Research questions
Every research question on this site, with the short answer beside it.
19 questions answered
Every answer here is a sentence we published ourselves, word for word, with the piece it came from. Nothing is summarised and nothing is assembled out of two articles. Where we have not looked into something, it says so.
We write per question, not per subject. This is the list: what was asked, what came out, and how solid that is. Follow one through for the whole thing, including the research that found nothing.
Body
Does sauna make you live longer?
The famous Finnish figures compare frequent sauna users with infrequent ones, not with people who never go, so they cannot answer that.
Limited
Environment
What does blue light do to your circadian rhythm?
It suppresses melatonin and shifts your clock. But how much light there is and when weigh more than its colour, and people differ more than lamps do.
Strong
Do blue light glasses help with tired eyes?
Your eyes can genuinely feel calmer, but not because of the blue. A grey lens of the same darkness did exactly the same.
Limited
Do blue light glasses help you sleep?
Probably not if you already sleep reasonably well. Possibly if you have a sleep problem such as insomnia, shift work or jet lag.
Weak
Is light therapy safe if you have or have had cancer?
The clinical evidence in patients is reassuring. The worry comes almost entirely from cell cultures. Nobody has measured recurrence in the irradiated area.
Limited
Does red light on your head help your memory?
Meta-analyses say yes for cognition, and a home device has now been tested too. The effect is real but the literature behind it is small.
Reasonable
Is red light bad for your eyes?
Thousands of children have had it shone straight into their eyes for myopia and the safety record held. The harm cases came from heat lamps, not from therapy devices.
Reasonable
Does red light work for pain?
For most conditions the reviews contradict each other. For low back pain, Cochrane found no clinical effect at all.
Limited
Does red light help wounds heal?
In diabetic foot ulcers it nearly doubles the chance of healing. In venous leg ulcers it does nothing. It depends entirely on the wound.
Reasonable
What do red and near-infrared light actually do?
The same narrow recipe keeps turning up where it works: roughly 660 to 830nm at a low dose. It is not equally supported for everything it is sold for.
Limited
Longevity
Which health tracker is accurate, which of its numbers can you trust, and is wearing one around the clock harmful?
The measurement matters more than the brand: heart rate, rhythm and steps hold up, while sleep staging, calories, exercise intensity and VO2max do not. Roughly one tracker in nine has ever been validated for anything. On safety, the documented harm is to skin, from nickel and acrylates rather than from anything the sensor emits, and the radio exposure measures at about a hundredth of the limb limit. Whether a green light against your skin for years matters has never been studied at all.
Reasonable
Can you measure your biological age?
Yes, from nine standard blood values, and it predicts death better than your calendar age does. It is not a reading of your cells.
Reasonable
Nutrition
How harmful are sugar-sweetened drinks?
Enough to act on, and not so much that one glass breaks anything. Per daily glass added: 0.83 kg in the trials, 27 percent more type 2 diabetes in the cohorts, and per 250 ml a day, 17 percent more coronary heart disease.
Reasonable
Is chewing gum bad for you, and does your body think you are eating?
Partly yes. Chewing does fire the reflex: saliva, gut hormones and a nerve signal to the gut. Insulin is the part that does not follow. In the trial that measured it during half an hour of chewing on an empty stomach, insulin, glucose and GIP did not move, and in a trial where gum was chewed before a meal the glucose rise afterwards was smaller.
Limited
What does nattokinase do?
It lowers clotting factors consistently and blood pressure modestly. On its own it does nothing for cholesterol, and the plaque result rests on a single trial.
Limited
What is actually in a supplement?
Often not what the label says. Published analyses of commercial products keep finding contents that do not match, and undeclared pharmaceutical substances in plant products.
Laboratory analysis of products
Sleep
Is the radiation from a phone next to your bed bad for your sleep?
In the largest studies, the ones that measured exposure instead of asking about it, the radiation shows up as nothing. The device shows up as something, and nearly all of it is the time you spend using it in bed.
Reasonable
Movement
Do posture correctors work?
Nobody knows, because the strap being sold to you has never been tested. In the one sham trial, the fake shirt outperformed the real one.
Weak
Is grip strength an indicator of longevity?
It predicts death better than blood pressure does, but it is a readout of whole-body strength rather than a cause. Training only your grip will not extend your life.
Limited