Overview of Selenium :
Selenium is a mineral found in the soil and naturally appears in water and some 
foods. As a nutrient selenium is vital to our health and is an essential mineral 
i.e. it must be obtained through our diet. Human body needs a very little amount 
but it plays key roles in important processes like metabolism and thyroid 
function. It also has antioxidant properties.
Below are important "Health Benefits of Selenium":
1. Antioxidant Properties:
2. May help keep heart healthy:
3. Good for thyroid health:
4. Boosts immune system:
5. Helps preventing mental decline: 
6. May reduce risk certain cancers like prostate, breast, lungs and colon 
cancers:
Following are the best "Dietary Sources":
1. Fish especially tuna and sardines
2. Oyster
3. Eggs
4. Nuts
5. Mushrooms
6. Sunflower seeds
7. Chicken especially breast steaks
Excessive Intake of Selenium :
Consuming too much selenium is toxic and even may be fatal. So we should never 
exceed the tolerable amount, recommended daily amount is 55 mcg and upper 
tolerable amount is 400 mcg/day.
Usually toxicity happens after taking supplements and not due to consumption of 
selenium contained foods.
Dizziness. nausea, vomiting , facial flushing, hair loss, tremors and muscle 
sourness may the signs of selenium toxicity.