The claim: Avoid sunscreen
Is sunscreen bad for you?
Against: the one trial runs the other way. Evidence grade: Probable, a single trial with few melanomas.
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The book tests this claim twice, in a table and in the chapter that owns the subject. Both verdicts are below, each with its own evidence and sources.
Chapter 2's table of nine claims: "Avoid sunscreen"
Against: the one trial runs the other way
The evidence
An Australian trial assigned adults to use sunscreen daily or at their own discretion. Over long follow-up the daily group had three invasive melanomas, the most dangerous skin cancer, against eleven in the other group (Chapter 7).25
The "What you've heard" box in Chapter 7: "Sunscreen is dangerous, and you are better off without it"
The danger claim is unsupported, and the one long trial runs the other way
The evidence
In trials run by the US Food and Drug Administration, heavy, repeated use put several chemical filters into the blood above the level that prompts further safety testing. The agency has not concluded that those ingredients are unsafe. Against that sits a randomized trial in Nambour, Queensland, where adults were assigned to put on sunscreen every day or as they pleased. The daily group developed about two-fifths fewer squamous cell tumors, though no fewer people got one, and a decade after the trial ended, it had three invasive melanomas against eleven, a small count.19 If the worry is vitamin D, a daily supplement settles it without giving up sunscreen. If you want less on your skin, lean on shade, clothing and a hat first.
Where the book tests it
Related claims
- Is mouth taping safe, and does it work?Unsupported, with a safety catch.Evidence grade: Emerging. Early, small, animal-only, or actively contested.
- Do blue light glasses work for sleep?Mostly unsupported; skip the glasses unless a clinician suggests them for a specific sleep problem.Evidence grade: Strong. Multiple randomized controlled trials, or consistent large cohort studies with a well-understood mechanism.
- Does ten minutes of morning sunlight set your body clock?Right direction, invented number.Evidence grade: Probable. Good observational evidence with a plausible mechanism, or small or few trials.
- Should you wait 90 minutes after waking for coffee?Untested, and the reasoning looks backward.Evidence grade: Emerging. Early, small, animal-only, or actively contested.
- Do tart cherry juice and magnesium help you sleep?Unproven.Evidence grade: Emerging. Early, small, animal-only, or actively contested.
- Can NSDR or yoga nidra replace lost sleep?A pleasant way to rest, not a substitute for sleep.Evidence grade: Emerging. Early, small, animal-only, or actively contested.
Sources
Chapter 2's table of nine claims
- 25.Green, A.C., Williams, G.M., Logan, V., and Strutton, G.M. (2011). "Reduced melanoma after regular sunscreen use: randomized trial follow-up." Journal of Clinical Oncology, 29(3), 257-263. https://doi.org/10.1200/JCO.2010.28.7078 (the Nambour trial: 1,621 adults randomized in 1992-96 and followed to 2006; hazard ratio for invasive melanoma 0.27, 95% CI 0.08-0.97)
Note numbers are those of Chapter 2, What Your Body Expects, and How to Trust This Book.
The "What you've heard" box in Chapter 7
- 19.Matta, M.K., Zusterzeel, R., Pilli, N.R., Patel, V., et al. (2019). "Effect of sunscreen application under maximal use conditions on plasma concentration of sunscreen active ingredients: a randomized clinical trial." JAMA, 321(21), 2082-2091. https://doi.org/10.1001/jama.2019.5586 ; U.S. Food and Drug Administration (2026). Questions and answers: FDA's regulatory actions on over-the-counter sunscreen. https://www.fda.gov/drugs/understanding-over-counter-medicines/questions-and-answers-fdas-regulatory-actions-over-counter-sunscreen ; Green, A., Williams, G., Neale, R., Hart, V., et al. (1999). "Daily sunscreen application and betacarotene supplementation in prevention of basal-cell and squamous-cell carcinomas of the skin: a randomised controlled trial." The Lancet, 354(9180), 723-729. https://doi.org/10.1016/S0140-6736(98)12168-2 (1,621 adults. Tumors, rate ratio 0.61; people with a new squamous cell cancer, 0.88, 95% CI 0.50-1.56.) ; Green, A.C., Williams, G.M., Logan, V., and Strutton, G.M. (2011). "Reduced melanoma after regular sunscreen use: randomized trial follow-up." Journal of Clinical Oncology, 29(3), 257-263. https://doi.org/10.1200/JCO.2010.28.7078 (Invasive melanoma hazard ratio 0.27, 95% CI 0.08-0.97; all melanomas 0.50, 0.24-1.02.)
Note numbers are those of Chapter 7, Light and Dark.
This verdict is one of nine in the table Chapter 2 uses to show how the book judges a claim: find the primary study, and grade the claim by what it measured. The grade rates the evidence behind the verdict, by the book's stated method.
Educational content, not medical advice. Disclaimer.