We are not in a low vitamin D epidemic, with Regina Nuzzo PhD & Kristin Cobb PhD

Is everyone really low in vitamin D? Or have we been sold a narrative that doesn’t hold up under scrutiny?

In this mind-blowing episode, Tara sits down with Regina and Kristin, the investigative duo behind the Normal Curves podcast, to explore the truth behind the so-called “vitamin D deficiency epidemic.” Spoiler: it may have been manufactured by outdated, flawed science—and driven by people with major conflicts of interest.

This is a must-listen for anyone taking vitamin D or worried about their levels. If you’ve been told your D is “low,” this episode might change everything.

In this episode we cover:

• How the original vitamin D reference ranges were set (and how they were quietly reversed in 2024)

• Why testing vitamin D routinely may be doing more harm than good

• The role of conflicts of interest in shaping clinical guidelines

• What the latest randomized controlled trials (RCTs) actually show about supplementing vitamin D for disease prevention

• Why observational data can mislead us, and how low D might be the consequence—not the cause—of illness

• How much sun you actually need to make enough vitamin D (hint: it’s a lot less than you think)

• Why the “low D” narrative stuck around even after the science was overturned

If you're thinking about taking D, already taking D, or have been told your vitamin D is “low” (it likely isn't) then this one is for you.

Regina Nuzzo is a Gallaudet professor, award-winning science journalist, and co-host of the Normal Curves podcast. She brings statistics to life for students and audiences worldwide, often using sex-science examples to keep things lively. Her writing has appeared in Nature, The New York Times, Scientific American, and the Los Angeles Times, where she wrote a column on the science of sex and relationships. Alongside co-host Kristin Sainani, she penned a long-running statistics column for Physical Medicine & Rehabilitation and now teaches a Stanford summer course on statistics for clinical informatics. Regina's work earned the American Statistical Association's Excellence in Statistical Reporting Award.

Kristin Cobb Sainani is a Stanford professor, science journalist, and co-host of the Normal Curves podcast. She brings statistics and scientific writing to students and audiences around the world. She also works as a statistician on sports medicine projects. Kristin has written widely about health, science, and statistics for both academic and popular audiences. She was a health columnist for Allure magazine for ten years and, alongside co-host Regina Nuzzo, penned a long-running statistics column for the journal Physical Medicine & Rehabilitation. In 2018, she received Stanford's Biosciences Award for Excellence in Graduate Teaching. Known for her statistical sleuthing and ability to cut through academic jargon, Kristin champions clear language and rigorous methods in science.

Normal Curves Podcast

Mentioned in this episode:

🔍 Formula to convert your 25,OH,D leve from ng/dL to nmol/L:  25(OH)D in nmol/L = 25(OH)D in ng/dL X 25

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