Does echinacea really work against the common cold?
Echinacea does not work the same way for all preparations: root extracts do not appear to help, but some standardised preparations of Echinacea purpurea (herb plus root) showed a modest effect in smaller studies. What you buy in a shop rarely corresponds to the products tested in the positive studies.
Nearly 400 volunteers took part in a well-designed study published in the New England Journal of Medicine, in which three chemically characterised extracts of Echinacea angustifolia root were tested, both for prevention and as treatment. None of the three extracts had any demonstrable effect on the likelihood of catching a cold, the severity of symptoms, nasal secretion or inflammatory markers.
Yet it is not a simple 'does not work'. A study with 246 participants found that a specific standardised preparation of Echinacea purpurea (herb plus root) reduced the symptom index significantly more than placebo. A liquid preparation with a defined composition of active substances showed a 23% lower symptom score compared with placebo. Pure root extract from the same plant, however, had no effect. The brand, the plant species and the part of the plant used (herb versus root) therefore make a large difference.
A Cochrane review of 16 studies with a total of 3396 participants draws a cautious conclusion: some preparations appear to work better than placebo, but the evidence is too inconsistent to recommend any single specific product. Another literature review of clinical research conducted between 1961 and 1999 confirms that picture: twelve studies reported positive effects, five later studies yielded mixed results. Study shortcomings and non-standardised preparations make the outcomes difficult to compare.
Safety does not appear to be a major concern: no harm was identified in the studies. Practically speaking, however, the problem is that most products available in shops do not correspond to the standardised preparations used in the positive studies. Anyone wishing to try echinacea would do best to choose a preparation of Echinacea purpurea (herb including root) with a known composition, and to start taking it early at the first sign of symptoms.
This answer is based on eight studies, including one large well-designed study (published in the New England Journal of Medicine, with nearly 400 participants) and a Cochrane review of 16 studies with 3396 participants. The large study showed no effect for root extract of Echinacea angustifolia. Smaller studies using other preparations did find positive effects. The evidence is therefore mixed and highly dependent on which preparation was tested: the researchers themselves emphasise that study shortcomings, non-standardised products and varying plant species make comparison difficult.
Does quercetin work against ageing and inflammation?
Quercetin shows promising signals in the laboratory and in animals, but in humans there is not yet solid evidence. Taking supplements on the basis of this early-stage research gets too far ahead of the science.
Does ashwagandha really work against stress?
Ashwagandha demonstrably lowers the stress hormone cortisol, but whether it actually makes you feel better has not yet been convincingly proven. Short-term use (up to around 12 weeks) appears to be safe, but too little is known about long-term use to be certain.
Is curcumin well absorbed by the body?
Standard curcumin is barely absorbed, but combining it with piperine (black pepper) dramatically increases absorption in humans. When choosing a curcumin supplement, opt for a product containing piperine or a modern formulation, and check whether independent human research backs it up.
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 stem cell therapy work against ageing in humans?
For one specific application, physical frailty in older adults, there is a first randomised trial with a positive result; for all other ageing-related applications it is too early for firm statements, and stem cell therapy cannot yet be considered a proven anti-ageing treatment.
Do functional mushrooms like reishi and cordyceps actually work?
Medicinal mushrooms such as reishi show promising effects in the laboratory, but convincing evidence in humans is still lacking. Also check the species: cordyceps of the species Cordyceps militaris (the form most supplements use) is not authorised in the EU and may not be sold — the Dutch NVWA removed these products from the market in 2025. If you use medications, always consult your doctor first.