et al cite the differences between the Nutritional Prevention of Cancer (NPC) trial and the Selenium and Vitamin E Cancer Prevention Trial (SELECT). In the NPC study, the researchers used a selenium-enriched yeast supplement. This yeast formulation contained mostly selenomethionine but also contained several other selenium species including Se-methylselenocysteine. In the SELECT study, the researchers used a 100% selenomethionine supplement. It now seems clear that the chemopreventive effect of selenium that was seen in the NPC study but not seen in the SELECT study must have come from some selenium species other than selenomethionine. The most likely chemopreventive selenium species is the Se-methylselenocysteine [Rataan 2022; Marshall 2017]. read more

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Selenium May Reduce the Risk of Heart Disease and Some Cancers

Reduced risk of heart disease and reduced risk of some cancers. Increasing the daily intake of selenium among individuals with low selenium status may reduce the risk of cardiovascular disease and some cancers. The available data seem to show that most adults in the Nordic and Baltic countries, with the exception of adults in Finland, have low selenium intakes and low selenium status [Alexander & Olsen 2023].

Jan Alexander
Prof. Jan Alexander, MD, PhD, Norwegian Institute of Public Health in Oslo, says: There are various factors that influence cardiovascular disease mortality and cancer incidence: diet, lifestyle, genetics, inter alia. The impact of these factors varies from one Nordic country to the next.

Selenium is an essential trace element. The human body cannot synthesize it. It must come from the diet and supplements. Selenium is a vital component of selenoproteins that are critical to normal health and physiological functioning. This is the fundamental message from a 2023 selenium scoping review conducted for the Nordic Nutritional Recommendations 2023 [Alexander & Olsen 2023]. read more

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ChatGPT Answers About Different Forms of Selenium Supplements

In our last article, we asked ChatGPT about the health benefits of selenium supplements in Europe. This time, we asked what is the best form of selenium supplement?

ChatGPT about selenium
We asked ChatGPT for information about the various forms of selenium supplements.

ChatGPT answered that the best form of selenium supplement depends on various factors. These factors include individual health needs, dietary habits, and preferences. Each different form of selenium supplement has its own set of advantages and considerations.

  • Selenomethionine: This form of selenium is found in foods like Brazil nuts, grains, and legumes. The body absorbs selenomethionine well.
  • Sodium selenite: This is an inorganic form of selenium. It is generally considered to have lower bioavailability compared to organic forms like selenomethionine and selenium yeast.
  • Selenium yeast: Selenium yeast is produced by fermenting the yeast Saccharomyces cerevisiae in the presence of selenium. It contains various species of selenium including selenomethionine. The yeast is inactivated in the supplements.

Editor’s note: The presence of various other species of selenium in the selenium yeast may be important for cancer prevention. By other species, we mean the selenium species other than the selenomethionine that is in the selenium yeast supplements.

  • In the Nutritional Prevention of Cancer study, researchers administered 200 mcg/day of selenium-enriched yeast for an average of 5.4 years. The study results showed a significant reduction of colorectal, lung, prostate, and total cancer incidence [Clark 1996].
  • In the SELECT study, researchers administered selenium in the form of selenomethionine, 200 mcg/day. The supplementation with selenomethionine alone and also together with vitamin E did not show any reduction of the risk of colorectal, lung, or prostate cancer after 5.5 years of follow-up [Lippman 2009].

Thus, it seems that the protective effect against cancer may have come from one or more of the other selenium species in the selenium yeast preparation, not from the selenomethionine in the preparation [Bjørnstedt 2010]. read more

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Selenium-Enriched Yeast Supplementation Studies

The rationale for taking a selenium-enriched yeast preparation: one or more of the selenium compounds in the preparation other than selenomethionine may be the selenium species that has specific effects against cancer. This is an area for further research.

Glass of beer made using brewer's yeast
Selenium-enriched yeast preparations use Saccharomyces cerevisiae, commonly known as as brewer’s yeast. The yeast is grown in a selenium-enriched medium in which the yeast absorbs the selenium. The finished preparation is pasteurized, causing the yeast cells to die. Selenium-enriched yeast preparations contain many organic selenium compounds in addition to selenomethionine.

This week, we focus on studies conducted with a selenium-enriched yeast preparation containing at least 20 different species of selenium in addition to selenomethionine [Bendahl & Gammelgaard 2004].

Randomized, double-blind, controlled clinical trials are the gold standard method for testing the safety, absorption, and efficacy of nutritional supplements and medical drugs. Below, we summarize some of the important clinical trials of nutritional interventions using selenium-enriched yeast. read more

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Selenium and Radiation Therapy for Cancer Patients

Cancer patients tend to have reduced serum selenium concentrations compared to healthy controls. Adjuvant selenium supplementation improves the protection of healthy tissue in tumor patients undergoing radiation therapy [Muecke 2018].

Cologne cathedral in Germany
15 years of experience with adjuvant selenium supplementation in radiation oncology in Germany has yielded a solid knowledge database. As a result,  some radiation oncologists measure the patient’s selenium levels during therapy and compensate in cases of selenium deficiency. Even so, it is important to remember that selenium status is  a relatively small piece in the bigger puzzle of therapeutic success in radiation oncology.

In a 2018 review of 15-years of experience with selenium supplementation in radiation oncology, Muecke et al [2018] reported on two randomized controlled trials. The researchers observed positive effects of the supplemental selenium and no adverse effects in the patients undergoing radiation therapy:

  • 81 patients with uterine cancer
  • 39 patients with head and neck tumors
Selenium Deficit in Cancer Patients

In the majority of the tumor patients (carcinomas of the uterus, head and neck, lungs, rectum or prostate) whom they examined, German researchers found a relative selenium deficit in whole blood or serum [Muecke 2018]. read more

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Selenium Supplementation and Chemotherapy in Cervical Cancer Patients

Selenium yeast supplementation administered concurrently with chemotherapy and radiation therapy effectively increased blood selenium levels in cervical cancer patients with inadequate selenium status. The selenium yeast supplementation was used as an adjuvant treatment to the standard chemotherapy and radiation therapy. It significantly decreased the hematologic toxicity of the chemoradiotherapy [Yang 2023].

Cancer and selenium
Each year, worldwide, half a million women are diagnosed with cervical cancer, and 300 000 die from the disease. In most cases, the human papilloma virus is the cause of the disease [Cohen 2019]. The trace element selenium has antiviral properties. Cell studies and mouse studies of cervical cancer have shown that different selenium species have anticancer effects in cervical cancer induced by human papilloma virus or by chemical carcinogens [Jablonska 2021].
In a randomized controlled trial, researchers randomly assigned 104 patients diagnosed with stage IIB cervical cancer receive 100 mcg selenium yeast tablets (n=50) or matching placebos twice daily (n=54) for five weeks [Yang 2023].

All patients in both groups received the standard treatment including pelvic external irradiation, concurrent five cycles of chemotherapy, and brachytherapy [Yang 2023]. read more

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Impact of Selenium Status on Biological Aging

Aging. Getting up in years. Striving to live as long as possible and to be as strong and healthy as possible. At some point, good health becomes a more important concern than wealth. Optimal selenium status is important to good health [Alehagen 2021].

Professor Jan Aaseth
Professor Jan Aaseth, MD, PhD, researcher in internal medicine, endocrinology, and toxicology and specialist in selenium research.

In a review article, Professor Urban Alehagen and Professor Jan Aaseth list the following conditions associated with biological aging [Alehagen 2021]:

  • chronic mild to moderate systemic inflammation
  • detrimental DNA alterations
  • mitochondrial dysfunction
  • oxidative stress caused by harmful free radicals
  • telomere shortening

Getting old is inevitable. Biological aging necessarily involves a weakening of the immune system and increased susceptibility to diseases and environmental stresses.

Selenium deficiency associated with aging and aging-related diseases

Selenium deficiency is associated with mitochondrial dysfunction, oxidative stress, and inflammation [Alehagen 2021].

Mitochondrial injuries are an important factor in the aging of human cells.  A by-product of the mitochondrial generation of ATP energy in the cells is the production of reactive oxygen species, some of which are useful and some of which are harmful. The leakage of these harmful free radicals from the mitochondrial respiratory chain increases with age, which results in cellular oxidative damage, whenever there are not enough antioxidants to neutralize the effects of the free radicals. read more

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Breast Cancer Recurrence and Selenoprotein P Autoimmunity

Breast cancer prognosis is especially poor in patients with low serum selenium and serum selenoprotein P concentrations. Now, researchers have discovered natural autoantibodies with antagonistic properties to selenoprotein P uptake in breast cancer patients and  in patients with thyroid disease [Demircan 2022; Sun 2022].

Autoimmunity
Autoimmunity is the production of antibodies against the tissues or substances of one’s own body, resulting in an autoimmune disease or hypersensitivity reaction. Autoantibodies to Selenoprotein P impair the transport of the essential trace element selenium in breast cancer patients and in Hashimoto’s thyroiditis patients.

Selenium is an essential trace element that has numerous biological functions in the body, most of which are carried out by selenium-containing selenoproteins. Among the more important selenoproteins are selenoprotein P, the main transporter of selenium in the blood, and glutathione peroxidase 3 (GPX3), an important antioxidant.

The human body does not synthesize selenium. Human cells are dependent upon selenium sources in the diet. Unfortunately, the selenium content in the soil and in food varies considerably from region to region in the world. For example, the plasma selenium concentrations in people living in much of Europe are generally below, often well below, 80–90 mcg/L whereas people living in North America generally have plasma selenium levels above 120 mcg/L [Alehagen 2022]. read more

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Selenium Exposure Studies

Selenium exposure in the diet and in supplements: in this review article, we summarize the key outcomes of the best selenium exposure studies.

Optimal Selenium Intake and Status

In his review of the available research literature, Professor Urban Alehagen, Linköping University, Sweden, concluded that a daily intake of 100–150 mcg of selenium per day is required.

This is the intake level that enables an optimal expression of the important selenoprotein P that transports selenium from the liver to peripheral tissues [Alehagen 2022].  For other selenoproteins to be optimized, i.e., to be fully expressed, Prof. Alehagen argues that selenium status of approximately 120 mcg/L when measured in red blood cells is necessary [Alehagen 2022]. read more

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Serum Selenium Levels Predict Breast Cancer Prognosis

Research done in southern Sweden shows that three blood biomarkers of selenium availability correlated inversely with mortality from breast cancer. The lower the three selenium biomarker levels, the higher the mortality [Demircan 2021].

Breast cancer awareness
Assessment of selenium status at the time of breast cancer diagnosis identifies patients at exceptionally high risk for a poor prognosis. They are breast cancer patients with low levels of selenium, selenoprotein P, and glutathione peroxidase in their blood.

The blood biomarkers are:

  • Total selenium
  • Selenoprotein P
  • Glutathione peroxidase 3

Breast cancer patients with blood concentrations of these three selenium biomarkers in the highest quintile had significantly better chances of survival compared with patients whose blood levels of these substances were in the lowest quintile [Demircan 2021].

Breast cancer patients with low selenium status according to these three biomarkers had the highest mortality risk with an overall survival probability of approximately 50% after 8 years. The difference in survival between the breast cancer patients in the lowest selenium quintile compared to breast cancer patients with at least one biomarker in the highest quintile was especially notable [Demircan 2021]. read more