Vitamin D2 (ergocalciferol)

Tier 2 — promising · Bone · Immunity · Vegan source

The plant-derived form of vitamin D, obtained from UV-irradiated mushrooms or yeast. Multiple trials show D2 is less effective than D3 at raising and maintaining blood vitamin D levels. The Tripkovic et al. 2012 AJCN meta-analysis (confirmed by Tripkovic 2017 RCT) found D3 raises 25-OH-D levels substantially more effectively than D2 at equivalent doses. The only advantage of D2 is that it is suitable for strict vegans. If vegan, consider vegan-sourced D3 from lichen as a better alternative.

Dose: 1,000–2,000 IU/day; D3 is significantly more effective — use D2 only if vegan D3 is unavailable