We're learning more about what Vitamin D does

Original Article ↗ Hacker News Discussion ↗

Vitamin D dosing, deficiency, and toxicity

  • Multiple anecdotes of clinically low vitamin D, with doctors recommending anywhere from 800–2,000 IU/day up to 50,000 IU/day for short “repletion” periods.
  • Strong disagreement on what counts as “a lot”: some call 4,000 IU/day “perfect” and commonly sold; others report that similar doses pushed their blood levels too high.
  • Several emphasize that toxicity is rare and usually requires very high, long-term dosing; others report adverse symptoms (chest pain, palpitations, sleep disruption) even at 1,000–5,000 IU and stress individual variability.
  • Broad consensus that dosage should be guided by blood tests; “one-size-fits-all” advice is criticized.

Supplements, prescriptions, and health-system economics

  • UK context: doctors may avoid prescribing vitamin D because OTC is cheaper than the flat prescription charge; in Scotland/Wales prescriptions are free.
  • Some calculate that giving everyone supplements would be a small fraction of NHS budget and likely cost-effective if deficiency meaningfully harms health.
  • Others note logistics, bureaucracy, and that fortifying foods (as with US milk and rickets) might be a better systemic approach.

Sunlight, latitude, and skin-cancer trade-offs

  • Experiences from tropics and Australia: strict “avoid the sun” advice can produce deficiency even where UV is abundant.
  • Debate over how risky sun exposure really is: some argue modern messaging overstates danger; others, citing high skin-cancer rates and personal surgery, say this is dangerous minimization.
  • Several distinguish brief, regular non-burning exposure from intermittent, intense sunburns, which are seen as the main melanoma driver in some cited work.
  • Practical tips include short daily exposure, hats/UPF clothing instead of heavy sunscreen, or using tanning beds/UV lamps in high latitudes.

Co-nutrients, genetics, and individual differences

  • Frequent mention of pairing vitamin D with K2, magnesium, and monitoring calcium; one user with genetic variants (CYP2R1, CALCA) found supplements caused hypercalcemia and instead relies on salmon.
  • General theme: genetics, skin color, latitude, and lifestyle strongly affect needs and responses, reinforcing the “test, don’t guess” message.

Experiences, mechanisms, and evidence quality

  • Several report dramatic improvements in mood, energy, and “malaise” after correcting deficiency; others notice effects on sleep or vivid dreams (possibly confounded by ingredients like glycerin).
  • Some commenters say the research shows only small, mixed effects and caution against overhyping vitamin D as a cure-all.
  • Others argue there are well-established benefits and point to claims that official RDAs may be off by an order of magnitude; they criticize slow correction of guideline errors.
  • One detailed but speculative thread links dust-mite exposure, immune damage, high IgE, and low vitamin D; others request stronger causal evidence.

Study design and ethics

  • A proposal to use prison populations for tightly controlled vitamin D/diet trials is firmly rejected by others, citing ethical frameworks (Nuremberg, Belmont, Helsinki) and US regulations that treat prisoners as a vulnerable group.