A hero of the sports nutrition industry, Valine or L-Valine is taken up by muscle cells and immune system cells. Valine or L-Valine is used mainly an energy source for cells. It is claimed that Valine or L-Valine and other amino acids will increase endurance, prevent fatigue, improve mental functioning, boost energy levels, and strengthen the immune system. Studies on athletes have shown that Valine or L-Valine and other essential amino acids have improved endurance and reduced the time it takes to complete a course (for example, a marathon).

Valine in its "L-" form, L-Valine, is an essential amino acid. It is one of the three amino acids which are called the branched chain amino acids (BCAA). BCAA's make up about 50% of the indispensable amino acids in the daily food supply. BCAA's are rather unique in that skeletal muscles may directly use them as an energy source as they are an anabolic substance which promotes protein synthesis. BCAA's are used up in stressful conditions more rapidly than other amino acids.

In controlled research experiments at the Brain-Bio Center in Princeton, New Jersey and elsewhere, removal of valine from the diet was thought to result in some noticeable but reversible changes to the red nuclei of the brain and the chief protein synthesizing machinery of the cells of the body. Deficiency of this and other amino acids causes the malabsorption of dietary nitrogen and protein. Valine is believed vital for mental function, muscle coordination, and neural functioning.