Normal Curves: Sexy Science, Serious Statistics

Vitamin D Part 2: Good for more than just your bones?

4 snips
Mar 24, 2025
Can vitamin D really boost your athletic performance while slashing cancer risks? The hosts delve into claims of this miracle vitamin, discussing studies that tease out the truth. They tackle the challenges of observational studies and ecological fallacies, revealing how misleading correlations can be. Even promising trials, like VITAL, show no major benefits after rigorous testing. Their journey underscores that while vitamin D is essential for bones, more doesn't always mean better health, urging caution in supplementation.
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ANECDOTE

Fitness Study That Made Headlines

  • A 2019 study linked higher blood vitamin D with higher VO2 max in young adults, reporting a ~4.3 point mean difference.
  • The media framed it causally, implying pills could boost fitness.
INSIGHT

Exercise As The Obvious Confounder

  • The VO2 max association likely reflected unmeasured exercise: outdoor exercisers have both higher fitness and more sun exposure.
  • Unmeasured confounding can produce plausible but noncausal biological stories.
INSIGHT

Vitamin D Is A 'Promiscuous' Variable

  • Vitamin D links to many health factors (obesity, activity, kidney function), creating a tangled network of associations.
  • Statistical adjustment struggles to untangle such a promiscuous variable.
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