Supposed to utilize the methyl better. More for your money if taken (explains better in Designer Supps article). I've done it and it works I believe. Also, I feel much more effect if I take it 30-45 mins before the dosing, instead of at the same time. I was almost done with 2 weeks cycle 200mcg/day of clen and by then I don't sweat or get the jitters, but when used the grapefruit juice 30 mins before I was sweatin balls all night. So I am a believer in the grapefruit juice theory.