There is not yet an agreed upon “optimal” Vitamin D level in the scientific community. This mostly comes from a disagreement on “deficiency” (Taylor C, et al. 2018) vs “optimal” blood levels (Holick MF. 2017) and what endpoint is being considered, i.e. bone health vs. infection risk. At OmegaQuant, we recommend aiming for a level of at least 30 ng/mL. The evidence for the 30 ng/mL cut off is demonstrated by Garland et al. 2014 where the hazard ratio for mortality plateaus around 30 ng/mL, by Michaelsson et al. 2010 where the lowest risk for death from all-causes, cancer and cardiovascular disease is at 30 ng/mL, by Ginde et al. 2009 where those with levels >30 ng/mL have the lowest risk of upper respiratory tract infections, and by Miliku et al. 2016 where pregnant women with levels >30 ng/mL were at the lowest risk of preterm birth, as well as babies born with low birth weight and small for gestational age. This seems like an excellent target level for several different populations and health states.
You may notice that none of these outcomes are related to bone health (rickets in kids and osteoporosis/hip fracture risk in adults), the primary health outcome related to a deficiency in Vitamin D. For this endpoint, according to the Institute of Medicine, a serum level of >20 ng/mL is considered sufficient and <12.5 ng/mL is deficient. From OmegaQuant’s perspective, optimal vitamin D levels are considered more from a “whole health” perspective rather than specific to bone health, thus the higher target of at least 30 ng/mL.