A NOVEL WAY TO PRESERVE BH4
Based on a simple yet powerful concept in the paper referenced below, i have found that supplementing between meals with an essential amino acid mix, minus Phenylaline, and optionally Tyrosine and Tryptophan can help preserve BH4 levels.
The simple formulae i have found helpful helping to preserve BH4 is first without Phenylalinine, is a mix of : Leucine (3g), Iso-Leucine (1.5g), Valine (1.5g), Lysine (1.0-1.25 g), Histadine (1g), Threonine (1g), Methionine (0.5g), Tryptophan (0.5g). If you also feel the need to support dopamine, simply add in Tyrosine [.5g].
I have found this effective to lowering the drain on BH4 as it is required to synthesize Tyrosine from Phenylalinine. The study referenced here, was focused on lowering neurotransmitter levels by reducing the pre-cursors: Phenylalinine, Tryptophan and Tyrosine - the results speak to its effectiveness and speed.
 A new method for rapidly and simultaneously decreasing serotonin and catecholamine synthesis in humans. Marco Leyton, PhD; Valerie Kwai Pun, BSc; Chawki Benkelfat, MD, DERBH; Simon N. Young, PhD Department of Psychiatry, McGill University, Montréal, Que. J Psychiatry Neurosci 2003;28(6):464-7. Submitted Oct. 23, 2002 Revised Jan. 15 2003; Mar. 6, 2003 Accepted Mar. 21, 2003. 2003 Canadian Medical Association.