Which trace element is recognized as an essential micronutrient?

Selenium is recognized as an essential micronutrient because it plays a crucial role in various biological processes, particularly as a component of several important enzymes known as selenoproteins. These enzymes are involved in antioxidant defense, thyroid hormone metabolism, DNA synthesis, and immune function. Selenium helps protect cells from oxidative stress and may play a role in reducing inflammation and the risk of certain chronic diseases.

In terms of dietary sources, selenium can be found in foods such as Brazil nuts, seafood, meat, and grains. It is important to maintain adequate selenium levels in the body, as both deficiency and excess can lead to health issues.

In contrast, thallium, aluminum, and mercury are not considered essential micronutrients. Thallium is toxic to humans, aluminum's biological role is not well understood, and mercury is known to have harmful effects on health. Thus, selenium stands out as the only trace element among the choices provided that is recognized for its essential role in human health.