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

Can you really sit on your couch, pop vitamin D pills, and shave seconds off your 5k? Touted as a miracle cure-all, vitamin D is claimed to slash cancer and infection risks while boosting mood, cognition, and athletic performance. But does upping your vitamin D really make you healthier and happier? In this episode, we’ll follow the epidemiologic evidence—from clues in petri dishes through randomized trials. Along our journey, we’ll encounter chocolate-fueled Nobel Prizes, rock stars, pasty Brits, and a tangled mess of promiscuous variables.

Statistical topics

• ecological studies
• ecological fallacy
• correlation is not causation
• observational studies
• statistical adjustment
• confounding
• randomized trials
• factorial design
• post-hoc analyses
• subgroup analyses

Methodologic morals

• “Variables with too many entanglements make observational studies a fool’s game.”
• “If your intervention works only when you torture your data, it’s probably a false confession.”

Citations

Garland CF, Garland FC. Do sunlight and vitamin D reduce the likelihood of colon cancer? Int J Epidemiol. 1980;9:227-31.

Messerli FH. Chocolate consumption, cognitive function, and Nobel laureates. N Engl J Med. 2012;367:1562-64.

Holick, MF. The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problems. Penguin Publishing Group, 2011. 

McMillan A. Can vitamin D boost your fitness routine? Dec 18, 2018.

Marawan A, Kurbanova N, Qayyum R. Association between serum vitamin D levels and cardiorespiratory fitness in the adult population of the USA. Eur J Prev Cardiol. 2019;26:750-55.

Vitamin D levels in the blood linked to cardiorespiratory fitness. European Society of Cardiology. Oct 30, 2018.

Jones AM, Kirby BS, Clark IE, et al. Physiological demands of running at 2-hour marathon race pace. J Appl Physiol. 2021;130:369-79.

Manson JE, Bassuk SS, Lee IM, et al. The VITamin D and OmegA-3 TriaL (VITAL): rationale and design of a large randomized controlled trial of vitamin D and marine omega-3 fatty acid supplements for the primary prevention of cancer and cardiovascular disease. Contemp Clin Trials. 2012;33:159-71.

Manson JE, Cook NR, Lee IM, et al. Vitamin D supplements and prevention of cancer and cardiovascular disease. NEJM. 2019;380:33-44.

Lee KL, McNeer JF, Starmer CF, et al. Clinical judgment and statistics: lessons from a simulated randomized trial in coronary artery disease. Circulation. 1980; 61:508-15.

Wood S. VITAL: No Benefits to Vitamin D and Omega-3s in Reducing Major CV Events, Cancer. TCTMD.com. Nov 10, 2018.

Neale RE, Baxter C, Romero BD, et al. The D-Health Trial: a randomised controlled trial of the effect of vitamin D on mortality. Lancet Diabetes Endocrinol. 2022