Selenium, a trace mineral often overlooked in discussions of nutrition, plays a pivotal role in many essential bodily functions. Don’t make the mistake of forgetting about it, too!
Despite being needed in only small amounts, selenium has a huge impact on fertility, thyroid health, gut function, female reproductive hormone balance, mitochondrial health, and nervous system performance. In this article, we will explore selenium’s molecular mechanics and how it contributes to these vital areas of health. Getting enough selenium in your diet isn’t hard, but you need to know where to look; and if you are dealing with any of the above disorders, selenium supplementation might be an important step in your wellness journey.
Selenium and Fertility
Selenium plays an important role in both male and female fertility. In men, selenium is essential for sperm health, particularly sperm motility. It is a component of antioxidant enzymes like glutathione peroxidase, which protect sperm from oxidative stress, a key factor in maintaining sperm quality and function. Studies have shown that selenium deficiency can impair sperm count and motility, leading to reduced fertility potential. In my functional medicine practice, selenium is a key supplement in my treatment plans for men dealing with decreased sperm count, abnormal sperm morhpology or reduced semen volume.
For women, selenium’s role in fertility is equally important. It regulates oxidative stress (chemical damage from environmental toxins or metabolic dysfunction) to protect eggs, and supports the health of the corpus luteum, a gland that produces progesterone after ovulation. Adequate selenium levels are crucial for a healthy menstrual cycle and for preventing complications like ovarian cysts and endometriosis, as selenium deficiency can easily worsen these problems. Research has shown that selenium supplementation can improve outcomes in women undergoing in vitro fertilization (IVF), and there simply isn’t enough in a prenatal vitamin. I usually supplement my patients undergoing IVF with a form of selenium called selenomethionine because it’s best absorbed.
Selenium and Thyroid Health
Selenium is a critical nutrient for thyroid health. The thyroid gland relies on selenium to produce thyroid hormones and to protect the thyroid from oxidative damage. The two key thyroid hormones, thyroxine (T4) and triiodothyronine (T3), are produced with the help of selenium-dependent enzymes. These enzymes include deiodinases, which convert T4 into the active form, T3. Without sufficient selenium, the body cannot efficiently convert T4 into T3, which can lead to symptoms of hypothyroidism, such as fatigue, weight gain, and depression.
Furthermore, selenium acts as a potent antioxidant that helps prevent inflammation and damage to thyroid tissue caused by oxidative stress. Low selenium levels are linked to autoimmune thyroid diseases, such as Hashimoto’s thyroiditis and Graves’ disease. In fact, selenium supplementation has been shown to reduce thyroid antibody levels and improve the inflammatory markers in people with autoimmune thyroid disorders.
Selenium and Gut Health
Selenium’s influence on gut health is also significant. The gut microbiome, which plays a critical role in digestion, immune function, and nutrient absorption, relies on a delicate balance of microbial populations. Selenium supports gut health by exerting antioxidant effects that help protect the gut lining from damage caused by oxidative stress and inflammation.
Several studies have shown that selenium deficiency can lead to dysbiosis, or an imbalance in the gut microbiome, which can exacerbate conditions like leaky gut, inflammatory bowel disease (IBD), and irritable bowel syndrome (IBS). Additionally, selenium is involved in the regulation of gut-associated lymphoid tissue (GALT), a major part of the immune system that defends against infections. By supporting GALT, selenium aids in maintaining a healthy immune response in the gut, ensuring that harmful pathogens are properly neutralized.
Selenium and Female Reproductive Hormones
Female reproductive hormones, including estrogen, progesterone, and prolactin, are all influenced by selenium. As an antioxidant, selenium helps regulate oxidative stress within the ovaries and reproductive tissues, which is crucial for hormone production and overall reproductive health. Selenium plays a vital role in modulating estrogen metabolism, particularly by supporting the conversion of estrogen to its less harmful metabolites. This process is especially important in the prevention of estrogen dominance, a condition linked to several hormonal disorders, including fibroids, endometriosis, and breast cancer.
Selenium also supports progesterone production, which is vital for a healthy pregnancy. Studies have shown that low selenium levels in women are associated with menstrual irregularities, such as anovulation (lack of ovulation), which can impair fertility. By maintaining proper selenium levels, women may optimize hormone balance and reduce the risk of disorders that disrupt normal reproductive function.
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Selenium and Mitochondrial Health
Mitochondria, the energy-producing organelles in our cells, require adequate selenium for optimal function. Selenium is a key component of several antioxidant enzymes, including glutathione peroxidase, which plays a central role in protecting mitochondria from oxidative damage. Mitochondrial dysfunction is a hallmark of several chronic diseases, including neurodegenerative conditions, metabolic disorders, and cardiovascular disease. Selenium helps to reduce oxidative stress in mitochondria, which may enhance mitochondrial efficiency and energy production.
Moreover, selenium supports the synthesis of ATP (adenosine triphosphate), the primary energy currency of the cell. Studies have demonstrated that selenium supplementation can improve mitochondrial function, increase cellular energy production, and protect cells from the damage caused by free radicals. Given that mitochondrial health is foundational to overall well-being, ensuring adequate selenium intake can be a powerful strategy for maintaining energy levels and preventing age-related diseases.
Selenium and Nervous System Function
Selenium is essential for proper nervous system function due to its role in antioxidant defense and the regulation of neurotransmitter production. One of selenium’s most crucial contributions to brain health is its involvement in the enzyme glutathione peroxidase, which protects the brain from oxidative stress. Chronic oxidative stress in the brain can lead to neuronal damage, which is implicated in various neurodegenerative diseases such as Alzheimer’s and Parkinson’s.
Selenium is also involved in the synthesis of important neurotransmitters like serotonin and dopamine, both of which play vital roles in mood regulation and cognitive function. Low selenium levels have been linked to symptoms of depression, anxiety, and cognitive decline. Supplementation with selenium has shown potential in improving mood and reducing anxiety, particularly in populations with low baseline selenium levels.
Molecular Mechanics of Selenium
At the molecular level, selenium is a vital cofactor for several enzymes, most notably glutathione peroxidase (GPx) and thioredoxin reductase. These enzymes are part of the body’s primary antioxidant defense system and play a crucial role in reducing oxidative stress. By converting reactive oxygen species (ROS) into less harmful compounds, selenium protects cells from oxidative damage, which is linked to the development of chronic diseases, aging, and inflammation.
In the thyroid, selenium-dependent enzymes (deiodinases) are essential for converting the thyroid hormone T4 into its active form, T3. The conversion process is critical for the regulation of metabolism, energy production, and overall hormonal balance. Without selenium, this conversion process is inefficient, leading to symptoms of hypothyroidism.
Additionally, selenium plays a role in immune function by modulating the activity of T-cells and macrophages. It influences the production of cytokines, which are involved in inflammation and immune response. Selenium’s ability to reduce inflammation and oxidative stress is crucial for maintaining a healthy immune system and preventing autoimmune conditions, such as Hashimoto’s thyroiditis and rheumatoid arthritis.
Selenium is an essential yet often overlooked nutrient that plays a critical role in fertility, thyroid health, gut health, female reproductive hormones, mitochondrial function, and nervous system health. Its molecular action as a key cofactor for antioxidant enzymes makes it indispensable in protecting the body from oxidative stress, supporting immune function, and optimizing energy production. Given its influence on multiple physiological systems, ensuring adequate selenium intake should be a priority for anyone looking to optimize their health, particularly during periods of hormonal imbalance or stress.
For those concerned about selenium deficiency, it can be found in foods such as Brazil nuts, seafood, and eggs. Selenium is also found in some plant foods like whole grains, but it is difficult for the body to use in this form, so I typically recommend using either Brazil nuts or animal products to boost selenium intake. One of my own favorite ways to consume selenium is in the form of whole fish, such as tinned sardines (look for a BPA-free can!) In some cases, selenium supplementation may be necessary, especially for individuals with compromised thyroid function, fertility issues, or poor gut health. If you’re concerned about whether selenium deficiency is a factor in your hormones, be sure to ask your doctor for a Selenium, RBC test so you can know for sure. Test, don’t guess!
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I’m Dr. Alexandra MacKillop, a functional medicine physician, food scientist and nutrition expert.
I specialize in women’s health & hormones, addressing concerns like fertility, PCOS, endometriosis, dysmenorrhea (painful periods), PMS symptoms like bloating and mood changes and more.
If you’re looking for a new way to approach your health, I’m here to help you through it. Click to learn more.
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