A 2021 study focusing on the effects of L-theanine on cognitive function in older adults appears to support this
They found that vitamin D levels [25(OH)D] were positively associated with plasma glutathione (as vitamin D levels increased so did glutathione) and negatively associated with both GSSG and cysteine (as vitamin D levels increased, levels of GSSG and cysteine decreased)
CrossRef Salvage Treatment with Low-Dose Weekly Paclitaxel in Elderly or Poor Performance Status Patients with Metastatic Urothelial Carcinoma Jae Joon Han, Yu Jung Kim, Jin Won Kim, Hyun Chang, Jeong-Ok Lee, Keun-Wook Lee, Chang Wook Jeong, Jee Hyun Kim, Sung Kyu Hong, Soo-Mee Bang, Seok-Soo Byun, Sang Eun Lee, Jong Seok Lee Tumori Journal.2014
Withdrawing a smaller or larger aliquot changes the absolute mass of every component simultaneously, but the ratio between them stays locked at 5:1:1:1