What Does Selenium Do for Your Body?
Selenium is a trace mineral that is a critical component of selenoproteins, which play a major role in several bodily functions. These include DNA synthesis, protecting against oxidative damage and infection, and regulating thyroid hormone metabolism. A well-functioning thyroid gland is vital for controlling growth, development, and metabolism. The antioxidant properties of selenium help protect cells from damage caused by free radicals, which are unstable molecules that can contribute to chronic diseases like heart disease, Alzheimer's, and certain cancers. In addition, selenium supports immune system function and reproductive health.
Are You Getting Enough Selenium from Your Diet?
For most people in countries like the United States, a selenium deficiency is rare because the soil is typically rich in the mineral, which means the food grown in it contains sufficient amounts. However, in regions with selenium-poor soil, such as parts of Europe, Asia, and Africa, deficiency can be more common. Certain health conditions can also impair selenium absorption. These include individuals on kidney dialysis, those with HIV, or people with gastrointestinal disorders like Crohn's disease. If you are not in one of these at-risk groups and eat a balanced diet, it is highly likely that you are meeting your daily requirements through food alone.
Food Sources of Selenium
A variety of foods are good sources of selenium. The concentration can vary depending on the soil content where the food was grown. The list below highlights some of the best dietary sources:
- Brazil nuts: A single nut can provide more than the daily recommended intake.
- Seafood: Tuna, sardines, and crab are excellent sources.
- Meats: Lean meats like beef, pork, and chicken provide significant amounts.
- Eggs: A simple and reliable source of selenium.
- Grains: Breads, cereals, and rice can be good sources, especially if fortified or grown in selenium-rich soil.
- Legumes and Nuts: Lentils, beans, and sunflower seeds are also contributors.
Risks of Taking Selenium Every Day
While a little bit of selenium is essential, too much can be toxic. The tolerable upper intake level (UL) for adults is 400 micrograms (mcg) per day, a level that can be reached easily with high-dose supplements or by eating a few too many Brazil nuts. This toxicity is known as selenosis.
Symptoms of Selenosis
Early signs of chronic selenium toxicity include:
- A garlic-like odor on the breath
- A metallic taste in the mouth
- Hair loss and brittle nails
- Gastrointestinal upset like nausea or diarrhea
- Fatigue and irritability
- Skin rashes
More severe cases of selenosis can lead to severe neurological symptoms, breathing problems, kidney failure, and heart problems. The narrow range between the required amount and the toxic level is a significant reason why daily supplementation is generally not recommended for the average person.
How to Approach Selenium Intake: Food vs. Supplements
Most healthcare professionals advocate a 'food first' approach to getting vitamins and minerals. The table below compares obtaining selenium from dietary sources versus daily supplementation.
| Feature | Selenium from Food | Daily Selenium Supplements |
|---|---|---|
| Dose Control | Variable, dependent on soil quality and portion size. Requires attention to food types. | Precise, a controlled dose is delivered in each pill. |
| Risk of Toxicity | Low, unless consistently consuming extremely high-selenium foods like multiple Brazil nuts daily. | Higher, particularly with high-dose supplements, as it's easier to exceed the 400 mcg UL. |
| Absorption | Can be affected by interactions with other nutrients and digestive health, though generally well-absorbed. | Can interact with certain medications, including antacids, statins, and chemotherapy drugs. |
| Additional Nutrients | Provides a host of other vitamins, minerals, and antioxidants for overall health. | Typically provides an isolated nutrient, lacking the synergistic benefits of whole foods. |
| Necessity | Adequate for most people in North America and other regions with sufficient soil selenium. | Necessary for those with a confirmed deficiency or specific medical conditions. |
When Might Daily Selenium Supplementation Be Considered?
Daily supplementation should only be considered under the guidance of a healthcare provider. It may be appropriate for individuals with a diagnosed selenium deficiency, those with specific conditions like autoimmune thyroiditis where supplementation can be beneficial, or people on kidney dialysis who have trouble maintaining adequate levels. Your doctor can determine if supplementation is necessary and the appropriate dosage to avoid adverse effects. For further details on the nutrient, refer to the Office of Dietary Supplements at the National Institutes of Health.
Conclusion
For the vast majority of people, taking selenium every day is unnecessary and potentially risky due to the narrow therapeutic window and the risk of toxicity. A balanced diet rich in protein sources like seafood, meat, and eggs, along with some nuts and grains, provides sufficient selenium for most individuals. The 'food first' approach is the safest and most effective way to maintain adequate selenium levels. Supplements should be reserved for cases of diagnosed deficiency or specific medical conditions, always under the supervision of a healthcare professional. Listen to your body, consult an expert, and let your diet be your primary source of this essential trace mineral.
