Selenium
Selenium is an essential trace element that is required for health, though selenium deficiencies are rare.  It is found in relatively high concentrations in meat, seafood, cereal grains, and nuts.  It is essential in some major proteins and enzymes including glutathione, a primary antioxidant enzyme.  Overall, supplementation with a cocktail of selenium, vitamin A, and vitamin C may increase athletes’ antioxidant defenses against oxidative stress.  However, consumption of selenium alone in concentrations over and above the recommended daily intakes is not recommended based on the current data.

Serine
Serine is an amino acid that the body can synthesize from other nutrients.  It is essential for the activity of many enzymes, including those involved in the immune response.  A serine deficiency due to errors in protein metabolism can lead to problems in neurodevelopment, but deficiencies are rare.  There are not any studies to date investigating the effects of serine supplementation on sports performance.

Sibutramine
Sibutramine is a weight loss supplement that acts by two separate mechanisms: 1) decreasing appetite and 2) increasing thermogenesis, or burning extra calories to produce heat.  In combination with lifestyle changes, 10-20 mg sibutramine is an effective weight loss supplement.  However, sibutramine was banned in most developed countries in 2010 because it was thought to increase the risk of heart attack, stroke, and other cardiovascular-related events.