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  • Bonus: Sugar Sag with Commentary

    Bonus: Sugar Sag with Commentary
    Jan 12 2026
    While we’re on a short break between seasons, we’re revisiting some of our favorite episodes from Season 1. This week, we’re re-releasing our exploration of how your diet can affect your skin – now with added commentary!Wrinkles and sagging skin—just normal aging, or can you blame your sweet tooth? We dive into “sugar sag,” exploring how sugar, processed foods, and even your crispy breakfast toast might be making you look older than if you’d said no to chocolate cake and yes to broccoli. Along the way, we encounter statistical adjustment, training and test data sets, what we call “references to nowhere,” plus some cadavers and collagen. Ever heard of an AGE reader? Find out how this tool might offer a sneak peek at your date’s age—and maybe even a clue about his… um… “performance.”Statistical topics ConfoundingCorrelation vs causationMeasurement error / proxy variablesOverfitting PlagiarismProper citing practicesReferences to nowhereStatistical adjustmentTraining and test setsMethodologic morals“When you plagiarize, you steal the errors too.”“Overdone statistical adjustment is like overdone photo filters–at a certain point it’s just laughable.”CitationsCollagen turnover: Verzijl N, DeGroot J, Thorpe SR, et al.Effect of Collagen Turnover on the Accumulation of Advanced Glycation End Products. JBC. 2000;275:39027-31.Cadaver study:Hamlin CR, Kohn RR, Luschin JH. Apparent Accelerated Aging of Human Collagen in Diabetes Mellitus. Diabetes. 1975; 24: 902–904.AGE ReaderStudies of AGEs and diabetes and health:Monnier VM, Cerami A. Nonenzymatic browning in vivo: possible process for aging of long-lived proteins. Science. 1981;211:491-3. Brownlee M, Vlassara H, Cerami A. Nonenzymatic glycosylation and the pathogenesis of diabetic complications. Ann Intern Med. 1984;101:527-37. Monnier VM, Vishwanath V, Frank KE, et al. Relation between Complications of Type I Diabetes Mellitus and Collagen-Linked Fluorescence. N Engl J Med. 1986;314:403-408.Monnier VM, Sell DR, Abdul-Karim FW, et al. Collagen browning and cross-linking are increased in chronic experimental hyperglycemia. Relevance to diabetes and aging. Diabetes. 1988;37:867-72. Monnier VM, Bautista O, Kenny D, et al. Skin collagen glycation, glycoxidation, and crosslinking are lower in subjects with long-term intensive versus conventional therapy of type 1 diabetes: relevance of glycated collagen products versus HbA1c as markers of diabetic complications. Diabetes 1999; 48: 870–80.Genuth S, Sun W, Cleary P, et al. Glycation and carboxymethyllysine levels in skin collagen predict the risk of future 10-year progression of diabetic retinopathy and nephropathy in the diabetes control and complications trial and epidemiology of diabetes interventions and complications participants with type 1 diabetes. Diabetes. 2005;54:3103-11. van Waateringe RP, Slagter SN, van Beek AP, et al. Skin autofluorescence, a non-invasive biomarker for advanced glycation end products, is associated with the metabolic syndrome and its individual components. Diabetol Metab Syndr. 2017;9:42. Kouidrat Y, Zaitouni A, Amad A, et al. Skin autofluorescence (a marker for advanced glycation end products) and erectile dysfunction in diabetes. J Diabetes Complications. 2017;3:108-113. Fujita N, Ishida M, Iwane T, et al. Association between Advanced Glycation End-Products, Carotenoids, and Severe Erectile Dysfunction. World J Mens Health. 2023;41:701-11. Uruska A, Gandecka A, Araszkiewicz A, et al. Accumulation of advanced glycation end products in the skin is accelerated in relation to insulin resistance in people with Type 1 diabetes mellitus. Diabet Med. 2019;36:620-625. Boersma HE, Smit AJ, Paterson AD, et al. Skin autofluorescence and cause-specific mortality in a population-based cohort. Sci Rep 2024;14:19967.Review article with conflicts of interest: Draelos ZD. Sugar Sag: What Is Skin Glycation and How Do You Combat It? J Drugs Dermatol. 2024; 23:s5-10.Clinical study on AGE interrupter cream:Draelos ZD, Yatskayer M, Raab S, Oresajo C. An evaluation of the effect of a topical product containing C-xyloside and blueberry extract on the appearance of type II diabetic skin. J Cosmet Dermatol. 2009;8:147-51. Our citation trail:2023 review article: Zgutka K, Tkacz M, Tomasiak, et al. A Role for Advanced Glycation End Products in Molecular Ageing. Int J Mol Sci. 2023; 24: 9881. Sentence: “Interestingly, strict control of blood sugar for 4 months reduced the production of glycosylated collagen by 25%, and low-sugar food prepared by boiling could also reduce the production of AGEs [152].”Reference 152 is a review article: Cao C, Xiao Z, Wu Y, et al. Diet and Skin Aging-From the Perspective of Food Nutrition. Nutrients. 2020;12:870. Sentence: “However, strict control of blood sugar for four months can reduce the production of glycosylated collagen by 25%, and low-sugar food prepared by boiling can also reduce the production of AGEs [93–...
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    1 Std. und 14 Min.
  • Bonus: Vitamin D Part 1 with commentary

    Bonus: Vitamin D Part 1 with commentary
    Dec 29 2025
    While we’re on a short break between seasons, we’re revisiting some of our favorite episodes from Season 1. This week, we’re re-releasing our deep dive into vitamin D and the origins of the so-called deficiency epidemic, with added commentary.Is America really facing an epidemic of vitamin D deficiency? While this claim is widely believed, the story behind it is packed with twists, turns, and some pesky statistical cockroaches. In this episode, we’ll dive into a study on Hawaiian surfers, expose how shifting goalposts can create an epidemic, tackle dueling medical guidelines, and flex our statistical sleuthing skills. By the end, you might wonder if the real deficiency lies in the data.Statistical topicsconflicts of interestcut points and thresholdsdichotomizationincentives in sciencemeasurement and classificationnormal distribution researcher biasesstandard deviationstatistical sleuthingMethodologic morals“Arbitrary thresholds make for arbitrary diseases.”“Statistical errors are like cockroaches: Where there’s one, there’s many.”Note that all blood vitamin D levels discussed in the podcast are 25-hydroxyvitamin D levels given in units of ng/ml. To convert from ng/ml to nmol/L, use the formula: nmol/L=2.5*ng/ml. For example, a vitamin D level of 30 ng/mL corresponds to 75 nmol/L.CitationsDr. Rhonda Patrick: Micronutrients for Health & Longevity. Huberman Lab Podcast. May 1, 2022Noh CK, Lee MJ, Kim BK, et al. A Case of Nutritional Osteomalacia in Young Adult Male. J Bone Metab. 2013; 20:51-55.Binkley N, Novotny R, Krueger D, et al. Low vitamin D status despite abundant sun exposure. J Clin Endocrinol Metab. 2007;92:2130-5. Malabanan A, Veronikis IE, Holick MF. Redefining Vitamin D Insufficiency. Lancet. 1998;351:805-6. Dawson-Hughes B, Heaney RP, Holick MF, et al. Estimates of optimal vitamin D status. Osteoporos Int. 2005;16:713-6.Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357:266-81.Cui A, Xiao P, Ma Y, et al. Prevalence, trend, and predictor analyses of vitamin D deficiency in the US population, 2001-2018. Front Nutr. 2022;9:965376. Ross AC, Manson JE, Abrams SA, et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab. 2011;96:53-8. Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2011;96:1911-30. Manson JE, Brannon PM, Rosen CJ, et al. Vitamin D deficiency-is there really a pandemic. N Engl J Med. 2016;375:1817-20. Conti G, Chirico V, Lacquaniti A, et al. Vitamin D intoxication in two brothers: be careful with dietary supplements. J Pediatr Endocrinol Metab. 2014;27:763-7.Holick, Michael, et al. The UV Advantage. Ibooks, 2004.Holick, Michael F. The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problems. Penguin Publishing Group, 2011.Szabo, Liz. Vitamin D, the Sunshine Supplement, Has Shadowy Money Behind It. The New York Times. August 18, 2018.Lee JM, Smith JR, Philipp BL, Chen TC, Mathieu J, Holick MF. Vitamin D deficiency in a healthy group of mothers and newborn infants. Clin Pediatr. 2007;46:42-4. Holick MF. Vitamin D deficiency: what a pain it is. Mayo Clin Proc. 2003;78:1457-9.Passeri G, Pini G, Troiano L, et al. Low Vitamin D Status, High Bone Turnover, and Bone Fractures in Centenarians. J Clin Endocrinol Metab. 2003;88:5109-15. Armstrong, David. The Child Abuse Contrarian. ProPublica. September 16, 2018.Irwig MS, Kyinn M, Shefa MC. Financial Conflicts of Interest Among Authors of Endocrine Society Clinical Practice Guidelines. J Clin Endocrinol Metab. 2018;103:4333-38. Demay MB, Pittas AG, Bikle DD, et al. Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2024;109:1907-47.McCartney CR, McDonnell ME, Corrigan MD, et al. Vitamin D Insufficiency and Epistemic Humility: An Endocrine Society Guideline Communication. J Clin Endocrinol Metab. 2024; 109:1948–54.See our detailed notes hereKristin and Regina’s online coursesDemystifying Data: A Modern Approach to Statistical Understanding Clinical Trials: Design, Strategy, and AnalysisMedical Statistics Certificate Program Writing in the SciencesEpidemiology and Clinical Research Graduate Certificate ProgramPrograms that we teach in:Epidemiology and Clinical Research Graduate Certificate Program Find us on:Kristin - LinkedIn & Twitter/XRegina - LinkedIn...
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    1 Std. und 29 Min.
  • The Batman Effect: Do weird surprises make people nicer?

    The Batman Effect: Do weird surprises make people nicer?
    Dec 15 2025

    Description

    Nobody expects Batman—but when he shows up in a crowded subway car, are people suddenly more likely to help a passenger in need? This week on Normal Curves, we unpack a recent quasi-experimental field study involving a caped superhero costume, a prosthetic pregnancy belly, and some puzzled Italian commuters. Along the way, we demystify three common ways of describing effects for binary outcomes—risk differences, risk ratios, and odds ratios—and explain what they actually mean in plain language. We also do some statistical sleuthing, uncover a major problem hiding in the paper’s numbers, and debate what really counts as an effective Batman outfit.



    Statistical topics

    • absolute vs relative effects
    • binary outcomes
    • coding errors
    • data errors and quality control
    • effect size interpretation
    • field experiments
    • odds
    • odds ratios
    • percentage differences
    • quasi-experimental studies
    • risk differences
    • risk ratios
    • statistical sleuthing

    Methodological morals

    • “We love an uncluttered paper, but when it's missing the basics, it's like an empty fridge. Clean, yes, but dinner is not happening.”
    • “Before you make a fancy model, make sure the numbers in the table in the text match.”


    References

    • Pagnini F, Grosso F, Cavalera C, et al. Unexpected events and prosocial behavior: the Batman effect. Npj Ment Health Res. 2025;4(1):57. Published 2025 Nov 3. doi:10.1038/s44184-025-00171-5
    • PubPeer. Comments on “Unexpected events and prosocial behavior: the Batman effect.” Accessed December 2025.
    • Sainani KL. Understanding odds ratios. PM R. 2011;3(3):263-267. doi:10.1016/j.pmrj.2011.01.009
    • Nuzzo RL. Communicating measures of relative risk in plain English. PM R. 2022;14(2):283-287. doi:10.1002/pmrj.12761
    • Sainani KL. How statistics can mislead. Am J Public Health. 2012;102:e3-4.



    Kristin and Regina’s online courses:

    Demystifying Data: A Modern Approach to Statistical Understanding

    Clinical Trials: Design, Strategy, and Analysis

    Medical Statistics Certificate Program

    Writing in the Sciences

    Epidemiology and Clinical Research Graduate Certificate Program

    Programs that we teach in:

    Epidemiology and Clinical Research Graduate Certificate Program


    Find us on:

    Kristin - LinkedIn & Twitter/X

    Regina - LinkedIn & ReginaNuzzo.com


    • (00:00) - Intro
    • (03:42) - Why would Batman make people nicer?
    • (07:33) - How they ran the experiment
    • (17:06) - Did Batman save the day? Different ways to answer that
    • (22:16) - What are odds and odds ratios?
    • (29:16) - Where people get it wrong
    • (34:08) - The plot twist: big numerical errors
    • (40:36) - Did men or women give up their seat more often?
    • (43:05) - Wrap-up and methodological morals
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    47 Min.
  • Holiday Survival Guide Part 2: The survey study edition

    Holiday Survival Guide Part 2: The survey study edition
    Dec 1 2025

    Does the temperature of your coffee six months ago really predict whether you feel gassy today? This week we dissect a new nutrition survey study on hot and cold beverage habits that claims to connect drink temperature with gut symptoms, anxiety, and more—despite relying on year-old memories and a blizzard of statistical tests. It’s the perfect case study for our Holiday Survival Guide Part 2, where we teach you how to talk with Uncle Joe at the dinner table about one of the most common—and most fraught—study designs in science: cross-sectional surveys. We walk through our easy checklist for making sense of results, show how recall bias and measurement error can skew the story, and reacquaint you with nonmonogamous Multiple-Testing Dude, who’s been very busy in this dataset. A friendly, practical guide to spotting when researchers are just torturing the data until it confesses.


    Statistical topics

    • Confounding
    • Cross-sectional studies
    • False positives
    • Measurement error
    • Multiple testing
    • PICOT / PIVOT framework
    • Recall bias
    • Research hypotheses
    • Sample size and power
    • Signal vs. noise
    • SMART framework
    • Statistical significance
    • Subgroup analyses
    • Survey design
    • Transparency and trustworthiness


    Methodological morals

    • “When your measurement starts with ‘think back to last winter’ you might as well use a random number generator.”
    • “If the effect is only significant in certain subgroups in certain seasons for certain outcomes, it might just be a bad case of gas.”



    References

    • Wu T, Doyle C, Ito J, et al. Cold Exposures in Relation to Dysmenorrhea among Asian and White Women. Int J Environ Res Public Health. 2023;21(1):56. Published 2023 Dec 30. doi:10.3390/ijerph21010056
    • Wu T, Ramesh N, Doyle C, Hsu FC. Cold and hot consumption and health outcomes among US Asian and White populations. Br J Nutr. Published online September 18, 2025. doi:10.1017/S000711452510514X



    Kristin and Regina’s online courses:

    Demystifying Data: A Modern Approach to Statistical Understanding

    Clinical Trials: Design, Strategy, and Analysis

    Medical Statistics Certificate Program

    Writing in the Sciences

    Epidemiology and Clinical Research Graduate Certificate Program

    Programs that we teach in:

    Epidemiology and Clinical Research Graduate Certificate Program


    Find us on:

    Kristin - LinkedIn & Twitter/X

    Regina - LinkedIn & ReginaNuzzo.com


    • (00:00) - Intro
    • (04:36) - Did they have real research hypotheses?
    • (10:29) - Observational or randomized experiment?
    • (20:09) - PICOT and PIVOT
    • (26:20) - Memory problems
    • (32:03) - Five outcomes and measurement problems therein
    • (36:56) - SMART
    • (41:50) - Multiple Testing Dude is having a great time
    • (52:36) - How big is the effect?
    • (59:06) - Wrap-up and Irish Coffee rating scale
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    1 Std. und 4 Min.
  • Holiday Survival Guide: How to talk about scientific studies around the dinner table

    Holiday Survival Guide: How to talk about scientific studies around the dinner table
    Nov 17 2025

    Does a little alcohol really make you speak a foreign language better? This week we unpack a quirky randomized trial that tested Dutch pronunciation after a modest buzz—and came to the opposite conclusion the researchers expected. We use it as the perfect holiday case study: instead of arguing with Uncle Joe at the dinner table, we’ll show you how to pull apart a scientific headline using a friendly, practical checklist anyone can learn. Along the way we stress-test the study’s claims, take a quick detour into what a .04% buzz actually looks like, and run our own before-and-after experiment with two brave science journalists at the ScienceWriters2025 conference in Chicago. A holiday survival guide with vodka tonics, statistical sleuthing, and a few surprisingly smooth French phrases.

    Statistical topics

    • Alternative explanations
    • Arithmetic consistency / GRIM test
    • Blinding
    • Effect size / magnitude
    • Generalizability / external validity
    • Observational studies vs. experiments
    • Outcome measurement
    • PICOT framework
    • Placebo and expectancy effects
    • Primary outcomes / pre-specification
    • Randomized controlled trials
    • Research hypotheses
    • Sample size
    • SMART framework
    • Statistical significance (signal vs. noise)
    • Transparency and trustworthiness


    Methodological morals

    • “​​You don't need a PhD to read a study. Just remember, PICOT and SMART.”
    • “A decimal point can mean the difference between life and death. Details matter.”

    References

    • Renner F, Kersbergen I, Field M, Werthmann J. Dutch courage? Effects of acute alcohol consumption on self-ratings and observer ratings of foreign language skills. J Psychopharmacol. 2018;32(1):116-122. doi:10.1177/0269881117735687



    Kristin and Regina’s online courses:

    Demystifying Data: A Modern Approach to Statistical Understanding

    Clinical Trials: Design, Strategy, and Analysis

    Medical Statistics Certificate Program

    Writing in the Sciences

    Epidemiology and Clinical Research Graduate Certificate Program

    Programs that we teach in:

    Epidemiology and Clinical Research Graduate Certificate Program


    Find us on:

    Kristin - LinkedIn & Twitter/X

    Regina - LinkedIn & ReginaNuzzo.com

    • (00:00) - Intro
    • (03:30) - Uncle Joe and the question of alcohol
    • (07:20) - Randomized controlled trial
    • (10:10) - PICOT mnemonic
    • (15:43) - Just how drunk?
    • (22:25) - Boring non-placeb
    • (33:13) - Kristin’s SMART mnemonic
    • (39:32) - How big of an effect?
    • (50:46) - Two science journalists walk into a bar
    • (57:00) - Martini scale and wrap-up
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    1 Std. und 2 Min.
  • Shingles Shot and Dementia: Could one vaccine protect your brain?

    Shingles Shot and Dementia: Could one vaccine protect your brain?
    Nov 3 2025

    What do chickenpox and shingles have to do with your brain? This week, we dig into two 2025 headline-grabbing studies that link the shingles shot to lower dementia rates. We start in Wales, where a birthday cutoff turned into the perfect natural experiment, and end in the U.S. with a multi-million-person megastudy. Featuring bias-variance Goldilockses, Fozzy-the-Bear regression discontinuities, a Barbie-versus-Oppenheimer showdown for propensity scores – and the hottest rebrand of inverse-probability weighting you’ll ever hear.


    Statistical topics

    • Absolute vs. relative risk
    • Bias–variance tradeoff
    • Causal inference
    • Censoring
    • Confounding
    • Fuzzy regression discontinuity design
    • Healthy-user bias
    • Inverse probability of treatment weighting (IPTW)
    • Longitudinal study
    • Natural experiment
    • Negative controls
    • Optimal bandwidth
    • Propensity scores
    • Selection bias
    • Subgroup analysis
    • Triangular kernel weights


    Methodological morals

    • “Propensity scores are the lipstick you put on observational pigs.”
    • “Natural experiments are a hot flirtation date with causality.”



    References

    • Eyting M, Xie M, Michalik F, Heß S, Chung S, Geldsetzer P. A natural experiment on the effect of herpes zoster vaccination on dementia. Nature. 2025 May;641(8062):438-446. doi: 10.1038/s41586-025-08800-x. Epub 2025 Apr 2. PMID: 40175543; PMCID: PMC12058522.
    • Polisky V, Littmann M, Triastcyn A, et al. Varicella-zoster virus reactivation and the risk of dementia. Nat Med. Published online October 6, 2025. doi:10.1038/s41591-025-03972-5
    • Sainani KL. Propensity scores: uses and limitations. PM&R 2012; 4:693-97.


    Detailed Show Notes Page


    Kristin and Regina’s online courses:

    Demystifying Data: A Modern Approach to Statistical Understanding

    Clinical Trials: Design, Strategy, and Analysis

    Medical Statistics Certificate Program

    Writing in the Sciences

    Epidemiology and Clinical Research Graduate Certificate Program

    Programs that we teach in:

    Epidemiology and Clinical Research Graduate Certificate Program


    Find us on:

    Kristin - LinkedIn & Twitter/X

    Regina - LinkedIn & ReginaNuzzo.com


    • (00:00) - Intro and first gratuitous mention of sex
    • (03:56) - What are shingles, chickenpox, and the vaccines against them?
    • (12:30) - Fun facts about the varicella zoster and herpes viruses
    • (18:00) - A natural experiment in Wales
    • (21:54) - What is the Goldilocks optimal bandwidth?
    • (26:17) - Fuzzy regression discontinuity design demystified
    • (32:43) - Shingles vaccine vs dementia showdown
    • (34:13) - Absolute risk reduction paradox
    • (37:44) - Effects for men and women differ
    • (41:07) - A giant longitudinal study
    • (47:51) - Propensity scores demystified via Barbie and Oppenheimer
    • (53:55) - Using propensity scores to make matches
    • (58:08) - Inverse probability of treatment weighting demystified via more Barbenheimer
    • (01:02:27) - Attempts to rename IPTW for TikTok
    • (01:05:59) - Longitudinal study results
    • (01:10:00) - Smooch ratings and methodological morals: pigs and hot dates
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    1 Std. und 13 Min.
  • Scary Bridge Study: Can fear make you horny?

    Scary Bridge Study: Can fear make you horny?
    Oct 20 2025
    What if a haunted house makes your date look hotter? This week we dive into the infamous Scary Bridge Study — the 1970s classic that launched a thousand pop-psych takes on fear and lust. It’s the one with the swaying bridge, pretty “research assistant,” and phone number scrawled on torn paper. The study became legend, but how sturdy were its stats? We retrace the design, redo the numbers, and see how many math errors it takes to sway a suspension bridge. Along the way we find an erotic-fiction writing exercise, Adventure Dudes choosing their own experimental groups, and snarky replicators who tried (and failed) to make fear sexy again. We wrap with what the latest research says about when fear really does boost attraction — and when it backfires spectacularly. A Halloween story of danger, desire, and unconscious sexual drive. This episode has a video version! https://www.youtube.com/watch?v=2coWoS_3460Statistical topicsArithmetic checksChi-square testConfoundersGRIM testInter-rater reliabilityMeta-analysisNegative controlRandomizationReplication Sample sizeSignal vs. noiseStatistical sleuthingSubjective measurementT-testMethodological morals“Those who don't verify their numbers dig their own statistical graves.”“Famous doesn't mean flawless.”ReferencesBrown, NJ, Heathers, JA. The GRIM test: A simple technique detects numerous anomalies in the reporting of results in psychology. Social Psychological and Personality Science. 2017; 8(4):363-369.Dutton DG, Aron AP. Some evidence for heightened sexual attraction under conditions of high anxiety. J Pers Soc Psychol. 1974;30(4):510-517. doi:10.1037/h0037031Foster CA, Witcher BS, Campbell WK, Green JD. Arousal and attraction: Evidence for automatic and controlled processes. J Pers Soc Psychol. 1998;74(1):86-101.Kenrick DT, Cialdini R, Linder D. Misattribution under fear-producing circumstances: Four failures to replicate. Pers Soc Psychol Bull. 1979;5(3):329-334.van der Zee T, Anaya J, Brown NJL. Statistical heartburn: an attempt to digest four pizza publications from the Cornell Food and Brand Lab. BMC Nutr. 2017;3:54. Published 2017 Jul 10. doi:10.1186/s40795-017-0167-xhttp://www.prepubmed.org/grim_test/Kristin and Regina’s online courses: Demystifying Data: A Modern Approach to Statistical Understanding Clinical Trials: Design, Strategy, and Analysis Medical Statistics Certificate Program Writing in the Sciences Epidemiology and Clinical Research Graduate Certificate Program Programs that we teach in:Epidemiology and Clinical Research Graduate Certificate Program Find us on:Kristin - LinkedIn & Twitter/XRegina - LinkedIn & ReginaNuzzo.com(00:00) - Intro: Fear and Flirtation on a Suspension Bridge (05:40) - A Classic 1970s Experiment with No IRB to be Found (11:15) - Adventure Dudes Choose Their Own Bridge (17:00) - The Sexy Story Scale (22:20) - Cool Factor and the Negative Control (28:54) - Grim Reaper Math (36:29) - T-Tests, Chi-Squares, and Shaky Results (42:44) - Electric Shocks and Damsels in Distress (50:49) - Replications and Rejections (58:39) - Wrap-Up, Methodological Morals, and a New Sexy Rating Scale
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    1 Std. und 5 Min.
  • Ultramarathons: Can vitamin D protect your bones?

    Ultramarathons: Can vitamin D protect your bones?
    Oct 6 2025
    Ultramarathoners push their bodies to the limit, but can a giant pre-race dose of vitamin D really keep their bones from breaking down? In this episode, we dig into a trial that tested this claim – and found a statistical endurance event of its own: six highly interchangeable papers sliced from one small study. Expect missing runners, recycled figures, and a peer-review that reads like stand-up comedy, plus a quick lesson in using degrees of freedom as your statistical breadcrumbs.Statistical topicsData cleaning and validationDegrees of freedomExploratory vs confirmatory analysisFalse positives and Type I errorIntention-to-treat principleMultiple testingOpen data and transparencyP-hackingSalami slicingParametric vs non-parametric testsPeer review qualityRandomized controlled trialsResearch reproducibilityStatistical sleuthingMethodological morals“Degrees of freedom are the breadcrumbs in statistical sleuthing. They reveal the sample size even when the authors do not.”“Publishing the same study again and again with only the outcomes swapped is Mad Libs Science, better known as salami slicing.”ReferencesBoswell, Rachel. Pre-race vitamin D could do wonders for ultrarunners’ bone health, according to science. Runner’s World. September 25, 2025. Mieszkowski J, Stankiewicz B, Kochanowicz A, et al. Ultra-Marathon-Induced Increase in Serum Levels of Vitamin D Metabolites: A Double-Blind Randomized Controlled Trial. Nutrients. 2020;12(12):3629. Published 2020 Nov 25. doi:10.3390/nu12123629Mieszkowski J, Borkowska A, Stankiewicz B, et al. Single High-Dose Vitamin D Supplementation as an Approach for Reducing Ultramarathon-Induced Inflammation: A Double-Blind Randomized Controlled Trial. Nutrients. 2021;13(4):1280. Published 2021 Apr 13. doi:10.3390/nu13041280Mieszkowski J, Brzezińska P, Stankiewicz B, et al. Direct Effects of Vitamin D Supplementation on Ultramarathon-Induced Changes in Kynurenine Metabolism. Nutrients. 2022;14(21):4485. Published 2022 Oct 25. doi:10.3390/nu14214485Mieszkowski J, Brzezińska P, Stankiewicz B, et al. Vitamin D Supplementation Influences Ultramarathon-Induced Changes in Serum Amino Acid Levels, Tryptophan/Branched-Chain Amino Acid Ratio, and Arginine/Asymmetric Dimethylarginine Ratio. Nutrients. 2023;15(16):3536. Published 2023 Aug 11. doi:10.3390/nu15163536Stankiewicz B, Mieszkowski J, Kochanowicz A, et al. Effect of Single High-Dose Vitamin D3 Supplementation on Post-Ultra Mountain Running Heart Damage and Iron Metabolism Changes: A Double-Blind Randomized Controlled Trial. Nutrients. 2024;16(15):2479. Published 2024 Jul 31. doi:10.3390/nu16152479Stankiewicz B, Kochanowicz A, et al. Single high-dose vitamin D supplementation impacts ultramarathon-induced changes in serum levels of bone turnover markers: a double-blind randomized controlled trial. J Int Soc Sports Nutr. 2025 Dec;22(1):2561661. doi: 10.1080/15502783.2025.2561661.Kristin and Regina’s online courses: Demystifying Data: A Modern Approach to Statistical Understanding Clinical Trials: Design, Strategy, and Analysis Medical Statistics Certificate Program Writing in the Sciences Epidemiology and Clinical Research Graduate Certificate Program Programs that we teach in:Epidemiology and Clinical Research Graduate Certificate Program Find us on:Kristin - LinkedIn & Twitter/XRegina - LinkedIn & ReginaNuzzo.com 00:00 Intro & claim of the episode 00:44 Runner’s World headline: Vitamin D for ultramarathoners 02:03 Kristin’s connection to running and vitamin D skepticism 03:32 Ultramarathon world—Regina’s stories and Death Valley race 06:29 What ultramarathons do to your bones 08:02 Boy story: four stress fractures in one race 10:00 Study design—40 male runners in Poland 11:33 Missing flow diagram and violated intention-to-treat 13:02 The intervention: 150,000 IU megadose 15:09 Blinding details and missing randomization info 17:13 Measuring bone biomarkers—no primary outcome specified 19:12 The wrong clinicaltrials.gov registration 20:35 Discovery of six papers from one dataset (salami slicing) 23:02 Why salami slicing misleads readers 25:42 Inconsistent reporting across papers 29:11 Changing inclusion criteria and sloppy methods 31:06 Typos, Polish notes, and misnumbered references 32:39 Peer review comedy gold—“Please define vitamin D” 36:06 Reviewer laziness and p-hacking admission 39:13 Results: implausible bone growth mid-race 41:16 Degrees of freedom sleuthing reveals hidden sample sizes 47:07 Open data? Kristin emails the authors 48:42 Lessons from Kristin’s own ultramarathon dataset 51:22 Fishing expeditions and misuse of parametric tests 53:07 Strength of evidence: one smooch each 54:44 Methodologic morals—Mad Libs Science & degrees of freedom breadcrumbs 56:12 Anyone can spot red flags—trust your eyes 57:34 Outro: skip the vitamin D shot before your next run
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    59 Min.