vitamin
Vitamin D
Cholecalciferol, the most bioavailable form of vitamin D. Essential for calcium absorption, bone health, immune function, and mood regulation. Synthesized in the skin upon sun exposure.
What it’s good for
Vitamin D for Slow Recovery
Strong3 studies · 3 supporting · 0 against
12 safety notes
Recovering from hard training is mostly immune work, and vitamin D helps steer it.
Dose: 2000–4000 IU
Tested as: Vitamin D3 at 3,000 IU/day for wound healing in hospitalised patients with severe burns (one RCT); broader wound-healing evidence uses unspecified vitamin D forms in clinical populations
Vitamin D for Frequent Colds
Solid2 studies · 1 supporting · 0 against
12 safety notes
Switches on the front line of your immune defences, and keeps the response from overshooting.
Dose: 2000–4000 IU
Tested as: vitamin D supplementation — a mix of D2 and D3 preparations across the 25 pooled trials; D3-specific effect not confirmed as the primary finding
Vitamin D for Chronic Inflammation
Mixed3 studies · 2 supporting · 1 against
13 safety notes
Steers your immune system away from its inflammatory setting and toward its calming one.
Dose: 2000–4000 IU
Tested as: vitamin D supplementation — D3 versus D2 not confirmed in any cited trial
Vitamin D for Chronic Fatigue
Mixed2 studies · 1 supporting · 1 against
12 safety notes
Muscle cells carry vitamin D receptors, and low levels are linked with the inflammation that drives tiredness.
Dose: 2000–4000 IU
Vitamin D for Hair Thinning
Evidence1 study · 1 supporting · 0 against
13 safety notes
Hair follicles carry vitamin D receptors and need them to start a new growth phase.
Dose: 2000–4000 IU
Vitamin D for Joint Pain
No Benefit5 studies · 2 supporting · 2 against
12 safety notes
How it was tested: Adults with symptomatic knee OA were randomized to 2000 IU Vitamin D3 daily or placebo for two years. Neither knee pain scores nor cartilage volume loss differed between groups at the end of the trial. Both groups improved slightly, but the supplement provided no additional benefit over placebo.
Vitamin D governs calcium in cartilage and steers the immune activity inside a joint.
Dose: 2000–4000 IU
Vitamin D for Low Mood
No Benefit2 studies · 1 supporting · 1 against
12 safety notes
How it was tested: A 5-year trial in 18,353 adults found it did not reduce depression or lift mood.
Vitamin D receptors sit throughout the brain, including the regions that set mood.
Dose: 2000–4000 IU
Vitamin D for Back Pain
No Benefit1 study · 0 supporting · 1 against
12 safety notes
How it was tested: A 2024 pooled analysis of 10 trials found no meaningful reduction in long-term back pain.
Serious vitamin D deficiency softens bone and causes aching, which is the starting point for the claim.
Dose: 2000–4000 IU
Tested as: vitamin D supplementation — D3 versus D2 not confirmed in cited trial