You can do other things too from what I've read in the research - but your body will just decrease it's natural output during the remaining 24 hour cycle. 3g of GABA before resistance training will raise it. I definitely would not spend money on some fancy 'natural formula' that supposedly does it - the "study/ies" those are based on, are severely lacking.
MK-677 is the only "swallow it" thing that actually works well, but even it requires a looooooooong period of administration for benefits to be seen, and from what I'm seeing written, to get ANABOLIC (not general health, well being, anti-aging), you need to add Peptides to it.