Selenium, an essential trace mineral, is garnering attention for its potential role in weight management and overall well-being. While only needed in small amounts, selenium plays a key role in various bodily functions, including metabolism, thyroid function, cognitive support, antioxidant protection, immune system support, and reproductive health. This article delves into the multifaceted benefits of selenium, particularly its connection to weight loss, and provides guidance on incorporating it safely into your diet.
What is Selenium?
Selenium is a mineral naturally found in soil, water, and certain foods. It is essential for supporting healthy bodily functions, including metabolism, immune system function, and thyroid hormone metabolism. Selenium acts as a constituent of 25 selenoproteins, including glutathione peroxidases, thioredoxin reductases, and selenoprotein P.
The Multifaceted Roles of Selenium
Selenium is essential for many processes, including:
- Thyroid hormone metabolism: Selenium plays a vital role in the production of hormones secreted by the thyroid gland.
- DNA synthesis: Selenium is involved in the creation of DNA, the genetic material in cells.
- Reproductive functions: Selenium is important for a healthy reproductive system in both men and women.
- Infection prevention: Selenium helps to boost the immune system and fight off infections.
Decoding Selenium's Potential Benefits
Selenium offers a range of potential health benefits:
Antioxidant Effects
Selenium exhibits antioxidant properties by controlling free radicals, thus reducing oxidative stress and the risk of chronic diseases. It increases glutathione peroxidase, a powerful antioxidant in the body.
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Anti-Aging Properties
Selenium acts as an antioxidant, supporting glutathione peroxidase, reducing oxidative stress, protecting cells from damage, and regulating thyroid and immune function for overall anti-aging benefits.
Cancer Risk Reduction
Selenium may reduce the risk of lung, colon, and prostate cancers and the side effects of radiation therapy, though more research is needed.
Heart Disease Protection
Low selenium levels are linked to an increased risk of heart disease. Selenium may reduce inflammation, a major risk factor for heart disease.
Mental Benefits
Reduced selenium levels can be observed in people with Alzheimer's disease, and selenium may reduce memory loss. Selenium's antioxidant role is important for reducing levels of oxidative stress, supporting sharper cognitive function.
Thyroid Health
Thyroid tissue contains more selenium than any other organ in the human body, playing an important role in hormone production. Selenium can benefit people with Hashimoto's disease.
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Immunity Boost
Increased blood selenium levels are thought to be associated with an increased immune response. Selenium supplements may help boost the immune system in people with influenza, tuberculosis, and hepatitis C.
Asthma Symptom Reduction
Asthma is a chronic disease affecting the airways. Selenium may help reduce asthma symptoms.
Selenium and Weight Loss: Unpacking the Connection
The thyroid is the master gland that controls your metabolism, and if your thyroid isn’t functioning properly, losing weight is going to be a huge challenge. The thyroid requires sufficient levels of thyroid hormones to run optimally. When it comes to selenium and weight loss, most of the research revolves around the role of selenium in supporting thyroid function. Of all organs in the human body, the thyroid contains the highest selenium content per gram of tissue due to the expression of specific selenoproteins, of which some play a role in thyroid hormone metabolism while others play an antioxidant defense role.
Selenium's Impact on Thyroid Function
Selenium is a beneficial mineral that plays a key role in antioxidant defense and thyroid function. Selenium is needed for various functions critical to overall health, but especially for the thyroid. Since the thyroid gland is a key player in the body’s metabolic processes, any impact on its function could potentially affect weight regulation.
The thyroid contains high levels of selenium, which is used to make and metabolize thyroid hormones. These hormones regulate many metabolic functions in your body, including how many calories you burn.
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Selenium deficiency is linked with a higher risk of thyroid disease. Studies have shown that taking selenium supplements improves thyroid function in people with mild hypothyroid disease and autoimmune thyroid disease.
Inflammation and Weight
Chronic inflammation is associated with obesity, and selenium is known for its anti-inflammatory properties.
Research Findings on Selenium and Weight Loss
A recent study published in Nutrients considered the role of selenium, an essential trace element, in weight management. Researchers examined the relationship between dietary selenium intake and obesity in 3214 subjects. The results showed a dose-dependent relationship between higher dietary selenium intake and lower body mass index, waist circumference, and trunk, android, gynoid, and total body fat percentages. This relationship was independent of age, total dietary calorie intake, physical activity, smoking, alcohol, medication use, and menopausal status. The study authors estimated that dietary selenium intake may account for 9% to 27% of the variation in subjects’ body fat percentages.
One study of 11 men found that raising selenium intake increased weight gain. Another study of 24 participants found that consuming selenium-enriched chicken had no impact on weight loss.
In a small 12-week study in 37 adults with overweight, those who took a daily 240-mcg selenium supplement combined with a calorie-restricted diet lost more weight than a group who tried only the calorie restriction. Those who took the daily supplement also lost more fat and had lower levels of leptin, which is a hormone that helps regulate fat storage.
Selenium and Insulin
Selenium can influence insulin signaling and secretion through its antioxidant effects, and it’s even been said to have an insulin mimetic effect-meaning that it may function similarly to insulin and promote the entry of glucose into tissues, thereby lowering blood glucose levels.
According to a recent research review, several studies have found a U-shaped relationship between selenium levels in the body and Type 2 diabetes, metabolic syndrome, and insulin resistance-meaning both low and high levels were associated with increased risk. But association doesn’t equal causation, and the review authors note that supplementing with selenium “doesn’t appear to be a major causal factor for developing insulin resistance or Type 2 diabetes in humans.” In fact, the authors point out high blood glucose can actually trigger selenoprotein synthesis in the body-so elevated selenium levels found in diabetes patients could more likely be a result, rather than a cause, of metabolic problems.
Dietary Sources of Selenium
Selenium is a mineral that occurs naturally in soil and water. It’s transferred to plants and then throughout the food system. As such, it’s available in a wide variety of whole foods. The amount of selenium in a food largely depends on the soil conditions where that food was grown.
Good food sources of selenium include:
- Brazil nuts: Brazil nuts are the most powerful source of selenium available.
- Seafood: Most seafood contains high levels of selenium.
- Lean meat: Meat is an excellent source of many essential nutrients, including selenium.
- Pasta: Pasta is an easy way to include selenium in most diets.
- Rice: Because most rice is gluten-free, it can be a good option for people with wheat allergies or celiac disease.
- Eggs: One large egg can meet about 28% of your daily selenium requirement.
- Oatmeal: Whether you have a bowl for breakfast, use it to thicken smoothies, or substitute it for flour in baked goods, oatmeal is an excellent selenium source.
- Baked beans: Baked beans - and some other vegetarian products - contain about 12 micrograms of selenium per cup.
Other sources of selenium include cottage cheese, fortified cereals, lentils, and whole wheat bread.
Selenium Supplementation: Dosage and Safety
The Recommended Dietary Allowance (RDA) - which is the average daily amount of a nutrient that meets most people’s daily needs - for selenium is 55 mcg per day. Some studies suggest this RDA could be suboptimal and recommend closer to 200 mcg per day from food or a combo of food and supplements.
The safe upper limit for selenium is 400 micrograms a day in adults. Anything above that is considered an overdose.
Symptoms that you’re getting too much selenium include hair and nail loss, nail brittleness, a metallic taste in your mouth, and a garlic odor on your breath. It can also cause nausea, vomiting, and diarrhea.
If you frequently take a high dose selenium supplement on top of a selenium-rich diet, you might risk toxicity. In severe cases, this can cause kidney or heart failure.
Before taking a selenium supplement, you can first try to optimize your diet to include more of the nutrient. If opting for a stand-alone selenium supplement, make sure to check that the nutrient isn’t added to any other supplements you’re taking. According to older and newer research, selenium supplements are considered safe to take in regular doses, usually around 100-200 mcg per day.
If you choose to take a supplement, consider one that contains selenomethionine, which is more efficiently absorbed than other forms of selenium, like sodium selenite. Opting for a lower dose selenium supplement (50-100 mcg) can help you better control your intake.
Risks of Selenium Overdose
Our bodies need selenium to work well, but there are risks to adding more to your diet, including side effects. Taken at normal doses, selenium doesn't usually have side effects. But over the long term, routinely getting unsafe levels could lead to selenium toxicity, a condition linked to stomach and nervous system issues, tremors, dizziness, breathing issues, kidney failure, and heart problems. At high enough levels, selenium toxicity could even be fatal.
People with an autoimmune disease or an underactive thyroid (hypothyroidism), as well as those taking birth control pills, immunosuppressants, medicines that slow blood clotting, niacin, barbiturates, or warfarin, should talk to their doctor before taking a selenium supplement.
Deficiency
On its own, selenium deficiency rarely causes illness. However, in certain populations, selenium deficiency may trigger the development of conditions such as Keshan disease and Kashin-Beck disease.
Symptoms of selenium deficiency include headache, nausea, confusion, fatigue, and seizure.
Having a selenium deficiency could lead to infertility in men and those assigned male at birth, Keshan disease (a type of heart disease), and Kashin-Beck disease (a type of arthritis).
People who are fed through an IV are also at risk for selenium deficiency. Some health conditions, such as HIV or Crohn's disease, put you at a higher risk for low selenium levels.