The subject invention provides therapeutic compositions and uses thereof for improving pulmonary function. In one embodiment, the therapeutic composition comprises one or more free amino acids selected from lysine, glycine, threonine, valine, tyrosine, aspartic acid, isoleucine, tryptophan, asparagine, and serine and electrolytes. In one embodiment, the subject invention can be used to prevent or treat long-term lung complications induced by radiation.