Selenium is essential for the human body and is one of the most important trace elements. Selenium makes an indelible contribution to human health. Therefore, to ensure good health, foods high in selenium should be consumed more often. Selenium has many functions, which can be summarized into approximately ten:

1. Selenium can enhance the body's immune function.

2. Selenium can prevent and fight cancer.

3. Selenium can prevent and treat cardiovascular and cerebrovascular diseases.

4. Selenium can protect the liver.

5. Selenium has antioxidant properties and can delay aging.

6. Selenium can participate in the treatment of diabetes.

7. Selenium can protect and repair cells.

8. Selenium can protect the eyes.

9. Selenium can enhance the oxygen-carrying capacity of red blood cells.

10. Selenium can detoxify, prevent poisoning, and resist pollution.

Selenium has numerous benefits, impacting many aspects of human health, and is particularly relevant to men's health. For example, selenium can inhibit the growth-promoting effect of cadmium on prostate epithelium, thus alleviating the condition. Some people, lacking a comprehensive understanding of selenium, believe that its significant effects necessitate frequent supplementation. In fact, selenium should not be supplemented indiscriminately.

Like other minerals, selenium has a dual nature: moderate amounts are beneficial, while excessive amounts are harmful. While selenium supplementation is necessary, it should not be done blindly, as this can cause side effects. Some people believe they are selenium deficient and therefore blindly supplement with selenium, consuming high-selenium foods as nutritional supplements long-term to maintain a high selenium level in the body.

In fact, blindly supplementing with selenium is not advisable. Long-term exposure to high selenium levels can lead to symptoms such as dulled pain sensation in the skin, numbness in the limbs, dizziness, loss of appetite, hair loss, thickened nails, rashes, itchy skin, pale complexion, gastrointestinal dysfunction, and indigestion.

Excessive selenium supplementation can lead to selenium poisoning, which can be divided into two types:

Acute selenium poisoning

Acute selenium poisoning usually occurs after ingesting large amounts of selenium. A daily selenium intake of 400–800 mg/kg body weight can lead to acute poisoning. The main symptoms include abnormal movement and postural abnormalities, difficulty breathing, abdominal distension, high fever, rapid pulse, collapse, and death due to respiratory failure. Fatal poisoning often precedes death by direct myocardial depression and persistent hypotension caused by peripheral vasodilation. Characteristic symptoms include garlic or sour breath, nausea, vomiting, abdominal pain, restlessness, excessive salivation, muscle spasms, hair and nail loss, skin rash, peripheral neuropathy, and mottled teeth. With treatment, symptoms of acute selenium poisoning can gradually improve within 2–3 days.

Chronic selenium poisoning

Chronic selenium poisoning often results from daily intake of 2400–3000 micrograms of selenium from food for several months before symptoms appear. In addition to the symptoms of acute selenium poisoning, chronic selenium poisoning can also manifest as hepatomegaly, abnormal liver function, autonomic nervous system dysfunction, and elevated urinary selenium levels. Long-term high selenium levels can cause stunted growth and weight gain in children, rough and brittle hair, and even neurological symptoms and intellectual impairment. The main characteristics of chronic selenium poisoning are hair loss and changes in nail shape.

Therefore, even though selenium has powerful effects, we should not supplement it indiscriminately. If you are deficient in selenium, remember to follow your doctor's advice, and supplement it in appropriate amounts and at appropriate times to ensure your health and safety.