Tag: Pregnancy

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Selenium and Pregnancy and Thyroid Function

What Do We Know About Pregnancy and Selenium Deficiency?

First of all, during pregnancy, biomarkers of selenium status decline considerably. In some pregnancies, the blood level of selenium falls to critically low levels [Schomburg 2021].

Pregnant woman
In some studies, low selenium status in pregnancy links to a higher risk of postpartum thyroiditis, particularly in TPO-antibody positive women.

Secondly, the decline in selenium status during pregnancy reflects an increased need for selenium. During the pregnancy, both the mother and the developing fetus need selenium. The mother transfers selenium to the fetus via the placenta [Schomburg 2021].

Thirdly, low selenium status during pregnancy is associated with health risks [Schomburg 2021; Shreenath et al 2023]:

  • impaired immune system function
  • increased vulnerability to autoimmune diseases
  • increased risk of miscarriage, pre-eclampsia, fetal growth restriction, preterm labor, and gestational diabetes

Fourthly, selenium supplementation may be necessary in some cases. To date, the evidence base in support of selenium supplementation during pregnancy is somewhat limited. At this point, we need more randomized controlled trials. However, it is clear that adequate selenium status during pregnancy is important for good immune system function and for preventing the development of autoimmune conditions [Schomburg 2021]. read more

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Selenium and Mercury in the Fish We Eat

What should we know about eating fish and exposure to mercury in fish?
Fish and chips
Fish and chips. How careful should we be about eating fish? Which fish contain more harmful mercury than protective selenium? What should pregnant women know about eating fish during pregnancy?

Fact: Most fish contain mercury. Mercury is a toxic substance. Fortunately, most fish contain both selenium and mercury. On a molar basis, most edible fish contain more selenium than mercury. That makes it safe to eat most fish [Ralston 2024; Ralston 2016].

The selenium in fish binds tightly to mercury. The binding forms stable complexes that prevent mercury from damaging our cells. When there is more selenium than mercury (on a molar basis), this binding effectively neutralizes mercury’s toxicity. As a result, the mercury becomes biologically inactive and far less harmful when we eat the fish [Ralston 2023].

Even so, having just enough selenium available to neutralize the mercury exposure is not good enough. Logically, there must be a surplus of selenium. Without a surplus of selenium, there will not be enough selenium to synthesize antioxidant selenoenzymes. And, we need the antioxidant selenoenzymes to counteract the harmful free radicals in the brain. Providing more selenium, via supplementation if necessary, keeps selenoenzymes doing their antioxidant job. read more

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Selenium and Pregnancy

Maternal selenium status declines sharply during pregnancy. In selenium-poor regions of the world, the mother’s normal everyday intake of selenium is not adequate to meet the additional needs of the fetus. In such circumstances, maternal selenium status can reach critically low levels. Meanwhile, selenium supplementation has shown positive effects on the immune system, especially in pregnancy [Schomburg 2021].

Pregnant woman needs extra selenium
Biomarkers of selenium status decline in pregnancy and can reach critically low concentrations. Sufficiently high selenium status is important for an adequate immune response during pregnancy. Furthermore, selenium deficiency in pregnancy is associated with an increased risk of autoimmune disease, e.g., postpartum thyroid disorder.

In a letter to the Deutsches Ärzteblatt International, Mücke et al urge that doctors pay extra attention to the selenium status of patients in stressful situations, e.g., pregnancy, chronic or acute illness, or convalescence. They note that there is a clear risk of selenium deficiency during pregnancy. Also after giving birth, new mothers living in selenium-poor regions will likely need selenium supplementation. They will likely need extra selenium to cope with the challenging post-partum conditions [Mücke 2021; Schomburg 2021]. read more

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Selenium and Pregnancy

During pregnancy, women need an increased intake of the trace element selenium. Low selenium intake and status in the pregnant mother will be reflected directly in poor selenium status in newborns [Filipowicz 2022].

Newborn children can be low in selenium
There is a strong correlation between the mother’s selenium status during pregnancy and the selenium status of the newborn child.

Women living in regions with low selenium content in the soil and in the food most likely need a selenium supplement. A study conducted in selenium-poor central Poland has revealed that supplemental selenium in a dosage greater than 55 mcg/day can improve pregnant women’s selenium status [Filipowicz 2022].

In the Polish study, one-third of the mothers reported self-initiated additional selenium intake. For the most part, these women took a multi-vitamin and mineral supplement. The tablet added, on average, 42 mcg of selenium to their diets daily. Even so, 79% of these women had serum selenium concentrations below 70 mcg/L (selenium deficiency levels). Moreover, 22% had serum selenium concentrations below 45.9 mcg/L (severe selenium deficiency levels) [Filipowicz 2022]. read more

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Maternal Selenium Status and Offspring Risk of Autism and ADHD

A healthy pregnancy. Selenium is an essential trace element needed to support a healthy pregnancy. However, to date, studies of the mother’s selenium status and the child’s growth and development are scarce. Data from the Odense Child Cohort study in Denmark give researchers an opportunity to investigate the possible effects of the mother’s low selenium intake and low selenium status on the child’s neuro-development [Demircan 2023; Demircan 2024].

Dannebrog - Denmark's flag
Denmark is a country with selenium-poor soil and selenium-poor crops and fruits. The estimated mean daily intake of selenium in Denmark is 48 mcg/day with a 5th percentile intake of 27 mcg/day [Larsen 2004].
The pregnant women enrolled in the Odense Child Cohort study had borderline selenium deficiency status. Their serum selenium levels ranged from 57 to 75 mcg/L [Demircan 2024]. For the sake of comparison, note that Alexander & Olsen propose 110 mcg/L as an optimal selenium saturation level [Alexander & Olsen 2023]. 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 Status and the Risk of Gestational Diabetes

Lower selenium status during pregnancy means there is a greater risk of developing gestational diabetes [Hamdan 2022; Xu 2022]. Three different selenium biomarkers in early and late pregnancy show a quite strong association of selenium with 1) the risk of developing gestational diabetes mellitus and 2) the birth of large for gestational age offspring [Demircan 2022].

Storks on a nest
Low maternal selenium status is strongly associated with an increased risk of gestational diabetes and with an increased risk of large for gestational age offspring.

The Mayo Clinic defines gestational diabetes as being diagnosed with diabetes for the first time during pregnancy. Gestational diabetes is like other forms of diabetes in that it affects how well the cells use glucose. It causes high blood sugar levels that can affect the mother’s health and the baby’s health [Mayo Clinic 2023]. read more

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Selenium Supplementation and Preeclampsia Risk

Selenium supplementation of pregnant women at a high risk of preeclampsia has shown beneficial effects on 1) serum selenium levels, 2) some metabolic profiles, 3) uterine artery pulsatility index, and 4) mental health, compared to placebo. The study compared the effect in 60 pregnant women of supplementation with 200 mcg/day for 12 weeks with the effect of placebo for the same period.

Pregnant woman
Preeclampsia is a serious hypertensive condition of pregnancy. It is associated with high risk of maternal and fetal morbidity and mortality. Selenium intake and status have been linked to the occurrence of preeclampsia.

The supplementation took place for 12 weeks starting in weeks 16 to 18 of pregnancy. No side effects related to the intake of 200 mcg of selenium per day by pregnant women at high risk of preeclampsia were reported throughout the duration of the study  [Mesdaghinia 2022].

Selenium Supplementation Compared to Placebo

How did the selenium supplementation compare with the placebo supplementation in the pregnant women? read more

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Low Selenium Status and At-Risk Pregnancies

Pregnant woman
Low serum selenium status (defined as below 80 micrograms per liter) during pregnancy is associated with increased risk of miscarriage, pre-eclampsia, pre-term births, and other adverse outcomes.

A recent review article presents the evidence that low selenium status in pregnant women may be implicated in the following complications [Duntas 2020]:

  • miscarriage
  • preeclampsia
  • pre-term birth
  • retarded fetus intrauterine growth
  • post-partum hypothyroidism and auto-immune thyroiditis

To ensure an optimal pregnancy outcome, Dr. Leonidas Duntas recommends that physicians take an individualized approach and prescribe dietary and supplemental selenium intakes that are tailored to the pregnant woman’s needs.

Why is Adequate Selenium Important for Pregnant Women?

Selenium is an essential trace element. Its intake and status in the blood plasma can vary considerably according to a number of factors [Duntas 2020]:

  • differences in diet and nutrition
  • differences in soil and plant selenium content
  • ethnic differences
  • genetic differences

Without a blood selenium test, it is not possible to know whether women planning a pregnancy have sufficient circulating selenium. The Mayo Clinic reports that the normal selenium concentration in adult human blood serum in the United States is 70 to 150 micrograms per liter with a population mean value of 98 micrograms per liter. read more

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Selenium helps to avoid pregnancy complications

Adequate intakes of selenium can help to reduce the risk of some of the more serious complications of pregnancy. Studies done with an organic high-selenium yeast supplement have yielded encouraging results.

Women who have first-trimester miscarriages or recurrent miscarriages have been found to have significantly lower selenium status than women who do not miscarry.  Professor Margaret Rayman points out that blood selenium concentrations are typically lower during pregnancy, in part because there is an expansion of the volume of blood.  However, increased inflammation – implicated in miscarriages – could also be a cause of reduced circulating selenium [Rayman 2012].

For this article, I have searched the Medline database for results from randomized controlled studies involving selenium supplementation of low selenium status pregnant women.  There have been a number of interesting results.

Selenium and oxidative stress in pregnant women
Dr. Tara and a team of researchers did a simultaneous assay of pro-oxidant burden and antioxidant capacity in a total of 166 first-time-pregnant women.  In their first trimester, the women were randomly assigned to an active treatment group receiving 100 micrograms of a yeast-based selenium preparation (n=83) or placebo (n=83) per day until delivery. read more