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.
Pregnant women and people with iron-deficiency anaemia benefit the most from iron supplementation. Daily iron raises haemoglobin levels and reduces the risk of anaemia in infants, school-age children, and both pregnant and non-pregnant women. This has been demonstrated in a large overview of 75 systematic reviews. Preventive supplementation during pregnancy is therefore recommended for all pregnant women, regardless of region.
If you have an iron deficiency without anaemia, supplementation can reduce your fatigue. Four randomised trials involving more than 700 participants found a small to moderate effect on self-reported fatigue. However, iron has no demonstrable effect on athletic performance in that situation: maximum oxygen uptake did not change.
A real drawback is that iron tablets frequently cause gastrointestinal complaints, such as nausea and an unpleasant feeling in the stomach. This sometimes leads people to take them inconsistently, which makes the treatment less effective. For pregnant women who experience daily side effects, taking them less frequently can help, but that in turn raises the risk of anaemia around the time of delivery. It is therefore a trade-off.
For some groups the situation is especially complex. People with chronic kidney disease need iron supplementation, but overly generous use carries risks. In vegan children the risk of iron deficiency is greater, because plant-based iron is absorbed less efficiently. And for premature infants, European guidelines recommend supplementation until at least one year after the original due date. In all these cases, medical supervision is essential.
What you should never do without good reason is take extra iron if you have no deficiency. Healthy adults with adequate iron status gain no benefit from it. Moreover, too little is known about the risks of prolonged excess iron during pregnancy to formulate sound guidelines. Have your iron levels measured before starting supplements.
Based on a Cochrane umbrella review (75 SRs, PMID 34564844), multiple systematic reviews, and European guidelines. The total number of participants across the studies is difficult to determine precisely; the umbrella review covers tens of thousands of participants. The claim regarding fatigue in iron deficiency without anaemia (IDNA) is based on 4 RCTs with 714 participants (PMID 29626044).
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.
Can you take too much magnesium?
Yes, too much magnesium can be dangerous, although serious toxicity from ordinary supplements is rare in people with healthy kidneys. With kidney problems or when using intravenous magnesium, medical supervision is genuinely necessary.
Should you take extra copper when taking high doses of zinc?
Anyone who takes more than 25-40 mg of zinc per day for an extended period runs a real risk of copper deficiency with sometimes serious consequences. Have your blood values checked and always discuss high zinc doses with your doctor.
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.
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.
Is intermittent fasting good for longevity?
Intermittent fasting improves health markers such as weight and insulin sensitivity, but whether it also makes you live longer has not yet been proven in humans. It is worth considering, but discuss it with your doctor first if you belong to a risk group.