mainly it gives you bad dreams and makes you need to sleep less.
not all bad, but you can get plenty in eggs, pork and chicken
Discussion
also, if you want to remember dreams, 500mg of phenylalanine or tyrosine will do the trick. you won't forget one dream all night.
if you want your dreams to be even weirder, try taking 5x recommended dose of melatonin.
i've done both, and i think i preferred the amino acid.