Short Answer: BH4 is expensive and requires very high doses, so if the problem is modest it can much more easily be solved by taking tyrosine. Watch the video or listen to the podcast with the links below. You can obtain a full transcript of the episode by signing up for the Masterpass at https://chrismasterjohnphd.com/q&a Please consider supporting my work by making a purchase using these links at one of my affiliates: https://chrismasterjohnphd.com/foursigmatic, https://chrismasterjohnphd.com/paleovalley, https://chrismasterjohnphd.com/seekinghealth, https://chrismasterjohnphd.com/ancestralsupplements, https://chrismasterjohnphd.com/magicspoon, https://chrismasterjohnphd.com/lmnt  Plenty more at https://chrismasterjohnphd.com/support! If you would like to be part of the next live Ask Me Anything About Nutrition, sign up for the CMJ Masterpass, which includes access to these live Zoom sessions, premium features on all my content, and hundreds of dollars of exclusive discounts. You can sign up with a 10% lifetime discount here: https://chrismasterjohnphd.com/q&a DISCLAIMER: I have a PhD in Nutritional Sciences and my expertise is in performing and evaluating nutritional research. I am not a medical doctor and nothing herein is medical advice.