10.1073/pnas.95.4.1852 125
Here's the TL;DR on vitamin timing: while there is no official medical advice dictating that you should take vitamin supplements at a specific time of day to improve their efficiency, there is quite a lot of research showing that avoiding some vitamin supplements at particular times (or more accurately, with particular meals) can improve absorption, or that taking some vitamins alongside food can reduce the risk of adverse side effects
Oxidation of GSH to GSSG results in dysregulation of the intracellular redox imbalance (decreased GSH:GSSG ratio), which is associated with oxidative stress and DNA damage in fibroblasts (Asensi et al., 1999)
They are often sufficient for correcting mild dietary deficiencies (e.g., in vegans who dont consume fortified foods) and can sometimes be used for maintaining levels after an initial course of injections, provided absorption is adequately monitored by a healthcare professional
Whereas in Mexico the frequency of the deficiency was between 0.4% and 4.1%, in Cuba it was 4.9% with a prevalence of the variant A-, and 7% for the A+ variant 40
