Does red light therapy really have an effect on your cells?
Red light therapy has a biologically plausible effect on cells, with positive clinical indications for pain and recovery, but standard doses are lacking and home devices have not been sufficiently studied. Interest is justified, but keep your expectations realistic until more standardised research is available.
Red light therapy (also known as photobiomodulation) has a clear biological mechanism of action. An enzyme in the mitochondria, the energy factories of your cells, absorbs red and near-infrared light. This leads to greater production of ATP (the cell's energy carrier), changes in signalling molecules, and a higher voltage across the mitochondrial membrane. This has been demonstrated in cell and animal research, and the mechanism is widely recognised.
Clinically, there are positive results for pain reduction, wound healing, and inflammation control. However, the studies are difficult to compare with one another, because there are no standard protocols for wavelength, dose, or treatment duration. What works in one protocol does not necessarily work in another. A small study in healthy individuals also showed a remarkable effect on blood sugar: 15 minutes of exposure to red light (670 nm) reduced the blood sugar spike after glucose intake by nearly 28%. That is an interesting finding, but it has not yet been confirmed in larger groups or at-risk populations.
An underappreciated risk is too much light. Higher doses actually reverse or negate the effect. Cells with many mitochondria, such as those in muscles, the brain, and the heart, respond at relatively low doses already. Overdosing appears to be more often the problem in failed studies than underdosing.
For home users there is an additional caveat: most clinical evidence comes from laser research, while consumer devices almost always use LED diodes. Whether these produce the same effect has not been demonstrated. Regulatory standards for such devices are also largely absent, making it difficult to draw firm conclusions about effectiveness and safety at home. Skin redness is the most commonly reported side effect and resolves on its own; serious side effects have not been described in the reviewed literature.
This answer is based on multiple reviews, a systematic review with summarised studies, and a small human study on blood sugar. The mechanism in cells is well documented; clinical evidence in humans is promising but has not yet been standardised. The evidence for home devices is the weakest.
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.
Can heat, such as a sauna, damage your cells or actually make them stronger?
Moderate heat briefly damages cells, but simultaneously triggers a repair response that makes the cell more resilient. Repeated sauna use appears beneficial for inflammation levels, immune function, and possibly blood sugar as well, but large randomised studies are still lacking.
Can fasting really rejuvenate your cells?
Fasting has clear cell-rejuvenating effects in animal research, but in humans the evidence is still limited to small studies using biomarkers. The most promising findings have not yet been confirmed in large human studies, so caution is warranted.
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.
What is young blood / plasma exchange, and does it actually work?
Plasma exchange clearly works in mice, but in humans there is still no evidence whatsoever of efficacy or safety. Do not be tempted by commercial providers offering young plasma as a rejuvenation treatment.
Can stem cell therapy slow down or cure rheumatoid arthritis?
Stem cell therapy may be able to slow the symptoms of rheumatoid arthritis, but it does not cure it. The research is still too limited for firm conclusions, so if you are interested, discuss it with your rheumatologist.