Does taking glutathione make sense, or is it broken down in your gut?
Oral glutathione measurably raises levels in blood and cells, so it is not entirely pointless. Whether that rise translates into tangible health benefits has not yet been properly studied.
Yes, oral glutathione does reach the body, although some of it is broken down in the gut. A double-blind study in 54 healthy adults compared six months of daily supplementation at 250 or 1000 mg against a placebo. After six months, glutathione levels in red blood cells and whole blood rose by 17 to 29% in the low-dose group, and by 30 to 35% across multiple blood cell types in the high-dose group. In cheek lining cells, the increase reached as high as 260%. So a meaningful amount does get through.
A higher level is not the same as a health benefit: whether you actually feel better or get sick less often as a result has not been studied. For that reason, it is not yet worth your money. If you do want to try it, look for 'L-glutathione (reduced)' on the label. In the study, 1000 mg per day produced the largest increase, and that increase only appeared after 3 to 6 months. One month after stopping, levels in the study had already returned to baseline, so you need to keep taking it to maintain any effect. When the best time to take it is, and whether food affects absorption, cannot be determined from the research.
For skin lightening, the evidence is too weak to make a recommendation. A review of four small studies found a trend toward reduced pigmentation on sun-exposed skin with 500 mg per day taken orally or a cream containing 2.0% oxidised glutathione, but the researchers described the study quality as too low for firm conclusions. On sun-protected skin, no product made any difference. Effects on wrinkles and skin texture remained unproven.
Whether glutathione works as well as other ways of boosting the body's supply, for example via NAC (a building block for glutathione), cannot be compared on the basis of the available studies. That remains an open question.
All claims are based on one RCT (PMID 24791752, n=54) and one systematic review of four small studies (PMID 30895708). The number of participants and studies is limited; larger independent replication is lacking.
Does taking iron help, or is it actually a risk?
Taking iron clearly helps if you have a deficiency or anaemia, but is pointless and potentially risky if that is not the case. Have your iron levels checked before starting supplements.
Does taking vitamin E have any proven benefit?
For the most widely studied application, the heart, vitamin E demonstrably does not work; for skin and fertility the evidence is too thin to say it helps, so there is no clear reason to take it.
Is curcumin well absorbed by your body?
Ordinary curcumin without any addition is barely absorbed by the body; choose a product with piperine (black pepper extract) or a specialised formulation to notice any effect.
Do you lose muscle mass when losing weight with a GLP-1 medication, and how do you prevent it?
With GLP-1 medications you do indeed lose muscle mass alongside fat, but you can largely limit this by combining resistance training with adequate protein intake. If you are older or already frail, discuss this risk explicitly with your doctor before starting.
Does taking resveratrol make sense as an anti-ageing strategy?
For humans there is no convincing evidence that resveratrol supplements do anything against ageing; the animal research is interesting but has not yet translated into clinical practice, so hold off on supplements until better human data are available.
Is taking a stack of supplements at the same time smart or actually dangerous?
Whether a supplement stack is smart or dangerous depends on which substances you combine and whether you also use medications. Always tell your doctor or pharmacist what you are taking, and be especially cautious with St. John's wort and goldenseal.