Question: Are bilirubin and uric acid useful markers of antioxidant defense and oxidative stress? What are better markers?
I think intracellularly where most of antioxidant support is highly relevant, then they're not that big a deal. In the plasma, they can be a big deal. It's quite possible that uric acid is one of the most important antioxidants in plasma. But I would say it's highly debatable whether we put uric acid into the blood specifically to achieve that versus that happens to be an accidental sort of just incidental to making uric acid during the excretion of purines, which make up the building blocks of DNA and ATP and things like that.
I think the best marker of oxidative stress in plasma is the cysteine to cystine ratio. Cysteine is the reduced form of the amino acid cysteine. Cystine is the oxidized form. There are good studies at a general population level showing that that is the major specific indicator of oxidative stress that takes place in the plasma.
The glutathione couple, glutathione reduced versus oxidized, is probably the best marker in the blood of what's happening with oxidative stress intracellularly. Unfortunately, the only test that looks at this is HDRI. I feel very, very torn about whether we should be working with HDRI because I know a lot about measuring glutathione. I've had some clients who got their glutathione test. What you need to do to accurately measure glutathione to preserve the sample, according to my client who did the test, is not at all part of the instructions or process that they use, so I am very skeptical of using them. No one else offers the reduced to oxidized version of glutathione.
So, what I would recommend to assess oxidative stress would be Genova's Oxidative Stress 2.0 panel. It does give you the cysteine to cystine ratio. I'll put a note to put a link to that in the show notes. I think that's the best marker. They do have glutathione on there, and they do have a bunch of other things that can be useful in assessing oxidative stress. I would use that.
This Q&A can also be found as part of a much longer episode, here: https://chrismasterjohnphd.com/podcast/2019/09/06/ask-anything-nutrition-march-8-2019
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