Selenium and good health. How much do we need? How do we get it? Generally speaking, our family and friends do not know just how important selenium is to good health. Our bodies cannot synthesize selenium. We are dependent upon food for an adequate daily intake of this essential trace element.
Mortality and morbidity. As we get older, we start to think about ways to reduce the risk of an early death. We want to reduce the risk of living out our lives in ill health.
We think about diet, exercise, 10,000 steps a day, hobbies, social contact. But, do we think about our selenium intake and status? Now, some large survey studies conducted in the US have shown that higher selenium status is significantly associated with lower mortality.
Each year, the National Health and Nutrition Examination Survey (NHANES) in the United States conducts surveys that focus on different population groups or health topics. This week, we present data from studies of selenium status and mortality.
Qiu et al examined the data from 3199 adults with type 2 diabetes. Their analysis showed that higher serum selenium concentrations are associated with lower all-cause mortality and lower heart disease mortality among individuals with type 2 diabetes [Qiu 2022].
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 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.
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.
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].
How does ChatGPT answer the question: what are the health benefits of selenium supplementation in Europe? Earlier this month, we posed that question to the free version of ChatGPT. We focused on Europe because the selenium intakes in the United States are generally much higher than the selenium intakes in many parts of Europe [Alehagen 2022].
First, ChatGPT explained that selenium is an essential trace element. It plays an important role in physiological processes in the body. It is a necessary component in selenoproteins. These selenoproteins have antioxidant properties. They help regulate immune system function, thyroid function, and DNA synthesis.
Next, ChatGPT reminded that excessive intake of selenium can lead to toxicity. Selenium supplementation should be undertaken under the guidance of a healthcare professional. Note that the Nordic Nutrition Recommendations 2023 and the European Food Safety Authority both set the tolerable upper intake level at 255 mcg/day [Blomhoff 2023; EFSA 2023].
Selenium is an essential micronutrient. Humans cannot synthesize it. Therefore, we must get it from our diets. The selenium content of our diets depends on the richness or poorness of the selenium in the soil and the food. In fact, there are surprisingly large differences in selenium content in various regions of the world [Zhang 2020a].
Selenium through its incorporation into 25 known selenoproteins is necessary for a range of biological functions. Zhang et al [2020a] list the following biological functions of selenium and selenium-derived selenoproteins:
Selenium and selenium-derived selenoproteins such as the glutathione peroxidases (GPXs), the thioredoxin reductases (TXNRDs), and the endoplasmic-reticulum-associated selenoproteins influence viral pathogenicity. Among other things, these antioxidant selenoenzymes reduce the extent of oxidative stress generated by viral pathogens. Failure to counteract oxidative stress can result in mutations in the viral genome from benign to highly virulent strains [Zhang 2020a].
Maintaining adequate selenium status is an acknowledged anti-aging strategy. We need selenium to live longer and to be healthier as we age. Adequate intakes of selenium and adequate bio-synthesis of selenoproteins contribute to healthy aging and to reduced vulnerability to various disorders. Selenium and selenoproteins are important for the following biological activity [Bjorklund 2022]:
One characteristic of aging is oxidative stress.
Oxidative stress is defined as an imbalance between the damage caused by harmful free radicals and the protection offered by antioxidants. Inadequate selenium status can reduce the longevity and the health of senior citizens by accelerating the aging process and/or increasing vulnerability to immune system dysfunction, cardiovascular disease, and cancer [Bjorklund 2022].
Blood sugar levels. Insulin sensitivity. Risk of diabetes. What, if anything, is the likely effect of selenium supplementation on glycemic control?
Glycemic control is the maintenance of blood sugar levels within an acceptable range to prevent the adverse effects of low blood sugar and high blood sugar.
The best measure of glycemic control is the HbA1c test. This blood test HbA1C gauges the average glucose level in the blood over a period of approximately three months. It is considered a good predictor of diabetic complications.
The US Center for Disease Control and Prevention suggests that logical times for testing blood sugar levels are as follows [CDC 2022]:
The CDC suggests the following desirable blood sugar levels [CDC 2022]:
The thyroid gland is the organ in the body that contains the most selenium per gram of tissue [Wang 2023].
In a 2023 review article, Wang et al summarize the reasons why adequate selenium intake and status are necessary for good thyroid health.
Humans cannot synthesize selenium: the daily intake of selenium depends on the contents of the individual’s diet.
Wang et al [2023] report the following outcomes from clinical trials of selenium supplementation. They advise that we need more clinical evidence for the efficacy of selenium treatment of thyroid disorders.
Wang et al [2023] reviewed the data from 11 clinical trials. Nine clinical trials showed that selenium supplementation results in faster achievement of normal thyroid function in patients with hyperthyroidism. Two clinical trials did not show the beneficial effect of selenium supplementation. The difference in outcomes may be related to differences in the form of the selenium supplementation, the dose, the duration of supplementation, and the nutritional status of the study participants.
Low plasma selenoprotein P levels are associated with a higher risk of heart failure in a Swedish population [Jujic 2023].
Plasma and serum selenoprotein P concentrations are useful biomarkers of selenium status in individuals with relatively low selenium intakes because selenoprotein P responds to different intake forms of selenium [Hurst 2010].
Selenium deficiency – defined as serum selenium concentrations below 70 mcg/L – has been associated with more severe symptoms of heart failure, poorer exercise capacity, and poorer quality of life. Sub-optimal serum selenium concentrations of 70–100 mcg/L have similar adverse associations, suggesting that values less than 100 mcg/L, might be considered abnormal [Bomer 2020].
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.
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.
