Does taking vitamin E have any proven benefit?
For the most studied applications, cardiovascular disease, 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.
Vitamin E has no proven effect on cardiovascular disease. An analysis of 884 randomised trials involving more than 880,000 participants found no statistically significant benefit whatsoever in the area of cardiovascular disease or type 2 diabetes. The same conclusion applies after a heart attack: in a large trial with more than 11,000 patients, vitamin E offered zero percent risk reduction for death, a new heart attack or stroke, while fish fatty acids in that same study did work.
In the area of skin health, the picture is less clear-cut. A broad literature review describes possible positive effects, such as protection against UV damage and some benefit in eczema. But those findings have not been established quantitatively, there is no consensus on the correct dosage, and the quality of the research leaves much to be desired. You cannot yet speak of proven benefit here.
For fertility problems in women, there is a Cochrane analysis of 63 trials that provides indications that antioxidants as a group can slightly increase the chance of pregnancy (from roughly 19% to 25-30%). Vitamin E was one of the substances in that group, but the effect was not broken down per substance. The quality of the evidence was low to very low, so no separate conclusion can be drawn from this for vitamin E.
Four claims used: one large meta-analysis (PMID 36480969), one large RCT (PMID 10465172), one narrative review on skin (PMID 38256329), one Cochrane review on antioxidants/fertility (PMID 32851663).
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.
Do you really need electrolyte supplements?
For shorter workouts you do not need electrolyte supplements; for endurance exercise lasting longer than 90 minutes, sports drinks containing sodium and carbohydrates can be beneficial, but drinking too much is a real risk.
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.
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 also produces tangible health benefits has not yet been properly studied.
Does echinacea really work against the common cold?
Echinacea has not been proven effective against the common cold. If you still want to try something, Echinacea purpurea (above-ground parts) has the most, though still mixed, indications for early use at the onset of a cold.
Does ergothioneine work as a longevity supplement?
Ergothioneine shows a positive signal in a small study of older adults with memory complaints, but it is too early for firm recommendations. Eating mushrooms is a risk-free way to obtain the compound; a supplement is worth considering only once larger studies provide greater clarity.